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Coutinho Pereira CF, Borges BGAL, Sousa KRA, Holakoei S, Roman LS, Araujo CM, Cremona M, Koehler M, Marchiori CFN, Rocco MLM. Inducing molecular orientation in solution-processed thin films of fluorene-bithiophene-based copolymer: thermal annealing vs. solvent additive. RSC Adv 2024; 14:9051-9061. [PMID: 38500615 PMCID: PMC10945741 DOI: 10.1039/d3ra08066h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Accepted: 02/22/2024] [Indexed: 03/20/2024] Open
Abstract
A deep understanding of the factors influencing the morphology of thin films based on conjugated polymers is essential to boost their performance in optoelectronic devices. Herein, we investigated the electronic structure and morphology of thin films of the copolymer poly(9,9-dioctyl-fluorenyl-co-bithiophene) (F8T2) in its pristine form as well as samples processed with the solvent additive 1,8-diiodooctane (DIO) or post-processed through thermal annealing treatment. Measurements were carried out using angle-resolved S K-edge NEXAFS (near-edge X-ray absorption fine structure) in total electron yield (TEY) and fluorescence yield (FY) detection modes. Two main transitions were observed at the S 1s NEXAFS spectra: S 1s → π* and S 1s → σ* (S-C). The observed dichroism pointed to a face-on orientation of the conjugated backbone, which was significantly increased for F8T2 films processed with DIO. Resonant Auger decay spectra were obtained and analyzed using the core-hole clock (CHC) method. An enhancement in the charge transfer process was observed for thermally annealed films, especially for samples processed with DIO, corresponding to an increase in film ordering. Furthermore, the investigated films were characterized using X-ray photoelectron spectroscopy, attesting to the presence of the thiophene unit in the samples and demonstrating that some of its sulfur atoms were positively polarized in the F8T2 films. All these experimental findings were compared with molecular dynamics (MD) simulations of film evaporation with and without DIO. The use of MD, together with mathematical modeling, was able to explain the major effects found in the experiments, including the polarization of sulfur atoms. The simultaneous use of powerful spectroscopic techniques and theoretical methods shed light on key aspects linking film morphology with fabrication procedures.
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Affiliation(s)
| | - Bruno G A L Borges
- Institute of Chemistry, Federal University of Rio de Janeiro (UFRJ) 21941-909 Rio de Janeiro RJ Brazil
| | - Karlison R A Sousa
- Department of Physics, Federal University of Paraná (UFPR) Centro Politécnico, CP 19081 81531-900 Curitiba PR Brazil
- Fundação de Amparo à Pesquisa do Estado do Amazonas - FAPEAM 69058-030 Manaus AM Brazil
| | - Soheila Holakoei
- Institute of Chemistry, Federal University of Rio de Janeiro (UFRJ) 21941-909 Rio de Janeiro RJ Brazil
| | - Lucimara S Roman
- Department of Physics, Federal University of Paraná (UFPR) Centro Politécnico, CP 19081 81531-900 Curitiba PR Brazil
| | - C Moyses Araujo
- Department of Engineering and Physics, Karlstad University 65188 Karlstad Sweden
- Materials Theory Division, Department of Physics and Astronomy, Uppsala University 75120 Uppsala Sweden
| | - Marco Cremona
- Departamento de Física, PUC-Rio 22453-900 Rio de Janeiro RJ Brazil
| | - Marlus Koehler
- Department of Physics, Federal University of Paraná (UFPR) Centro Politécnico, CP 19081 81531-900 Curitiba PR Brazil
| | - Cleber F N Marchiori
- Department of Engineering and Physics, Karlstad University 65188 Karlstad Sweden
| | - Maria Luiza M Rocco
- Institute of Chemistry, Federal University of Rio de Janeiro (UFRJ) 21941-909 Rio de Janeiro RJ Brazil
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2
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Kozdra M, Brandell D, Araujo CM, Mace A. The sensitive aspects of modelling polymer-ceramic composite solid-state electrolytes using molecular dynamics simulations. Phys Chem Chem Phys 2024; 26:6216-6227. [PMID: 38305339 DOI: 10.1039/d3cp04617f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2024]
Abstract
Solid-state composite electrolytes have arisen as one of the most promising materials classes for next-generation Li-ion battery technology. These composites mix ceramic and solid-polymer ion conductors with the aim of combining the advantages of each material. The ion-transport mechanisms within such materials, however, remain elusive. This knowledge gap can to a large part be attributed to difficulties in studying processes at the ceramic-polymer interface, which are expected to play a major role in the overall ion transport through the electrolyte. Computational efforts have the potential of providing significant insight into these processes. One of the main challenges to overcome is then to understand how a sufficiently robust model can be constructed in order to provide reliable results. To this end, a series of molecular dynamics simulations are here carried out with a variation of certain structural (surface termination and polymer length) and pair potential (van der Waals parameters and partial charges) models of the Li7La3Zr2O12 (LLZO) poly(ethylene oxide) (PEO) system, in order to test how sensitive the outcome is to each variation. The study shows that the static and dynamic properties of Li-ion are significantly affected by van der Waals parameters as well as the surface terminations, while the thickness of the interfacial region - where the structure-dynamic properties are different as compared to the bulk-like regime - is the same irrespective of the simulation setup.
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Affiliation(s)
- Melania Kozdra
- Department of Chemistry - Ångström Laboratory, Uppsala University, Box 538, 75121 Uppsala, Sweden.
| | - Daniel Brandell
- Department of Chemistry - Ångström Laboratory, Uppsala University, Box 538, 75121 Uppsala, Sweden.
| | - C Moyses Araujo
- Department of Engineering and Physics, Karlstad University, Karlstad, Sweden
- Department of Physics and Astronomy, Materials Theory Division, Uppsala University, Box 516, 75120 Uppsala, Sweden
| | - Amber Mace
- Department of Chemistry - Ångström Laboratory, Uppsala University, Box 538, 75121 Uppsala, Sweden.
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Franco LR, Marchiori C, Araujo CM. Unveiling the impact of exchange-correlation functionals on the description of key electronic properties of non-fullerene acceptors in organic photovoltaics. J Chem Phys 2023; 159:204110. [PMID: 38018752 DOI: 10.1063/5.0163180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Accepted: 10/30/2023] [Indexed: 11/30/2023] Open
Abstract
Non-fullerene electron acceptors have emerged as promising alternatives to traditional electron-acceptors in the active layers of organic photovoltaics. This is due to their tunable energy levels, optical response in the visible light spectrum, high electron mobility, and photochemical stability. In this study, the electronic properties of two representative non-fullerene acceptors, ITIC and Y5, have been calculated within the framework of density functional theory using a range of hybrid and non-hybrid density functionals. Screened range-separated hybrid (SRSH) approaches were also tested. The results are analyzed in light of the previously reported experimental outcomes. Specifically, we have calculated the oxidation and reduction potentials, fundamental and optical gaps, the highest occupied molecular orbital and lowest unoccupied molecular orbital energies, and exciton binding energies. Additionally, we have investigated the effects of the medium dielectric constant on these properties employing a universal implicit solvent model. It was found that hybrid functionals generally perform poorly in predicting oxidation potentials, while non-hybrid functionals tend to overestimate reduction potentials. The inclusion of a large Hartree-Fock contribution to the global or long range was identified as the source of inaccuracy for many hybrid functionals in predicting both redox potentials and the fundamental and optical gaps. Corroborating with the available literature, ∼50% of all tested functionals predicted very small exciton binding energies, within the range of ±0.1 eV, that become even smaller by increasing the dielectric constant of the material. Finally, the OHSE2PBE and tHCTHhyb functionals and the optimal tuning SRSH approach emerged as the best-performing methods, with good accuracy in the description of the electronic properties of interest.
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Affiliation(s)
- Leandro R Franco
- Department of Engineering and Physics, Karlstad University, 65188 Karlstad, Sweden
| | - Cleber Marchiori
- Department of Engineering and Physics, Karlstad University, 65188 Karlstad, Sweden
| | - C Moyses Araujo
- Department of Engineering and Physics, Karlstad University, 65188 Karlstad, Sweden
- Materials Theory Division, Department of Physics and Astronomy, Uppsala University, 75120 Uppsala, Sweden
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4
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Wu J, Ling Z, Franco LR, Jeong SY, Genene Z, Mena J, Chen S, Chen C, Araujo CM, Marchiori CFN, Kimpel J, Chang X, Isikgor FH, Chen Q, Faber H, Han Y, Laquai F, Zhang M, Woo HY, Yu D, Anthopoulos TD, Wang E. On the Conformation of Dimeric Acceptors and Their Polymer Solar Cells with Efficiency over 18 . Angew Chem Int Ed Engl 2023; 62:e202302888. [PMID: 37380618 DOI: 10.1002/anie.202302888] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2023] [Revised: 06/27/2023] [Accepted: 06/28/2023] [Indexed: 06/30/2023]
Abstract
The determination of molecular conformations of oligomeric acceptors (OAs) and their impact on molecular packing are crucial for understanding the photovoltaic performance of their resulting polymer solar cells (PSCs) but have not been well studied yet. Herein, we synthesized two dimeric acceptor materials, DIBP3F-Se and DIBP3F-S, which bridged two segments of Y6-derivatives by selenophene and thiophene, respectively. Theoretical simulation and experimental 1D and 2D NMR spectroscopic studies prove that both dimers exhibit O-shaped conformations other than S- or U-shaped counter-ones. Notably, this O-shaped conformation is likely governed by a distinctive "conformational lock" mechanism, arising from the intensified intramolecular π-π interactions among their two terminal groups within the dimers. PSCs based on DIBP3F-Se deliver a maximum efficiency of 18.09 %, outperforming DIBP3F-S-based cells (16.11 %) and ranking among the highest efficiencies for OA-based PSCs. This work demonstrates a facile method to obtain OA conformations and highlights the potential of dimeric acceptors for high-performance PSCs.
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Affiliation(s)
- Jingnan Wu
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296, Göteborg, Sweden
- Department of Chemistry and Bioscience, Aalborg University, 9220, Aalborg, Denmark
| | - Zhaoheng Ling
- King Abdullah University of Science and Technology (KAUST), KAUST Solar Center, Thuwal, 23955, Saudi Arabia
| | - Leandro R Franco
- Department of Engineering and Physics, Karlstad University, 65188, Karlstad, Sweden
| | - Sang Young Jeong
- Department of Chemistry, Korea University, Seoul, 02841 (Republic of, Korea
| | - Zewdneh Genene
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296, Göteborg, Sweden
| | - Josué Mena
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296, Göteborg, Sweden
| | - Si Chen
- King Abdullah University of Science and Technology (KAUST), KAUST Solar Center, Thuwal, 23955, Saudi Arabia
| | - Cailing Chen
- Advanced Membranes and Porous Materials Center, Physical Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
| | - C Moyses Araujo
- Department of Engineering and Physics, Karlstad University, 65188, Karlstad, Sweden
- Materials Theory Division, Department of Physics and Astronomy, Uppsala University, 75120, Uppsala, Sweden
| | - Cleber F N Marchiori
- Department of Engineering and Physics, Karlstad University, 65188, Karlstad, Sweden
| | - Joost Kimpel
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296, Göteborg, Sweden
| | - Xiaoming Chang
- King Abdullah University of Science and Technology (KAUST), KAUST Solar Center, Thuwal, 23955, Saudi Arabia
| | - Furkan H Isikgor
- King Abdullah University of Science and Technology (KAUST), KAUST Solar Center, Thuwal, 23955, Saudi Arabia
| | - Qiaonan Chen
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296, Göteborg, Sweden
| | - Hendrik Faber
- King Abdullah University of Science and Technology (KAUST), KAUST Solar Center, Thuwal, 23955, Saudi Arabia
| | - Yu Han
- Advanced Membranes and Porous Materials Center, Physical Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
| | - Frédéric Laquai
- King Abdullah University of Science and Technology (KAUST), KAUST Solar Center, Thuwal, 23955, Saudi Arabia
| | - Maojie Zhang
- National Engineering Research Center for Colloidal Materials, School of Chemistry & Chemical Engineering, Shandong University, Jinan, Shandong, 250100, China
| | - Han Young Woo
- Department of Chemistry, Korea University, Seoul, 02841 (Republic of, Korea
| | - Donghong Yu
- Department of Chemistry and Bioscience, Aalborg University, 9220, Aalborg, Denmark
| | - Thomas D Anthopoulos
- King Abdullah University of Science and Technology (KAUST), KAUST Solar Center, Thuwal, 23955, Saudi Arabia
| | - Ergang Wang
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296, Göteborg, Sweden
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Franco LR, Toledo KCF, Matias TA, Araujo CM, Araki K, Coutinho K. Theoretical investigation of solvent and oxidation/deprotonation effects on the electronic structure of a mononuclear Ru-aqua-polypyridine complex in aqueous solution. Phys Chem Chem Phys 2023; 25:24475-24494. [PMID: 37655780 DOI: 10.1039/d3cp02154h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
Abstract
Mononuclear polypyridine ruthenium (Ru) complexes can catalyze various reactions, including water splitting, and can also serve as photosensitizers in solar cells. Despite recent progress in their synthesis, accurately modeling their physicochemical properties, particularly in solution, remains challenging. Herein, we conduct a theoretical investigation of the structural and electronic properties of a mononuclear Ru-aqua polypyridine complex in aqueous solution, considering five of its possible oxidation/protonation states species: [RuII(H2O)(py)(bpy)2]2+, [RuII(OH)(py)(bpy)2]+, [RuIII(H2O)(py)(bpy)2]3+, [RuIII(OH)(py)(bpy)2]2+ and [RuIV(O)(py)(bpy)2]2+, where py = pyridine and bpy = 2,2'-bipyridine. At first, we investigate the impact of proton-coupled and non-coupled electron transfer reactions on the geometry and electronic structure of the complexes in vacuum and in solution, using an implicit solvent model. Then, using a sequential multiscale approach that combines quantum mechanics and molecular mechanics (S-QM/MM), we examine the explicit solvent effects on the electronic excitations of the complexes, and compare them with the experimental results. The complexes were synthesized, and their absorption spectra measured in aqueous solution. To accurately describe the QM interactions between the metal center and the aqueous ligand in the MM simulations, we developed new force field parameters for the Ru atom. We analyze the solvent structure around the complexes and account for its explicit influence on the polarization and electronic excitations of the complexes. Notably, accounting for the explicit solvent polarization effects of the first solvation shells is essential to correctly describe the energy of the electronic transitions, and the explicit treatment of the hydrogen bonds at the QM level in the excitation calculations improves the accuracy of the description of the metal-to-ligand charge-transfer bands. Transition density matrix analysis is used to characterize all electronic transitions in the visible and ultraviolet ranges according to their charge-transfer (CT) character. This study elucidates the electronic structure of those ruthenium polypyridyl complexes in aqueous solution and underscores the importance of precisely describing solvent effects, which can be achieved employing the S-QM/MM method.
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Affiliation(s)
- Leandro Rezende Franco
- Instituto de Fisica, Universidade de Sao Paulo, Cidade Universitaria, 05508-090 Sao Paulo, SP, Brazil
- Department of Engineering and Physics, Karlstad University, 65188 Karlstad, Sweden.
| | | | - Tiago Araujo Matias
- Instituto de Quimica, Universidade de Sao Paulo, Av. Lineu Prestes 748, Butanta, 05508-000 Sao Paulo, SP, Brazil
| | - C Moyses Araujo
- Department of Engineering and Physics, Karlstad University, 65188 Karlstad, Sweden.
- Materials Theory Division, Department of Physics and Astronomy, Ångström Laboratory, Uppsala University, 75120 Uppsala, Sweden
| | - Koiti Araki
- Instituto de Quimica, Universidade de Sao Paulo, Av. Lineu Prestes 748, Butanta, 05508-000 Sao Paulo, SP, Brazil
| | - Kaline Coutinho
- Instituto de Fisica, Universidade de Sao Paulo, Cidade Universitaria, 05508-090 Sao Paulo, SP, Brazil
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6
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Zaar F, Moyses Araujo C, Emanuelsson R, Strømme M, Sjödin M. Tetraphenylporphyrin electrocatalysts for the hydrogen evolution reaction: applicability of molecular volcano plots to experimental operating conditions. Dalton Trans 2023; 52:10348-10362. [PMID: 37462421 DOI: 10.1039/d3dt01250f] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/02/2023]
Abstract
Recent years have seen an increasing interest in molecular electrocatalysts for the hydrogen evolution reaction (HER). Efficient hydrogen evolution would play an important role in a sustainable fuel economy, and molecular systems could serve as highly specific and tunable alternatives to traditional noble metal surface catalysts. However, molecular catalysts are currently mostly used in homogeneous setups, where quantitative evaluation of catalytic activity is non-standardized and cumbersome, in particular for multistep, multielectron processes. The molecular design community would therefore be well served by a straightforward model for prediction and comparison of the efficiency of molecular catalysts. Recent developments in this area include attempts at applying the Sabatier principle and the volcano plot concept - popular tools for comparing metal surface catalysts - to molecular catalysis. In this work, we evaluate the predictive power of these tools in the context of experimental operating conditions, by applying them to a series of tetraphenylporphyrins employed as molecular electrocatalysts of the HER. We show that the binding energy of H and the redox chemistry of the porphyrins depend solely on the electron withdrawing ability of the central metal ion, and that the thermodynamics of the catalytic cycle follow a simple linear free energy relation. We also find that the catalytic efficiency of the porphyrins is almost exclusively determined by reaction kinetics and therefore cannot be explained by thermodynamics alone. We conclude that the Sabatier principle, linear free energy relations and molecular volcano plots are insufficient tools for predicting and comparing activity of molecular catalysts, and that experimentally useful information of catalytic performance can still only be obtained through detailed knowledge of the catalytic pathway for each individual system.
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Affiliation(s)
- Felicia Zaar
- Department of Materials Science and Engineering, Division of Nanotechnology and Functional Materials, Uppsala University, Box 35, SE-751 03 Uppsala, Sweden.
| | - C Moyses Araujo
- Materials Theory Division, Department of Physics and Astronomy, Ångström Laboratory, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden
- Department of Engineering and Physics, Karlstad University, 651 88 Karlstad, Sweden
| | - Rikard Emanuelsson
- Department of Chemistry - BMC, Uppsala University, Box 576, SE-751 23 Uppsala, Sweden
| | - Maria Strømme
- Department of Materials Science and Engineering, Division of Nanotechnology and Functional Materials, Uppsala University, Box 35, SE-751 03 Uppsala, Sweden.
| | - Martin Sjödin
- Department of Materials Science and Engineering, Division of Nanotechnology and Functional Materials, Uppsala University, Box 35, SE-751 03 Uppsala, Sweden.
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Carvalho R, Marchiori CFN, Brandell D, Araujo CM. Understanding the lithiation limits of high-capacity organic battery anodes by atomic charge derivative analysis. J Chem Phys 2022; 157:181101. [DOI: 10.1063/5.0119904] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The superlithiation of organic anodes is a promising approach for developing the next generation of sustainable Li-ion batteries with high capacity. However, the lack of fundamental understanding hinders its faster development. Here, a systematic study of the lithiation processes in a set of dicarboxylate-based materials is carried out within the density functional theory formalism. It is demonstrated that a combined analysis of the Li insertion reaction thermodynamics and the conjugated-moiety charge derivative is able of establishing the experimentally observed maximum storage limits allowing also the assessment of the structure-function relationships.
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Affiliation(s)
| | | | - Daniel Brandell
- Departmnet of Chemistry - Ångström, Uppsala University, Sweden
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Chen Q, Han YH, Franco LR, Marchiori CFN, Genene Z, Araujo CM, Lee JW, Phan TNL, Wu J, Yu D, Kim DJ, Kim TS, Hou L, Kim BJ, Wang E. Effects of Flexible Conjugation-Break Spacers of Non-Conjugated Polymer Acceptors on Photovoltaic and Mechanical Properties of All-Polymer Solar Cells. Nanomicro Lett 2022; 14:164. [PMID: 35962874 PMCID: PMC9375791 DOI: 10.1007/s40820-022-00884-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 05/24/2022] [Indexed: 06/15/2023]
Abstract
HIGHLIGHTS A series of non-conjugated acceptor polymers with flexible conjugation-break spacers (FCBSs) of different lengths were synthesized. The effect of FCBSs length on solubility of the acceptor polymers, and their photovoltaic and mechanical properties in all-polymer solar cells were explored. This work provides useful guidelines for the design of semiconducting polymers by introducing FCBS with proper length, which can giantly improved properties that are not possible to be achieved by the state-of-the-art fully conjugated polymers. ABSTRACT All-polymer solar cells (all-PSCs) possess attractive merits including superior thermal stability and mechanical flexibility for large-area roll-to-roll processing. Introducing flexible conjugation-break spacers (FCBSs) into backbones of polymer donor (PD) or polymer acceptor (PA) has been demonstrated as an efficient approach to enhance both the photovoltaic (PV) and mechanical properties of the all-PSCs. However, length dependency of FCBS on certain all-PSC related properties has not been systematically explored. In this regard, we report a series of new non-conjugated PAs by incorporating FCBS with various lengths (2, 4, and 8 carbon atoms in thioalkyl segments). Unlike common studies on so-called side-chain engineering, where longer side chains would lead to better solubility of those resulting polymers, in this work, we observe that the solubilities and the resulting photovoltaic/mechanical properties are optimized by a proper FCBS length (i.e., C2) in PA named PYTS-C2. Its all-PSC achieves a high efficiency of 11.37%, and excellent mechanical robustness with a crack onset strain of 12.39%, significantly superior to those of the other PAs. These results firstly demonstrate the effects of FCBS lengths on the PV performance and mechanical properties of the all-PSCs, providing an effective strategy to fine-tune the structures of PAs for highly efficient and mechanically robust PSCs. [Image: see text] SUPPLEMENTARY INFORMATION The online version contains supplementary material available at 10.1007/s40820-022-00884-8.
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Affiliation(s)
- Qiaonan Chen
- Siyuan Laboratory, Guangzhou Key Laboratory of Vacuum Coating Technologies and New Energy Materials, Department of Physics, Jinan University, Guangzhou, 510632, People's Republic of China
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412 96, Göteborg, Sweden
| | - Yung Hee Han
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
| | - Leandro R Franco
- Department of Engineering and Physics, Karlstad University, 65188, Karlstad, Sweden
| | - Cleber F N Marchiori
- Department of Engineering and Physics, Karlstad University, 65188, Karlstad, Sweden
| | - Zewdneh Genene
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412 96, Göteborg, Sweden
| | - C Moyses Araujo
- Department of Engineering and Physics, Karlstad University, 65188, Karlstad, Sweden
- Materials Theory Division, Department of Physics and Astronomy, Uppsala University, 75120, Uppsala, Sweden
| | - Jin-Woo Lee
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
| | - Tan Ngoc-Lan Phan
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
| | - Jingnan Wu
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412 96, Göteborg, Sweden
- Department of Chemistry and Bioscience, Aalborg University, 9220, Aalborg, Denmark
| | - Donghong Yu
- Department of Chemistry and Bioscience, Aalborg University, 9220, Aalborg, Denmark
- Sino-Danish Center for Education and Research, 8000, Aarhus, Denmark
| | - Dong Jun Kim
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
| | - Taek-Soo Kim
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
| | - Lintao Hou
- Siyuan Laboratory, Guangzhou Key Laboratory of Vacuum Coating Technologies and New Energy Materials, Department of Physics, Jinan University, Guangzhou, 510632, People's Republic of China.
| | - Bumjoon J Kim
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea.
| | - Ergang Wang
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412 96, Göteborg, Sweden.
- School of Materials Science and Engineering, Zhengzhou University, Zhengzhou, 450001, People's Republic of China.
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9
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Carvalho RP, Alhanash M, Marchiori CFN, Brandell D, Araujo CM. Exploring Metastable Phases During Lithiation of Organic Battery Electrode Materials. ChemSusChem 2022; 15:e202200354. [PMID: 35389531 PMCID: PMC9321076 DOI: 10.1002/cssc.202200354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 04/04/2022] [Indexed: 06/14/2023]
Abstract
In this work, the Li-ion insertion mechanism in organic electrode materials is investigated through the lens of atomic-scale models based on first-principles theory. Starting with a structural analysis, the interplay of density functional theory with evolutionary and potential-mapping algorithms is used to resolve the crystal structure of the different (de)lithiated phases. These methods elucidate different lithiation reaction pathways and help to explore the formation of metastable phases and predict one- or multi-electron reactions, which are still poorly understood for organic intercalation electrodes. The cathode material dilithium 2,5-oxyterephthalate (operating at 2.6 V vs. Li/Li+) is investigated in depth as a case study, owing to its rich redox chemistry. When compared with recent experimental results, it is demonstrated that metastable phases with peculiar ring-ring molecular interactions are more likely to be controlling the redox reactions thermodynamics and consequently the battery voltage.
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Affiliation(s)
- Rodrigo P. Carvalho
- Materials Theory DivisionDepartment of Physics and AstronomyUppsala UniversityBox 51675120UppsalaSweden
- Department of Chemistry – Ångström LaboratoryUppsala UniversityBox 53875121UppsalaSweden
| | - Mirna Alhanash
- Materials Theory DivisionDepartment of Physics and AstronomyUppsala UniversityBox 51675120UppsalaSweden
- Materials Physics DivisionDepartment of PhysicsChalmers University of Technology41296GöteborgSweden
| | | | - Daniel Brandell
- Department of Chemistry – Ångström LaboratoryUppsala UniversityBox 53875121UppsalaSweden
| | - C. Moyses Araujo
- Materials Theory DivisionDepartment of Physics and AstronomyUppsala UniversityBox 51675120UppsalaSweden
- Department of Engineering and PhysicsKarlstad University65188KarlstadSweden
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Franco LR, Toledo KCF, Matias TA, Benavides PA, Cezar HM, Araujo CM, Coutinho K, Araki K. Unraveling the acid-base characterization and solvent effects on the structural and electronic properties of a bis-bidentate bridging ligand. Phys Chem Chem Phys 2022; 24:10222-10240. [PMID: 35420602 DOI: 10.1039/d1cp03912a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Understanding the interactions and the solvent effects on the distribution of several species in equilibrium and how it can influence the 1H-NMR properties, spectroscopy (UV-vis absorption), and the acid-base equilibria can be especially challenging. This is the case of a bis-bidentate bridging ligand bis(2-pyridyl)-benzo-bis(imidazole), where the two pyridyl and four imidazolyl nitrogen atoms can be protonated in different ways, depending on the solvent, generating many isomeric/tautomeric species. Herein, we report a combined theoretical-experimental approach based on a sequential quantum mechanics/molecular mechanics procedure that was successfully applied to describe in detail the acid-base characterization and its effects on the electronic properties of such a molecule in solution. The calculated free-energies allowed the identification of the main species present in solution as a function of the solvent polarity, and its effects on the magnetic shielding of protons (1H-NMR chemical shifts), the UV-vis absorption spectra, and the acid-base equilibrium constants (pKas) in aqueous solution. Three acid-base equilibrium constants were experimentally/theoretically determined (pKa1 = 1.3/1.2, pKa2 = 2.1/2.2 and pKa5 = 10.1/11.3) involving mono-deprotonated and mono-protonated cis and trans species. Interestingly, other processes with pKa3 = 3.7 and pKa4 = 6.0 were also experimentally determined and assigned to the protonation and deprotonation of dimeric species. The dimerization of the most stable neutral species was investigated by Monte Carlo simulations and its electronic effects were considered for the elucidation of the UV-vis absorption bands, revealing transitions mainly with the charge-transfer characteristic and involving both the monomeric species and the dimeric species. The good matching of the theoretical and experimental results provides an atomistic insight into the solvent effects on the electronic properties of this bis-bidentate bridging ligand.
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Affiliation(s)
- Leandro Rezende Franco
- Instituto de Física, Universidade de São Paulo, Cidade Universitária, 05508-090 São Paulo, SP, Brazil. .,Department of Engineering and Physics, Karlstad University, 65188 Karlstad, Sweden
| | | | - Tiago Araujo Matias
- Instituto de Química, Universidade de São Paulo, Av. Lineu Prestes 748, Butantã, 05508-000 São Paulo, SP, Brazil.
| | - Paola Andrea Benavides
- Instituto de Química, Universidade de São Paulo, Av. Lineu Prestes 748, Butantã, 05508-000 São Paulo, SP, Brazil.
| | - Henrique Musseli Cezar
- Instituto de Física, Universidade de São Paulo, Cidade Universitária, 05508-090 São Paulo, SP, Brazil.
| | - C Moyses Araujo
- Department of Engineering and Physics, Karlstad University, 65188 Karlstad, Sweden.,Materials Theory Division, Department of Physics and Astronomy, Ångström Laboratory, Uppsala University, 75120 Uppsala, Sweden
| | - Kaline Coutinho
- Instituto de Física, Universidade de São Paulo, Cidade Universitária, 05508-090 São Paulo, SP, Brazil.
| | - Koiti Araki
- Instituto de Química, Universidade de São Paulo, Av. Lineu Prestes 748, Butantã, 05508-000 São Paulo, SP, Brazil.
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11
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Axelsson M, Marchiori CFN, Huang P, Araujo CM, Tian H. Small Organic Molecule Based on Benzothiadiazole for Electrocatalytic Hydrogen Production. J Am Chem Soc 2021; 143:21229-21233. [PMID: 34855386 PMCID: PMC8704194 DOI: 10.1021/jacs.1c10600] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
A small organic molecule
2,1,3-benzothiadiazole-4, 7-dicarbonitrile
(BTDN) is assessed for electrocatalytic hydrogen evolution on glassy
carbon electrode and shows a hydrogen production Faradaic efficiency
of 82% in the presence of salicylic acid. The key catalytic intermediates
of reduced species BTDN–• and protonated
intermediates are characterized or hypothesized by using various spectroscopic
methods and density functional theory (DFT)-based calculations. With
the experimental and theoretical results, a catalytic mechanism of
BTDN for electrocatalytic H2 evolution is proposed.
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Affiliation(s)
- Martin Axelsson
- Department of Chemistry-Ångström Laboratory, Uppsala University, Uppsala SE 751 20, Sweden
| | - Cleber F N Marchiori
- Department of Engineering and Physics, Karlstad University, Karlstad 65188, Sweden
| | - Ping Huang
- Department of Chemistry-Ångström Laboratory, Uppsala University, Uppsala SE 751 20, Sweden
| | - C Moyses Araujo
- Department of Engineering and Physics, Karlstad University, Karlstad 65188, Sweden.,Department of Physics and Astronomy, Ångström Laboratory, Uppsala University, Uppsala 751 20, Sweden
| | - Haining Tian
- Department of Chemistry-Ångström Laboratory, Uppsala University, Uppsala SE 751 20, Sweden
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12
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Damas GB, Costa LT, Ahuja R, Araujo CM. Understanding carbon dioxide capture on metal-organic frameworks from first-principles theory: The case of MIL-53(X), with X = Fe 3+, Al 3+, and Cu 2. J Chem Phys 2021; 155:024701. [PMID: 34266252 DOI: 10.1063/5.0054874] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Metal-organic frameworks (MOFs) constitute a class of three-dimensional porous materials that have shown applicability for carbon dioxide capture at low pressures, which is particularly advantageous in dealing with the well-known environmental problem related to the carbon dioxide emissions into the atmosphere. In this work, the effect of changing the metallic center in the inorganic counterpart of MIL-53 (X), where X = Fe3+, Al3+, and Cu2+, has been assessed over the ability of the porous material to adsorb carbon dioxide by means of first-principles theory. In general, the non-spin polarized computational method has led to adsorption energies in fair agreement with the experimental outcomes, where the carbon dioxide stabilizes at the pore center through long-range interactions via oxygen atoms with the axial hydroxyl groups in the inorganic counterpart. However, spin-polarization effects in connection with the Hubbard corrections, on Fe 3d and Cu 3d states, were needed to properly describe the metal orbital occupancy in the open-shell systems (Fe- and Cu-based MOFs). This methodology gave rise to a coherent high-spin configuration, with five unpaired electrons, for Fe atoms leading to a better agreement with the experimental results. Within the GGA+U level of theory, the binding energy for the Cu-based MOF is found to be Eb = -35.85 kJ/mol, which is within the desirable values for gas capture applications. Moreover, it has been verified that the adsorption energetics is dominated by the gas-framework and internal weak interactions.
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Affiliation(s)
- Giane B Damas
- Materials Theory Division, Department of Physics and Astronomy, Uppsala University, 75120 Uppsala, Sweden
| | - Luciano T Costa
- MolMod-CS- Department of Physical-Chemistry, Campus Valonguinho, Institute of Chemistry, Fluminense Federal University, Niterói, Rio de Janeiro, Brazil
| | - Rajeev Ahuja
- Materials Theory Division, Department of Physics and Astronomy, Uppsala University, 75120 Uppsala, Sweden
| | - C Moyses Araujo
- Materials Theory Division, Department of Physics and Astronomy, Uppsala University, 75120 Uppsala, Sweden
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13
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Sousa LAP, Campos APP, Araujo CM, Moreira IGS, Santos G, Costa JM, Vasconcellos JAC, Leal S, Souza AC, Ribeiro ALP. Health education: the effects of an educational program on the health of hypertensive patients with low educational level. Eur J Prev Cardiol 2021. [DOI: 10.1093/eurjpc/zwab061.151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Abstract
Funding Acknowledgements
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): FAPEMIG
Introduction
Health education is one of the most complete practices for supporting of patients with chronic diseases such as hypertension. It is important, however, to investigate which strategies would be more assertive in this process, depending on the objective and profile of the patient. Objective: The aim of this study was to evaluate the effect of an interactive educational program on the health of hypertensive patients with low educational level in a Basic Health Unit in Brazil. Methods: This is an almost experimental study, with a multidisciplinary approach, with 6 months of duration. Interactive workshops were held where topics related to hypertension, such as: pathophysiology, complications, drug and non-drug therapeutic approach and lifestyle change. It is important to emphasize that the work used interactive and playful sessions, such as games, videos and group dynamics. The sample consisted of 35 hypertensive individuals submitted to blood pressure (systolic = SBP and diastolic = DBP) measurement, quality of life (Minichal), adherence to treatment (Martín-Bayarre-Grau), level of knowledge of the disease, physical activity (IPAQ) and anthropometric study evaluation. In addition, for analysis of the data, the sample was divided into two subgroups, according to the participation in the activities: adhered (n = 11) or not adhered (n = 24). Initially, descriptive statistics were used to present the study variables. Subsequently, the WILCOXON test was used to compare before and after and MANN-WHITNEY to compare the two groups, p = 0.05 was considered significant. Results: No significant difference was found relating the initial data in the two subgroups. After the educational program, a significant reduction was observed in relation to the SBP values: 9.8 mmHg in the adherent subgroup. On the other hand, there was increased 0.7 mmHg among non-adherents. The other evaluations did not change. It should be emphasized that the studied population demonstrated a satisfactory level of knowledge of the pathology and the therapeutic process necessary since the initial evaluation in both groups. Such finding, however, was not related to adherence to treatment. Conclusion: the findings suggest that an adapted educational approach could help to control blood pressure levels of hypertensive patients with low educational level. In addition, it was observed that knowledge does not seem to be associated with action, and it is necessary to develop strategies that can increase adherence to therapeutic interventions.
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Affiliation(s)
- LAP Sousa
- Hospital das Clínicas da UFMG, Belo Horizonte, Brazil
| | - APP Campos
- Centro Universitário Newton Paiva, Belo Horizonte, Brazil
| | - CM Araujo
- Centro Universitário Newton Paiva, Belo Horizonte, Brazil
| | - IGS Moreira
- Centro Universitário Newton Paiva, Belo Horizonte, Brazil
| | - G Santos
- Centro Universitário Newton Paiva, Belo Horizonte, Brazil
| | - JM Costa
- Hospital das Clínicas da UFMG, Belo Horizonte, Brazil
| | | | - S Leal
- Centro Universitário Newton Paiva, Belo Horizonte, Brazil
| | - AC Souza
- Centro Universitário Newton Paiva, Belo Horizonte, Brazil
| | - ALP Ribeiro
- Hospital das Clínicas da UFMG, Belo Horizonte, Brazil
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14
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de Araujo LO, Neto AL, Scalon L, Rodrigues PC, Floriano JB, Araujo CM, Marchiori CF, Barreto RC. A new CBD-CC-E spectral similarity scale for optimizing computer-simulated UV–vis spectra. COMPUT THEOR CHEM 2021. [DOI: 10.1016/j.comptc.2020.113116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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15
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Carvalho RP, Marchiori CFN, Brandell D, Araujo CM. Tuning the Electrochemical Properties of Organic Battery Cathode Materials: Insights from Evolutionary Algorithm DFT Calculations. ChemSusChem 2020; 13:2402-2409. [PMID: 32061037 PMCID: PMC7318659 DOI: 10.1002/cssc.201903450] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 02/14/2020] [Indexed: 06/10/2023]
Abstract
Several forms of organic materials have arisen as promising candidates for future active electrode materials for Li-ion and post-Li-ion batteries, owing to a series of key features that encompasses sustainability, accessibility, and tunable electrochemical properties by molecular modifications. In this context, a series of organic electrode materials (OEMs) are investigated to further understand their thermodynamic and electronic properties. Through an evolutionary algorithm approach combined with first-principles calculations, the crystal structure of lithiated and delithiated phases of these OEMs and their respective NO2 -substituted analogues are predicted. This framework allows a first assessment of their electrochemical and electronic properties and further understanding on the effects of the nitro group in the substituted compounds. NO2 is found to strongly affect structural and thermodynamic aspects during the electrochemical reaction with the reducing equivalents (Li+ +e- ), changing the OEM's character from a low-potential anode to a high-potential cathode by creating a localization of the additional electrons, thus resulting in a better-defined redox-active center and leading to a shift in the potential from 0.92 V to 2.66 V vs. Li/Li+ .
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Affiliation(s)
- Rodrigo P. Carvalho
- Materials Theory DivisionDepartment of Physics and AstronomyÅngström LaboratoryUppsala UniversityBox 51675120UppsalaSweden
| | | | - Daniel Brandell
- Department of Chemistry, Ångström LaboratoryUppsala UniversityBox 53875121UppsalaSweden
| | - C. Moyses Araujo
- Materials Theory DivisionDepartment of Physics and AstronomyÅngström LaboratoryUppsala UniversityBox 51675120UppsalaSweden
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16
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Ebadi M, Eriksson T, Mandal P, Costa LT, Araujo CM, Mindemark J, Brandell D. Restricted Ion Transport by Plasticizing Side Chains in Polycarbonate-Based Solid Electrolytes. Macromolecules 2020; 53:764-774. [PMID: 32089567 PMCID: PMC7032846 DOI: 10.1021/acs.macromol.9b01912] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 12/23/2019] [Indexed: 11/29/2022]
Abstract
Increasing the ionic conductivity has for decades been an overriding goal in the development of solid polymer electrolytes. According to fundamental theories on ion transport mechanisms in polymers, the ionic conductivity is strongly correlated to free volume and segmental mobility of the polymer for the conventional transport processes. Therefore, incorporating plasticizing side chains onto the main chain of the polymer host often appears as a clear-cut strategy to improve the ionic conductivity of the system through lowering of the glass transition temperature (T g). This intended correlation between T g and ionic conductivity is, however, not consistently observed in practice. The aim of this study is therefore to elucidate this interplay between segmental mobility and polymer structure in polymer electrolyte systems comprising plasticizing side chains. To this end, we utilize the synthetic versatility of the ion-conductive poly(trimethylene carbonate) (PTMC) platform. Two types of host polymers with side chains added to a PTMC backbone are employed, and the resulting electrolytes are investigated together with the side chain-free analogue both by experiment and with molecular dynamics (MD) simulations. The results show that while added side chains do indeed lead to a lower T g, the total ionic conductivity is highest in the host matrix without side chains. It was seen in the MD simulations that while side chains promote ionic mobility associated with the polymer chain, the more efficient interchain hopping transport mechanism occurs with a higher probability in the system without side chains. This is connected to a significantly higher solvation site diversity for the Li+ ions in the side-chain-free system, providing better conduction paths. These results strongly indicate that the side chains in fact restrict the mobility of the Li+ ions in the polymer hosts.
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Affiliation(s)
- Mahsa Ebadi
- Department
of Chemistry − Ångström Laboratory, Uppsala University, Box 538, SE-751 21 Uppsala, Sweden
| | - Therese Eriksson
- Department
of Chemistry − Ångström Laboratory, Uppsala University, Box 538, SE-751 21 Uppsala, Sweden
| | - Prithwiraj Mandal
- Department
of Chemistry − Ångström Laboratory, Uppsala University, Box 538, SE-751 21 Uppsala, Sweden
| | - Luciano T. Costa
- Instituto
de Química−Departamento de Físico-química, Universidade Federal Fluminense, Outeiro de São João Batista s/n, CEP 24020-150 Niterói, RJ, Brazil
| | - C. Moyses Araujo
- Materials
Theory Division, Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden
| | - Jonas Mindemark
- Department
of Chemistry − Ångström Laboratory, Uppsala University, Box 538, SE-751 21 Uppsala, Sweden
| | - Daniel Brandell
- Department
of Chemistry − Ångström Laboratory, Uppsala University, Box 538, SE-751 21 Uppsala, Sweden
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17
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Silva JL, Unger I, Matias TA, Franco LR, Damas G, Costa LT, Toledo KCF, Rocha TCR, de Brito AN, Saak CM, Coutinho K, Araki K, Björneholm O, Brena B, Araujo CM. X-ray Photoelectron Fingerprints of High-Valence Ruthenium-Oxo Complexes along the Oxidation Reaction Pathway in an Aqueous Environment. J Phys Chem Lett 2019; 10:7636-7643. [PMID: 31747290 DOI: 10.1021/acs.jpclett.9b02756] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Recent advances in operando-synchrotron-based X-ray techniques are making it possible to address fundamental questions related to complex proton-coupled electron transfer reactions, for instance, the electrocatalytic water splitting process. However, it is still a grand challenge to assess the ability of the different techniques to characterize the relevant intermediates, with minimal interference on the reaction mechanism. To this end, we have developed a novel methodology employing X-ray photoelectron spectroscopy (XPS) in connection with the liquid-jet approach to probe the electrochemical properties of a model electrocatalyst, [RuII(bpy)2(py)(OH2)]2+, in an aqueous environment. There is a unique fingerprint of the extremely important higher-valence ruthenium-oxo species in the XPS spectra along the oxidation reaction pathway. Furthermore, a sequential method combining quantum mechanics and molecular mechanics is used to illuminate the underlying physical chemistry of such systems. This study provides the basis for the future development of in-operando XPS techniques for water oxidation reactions.
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Affiliation(s)
- Jose Luis Silva
- Materials Theory Division, Department of Physics and Astronomy , Uppsala University , Box 516, 75120 Uppsala , Sweden
| | - Isaak Unger
- Molecular and Condensed Matter Physics Division, Department of Physics and Astronomy , Uppsala University , Box 516, 75120 Uppsala , Sweden
| | - Tiago Araujo Matias
- Department of Fundamental Chemistry, Institute of Chemistry , University of São Paulo , Av. Lineu Prestes 748, Cidade Universitária, Butanta , Sao Paulo , SP 05508-000 , Brazil
| | - Leandro Rezende Franco
- Instituto de Física , Universidade de São Paulo , Cidade Universitária , 05508-090 São Paulo , SP , Brazil
| | - Giane Damas
- Materials Theory Division, Department of Physics and Astronomy , Uppsala University , Box 516, 75120 Uppsala , Sweden
| | - Luciano T Costa
- Instituto de Química, Departamento de Físico-química , Universidade Federal Fluminense , Outeiro de São João Batista s/n , CEP, 24020-150 Niterói , RJ , Brazil
| | - Kalil C F Toledo
- Department of Fundamental Chemistry, Institute of Chemistry , University of São Paulo , Av. Lineu Prestes 748, Cidade Universitária, Butanta , Sao Paulo , SP 05508-000 , Brazil
| | - Tulio C R Rocha
- Brazilian Synchrotron Light Laboratory (LNLS) , Brazilian Center for Research on Energy and Materials (CNPEM) , P.O. Box 6192, 13083-970 Campinas , SP , Brazil
| | - Arnaldo Naves de Brito
- Institute of Physics "Gleb Wataghin" , University of Campinas , 13083-859 Campinas , SP , Brazil
| | - Clara-Magdalena Saak
- Molecular and Condensed Matter Physics Division, Department of Physics and Astronomy , Uppsala University , Box 516, 75120 Uppsala , Sweden
| | - Kaline Coutinho
- Instituto de Física , Universidade de São Paulo , Cidade Universitária , 05508-090 São Paulo , SP , Brazil
| | - Koiti Araki
- Department of Fundamental Chemistry, Institute of Chemistry , University of São Paulo , Av. Lineu Prestes 748, Cidade Universitária, Butanta , Sao Paulo , SP 05508-000 , Brazil
| | - Olle Björneholm
- Molecular and Condensed Matter Physics Division, Department of Physics and Astronomy , Uppsala University , Box 516, 75120 Uppsala , Sweden
| | - Barbara Brena
- Materials Theory Division, Department of Physics and Astronomy , Uppsala University , Box 516, 75120 Uppsala , Sweden
| | - C Moyses Araujo
- Materials Theory Division, Department of Physics and Astronomy , Uppsala University , Box 516, 75120 Uppsala , Sweden
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18
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Lanzilotto V, Silva JL, Zhang T, Stredansky M, Grazioli C, Simonov K, Giangrisostomi E, Ovsyannikov R, De Simone M, Coreno M, Araujo CM, Brena B, Puglia C. Spectroscopic Fingerprints of Intermolecular H-Bonding Interactions in Carbon Nitride Model Compounds. Chemistry 2018; 24:14198-14206. [PMID: 30009392 DOI: 10.1002/chem.201802435] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 07/11/2018] [Indexed: 11/10/2022]
Abstract
The effect of intermolecular H-bonding interactions on the local electronic structure of N-containing functional groups (amino group and pyridine-like N) that are characteristic of polymeric carbon nitride materials p-CN(H), a new class of metal-free organophotocatalysts, was investigated. Specifically, the melamine molecule, a building block of p-CN(H), was characterized by X-ray photoelectron (XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The molecule was studied as a noninteracting system in the gas phase and in the solid state within a H-bonded network. With the support of DFT simulations of the spectra, it was found that the H-bonds mainly affect the N 1s level of the amino group, leaving the N 1s level of the pyridine-like N mostly unperturbed. This is responsible for a reduction of the chemical shift between the two XPS N 1s levels relative to free melamine. Consequently, N K-edge NEXAFS resonances involving the amino N 1s level also shift to lower photon energies. Moreover, the solid-state absorption spectra showed significant modification/quenching of resonances related to transitions from the amino N 1s level to σ* orbitals involving the NH2 termini.
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Affiliation(s)
- Valeria Lanzilotto
- Department of Physics and Astronomy, Uppsala University, P.O. BOX 516, 751 20, Uppsala, Sweden
| | - J Luis Silva
- Department of Physics and Astronomy, Uppsala University, P.O. BOX 516, 751 20, Uppsala, Sweden
| | - Teng Zhang
- Department of Physics and Astronomy, Uppsala University, P.O. BOX 516, 751 20, Uppsala, Sweden
| | - Matuš Stredansky
- Department of Physics, University of Trieste, Via A. Valerio 2, 34127, Trieste, Italy.,IOM-CNR, Istituto Officina dei Materiali, Laboratorio TASC, Basovizza SS-14, Km 163.5, 34149, Trieste, Italy
| | - Cesare Grazioli
- ISM-CNR, Istituto di Struttura della Materia, LD2 Unit, Basovizza SS-14, Km 163.5, 34149, Trieste, Italy
| | - Konstantin Simonov
- Department of Physics and Astronomy, Uppsala University, P.O. BOX 516, 751 20, Uppsala, Sweden
| | - Erika Giangrisostomi
- Institute Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin GmbH, Albert-Einstein-Strasse 15, 12489, Berlin, Germany
| | - Ruslan Ovsyannikov
- Institute Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin GmbH, Albert-Einstein-Strasse 15, 12489, Berlin, Germany
| | - Monica De Simone
- IOM-CNR, Istituto Officina dei Materiali, Laboratorio TASC, Basovizza SS-14, Km 163.5, 34149, Trieste, Italy
| | - Marcello Coreno
- ISM-CNR, Istituto di Struttura della Materia, LD2 Unit, Basovizza SS-14, Km 163.5, 34149, Trieste, Italy
| | - C Moyses Araujo
- Department of Physics and Astronomy, Uppsala University, P.O. BOX 516, 751 20, Uppsala, Sweden
| | - Barbara Brena
- Department of Physics and Astronomy, Uppsala University, P.O. BOX 516, 751 20, Uppsala, Sweden
| | - Carla Puglia
- Department of Physics and Astronomy, Uppsala University, P.O. BOX 516, 751 20, Uppsala, Sweden
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19
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Espinosa-García WF, Pérez-Walton S, Osorio-Guillén JM, Moyses Araujo C. The electronic and optical properties of the sulvanite compounds: a many-body perturbation and time-dependent density functional theory study. J Phys Condens Matter 2018; 30:035502. [PMID: 29182517 DOI: 10.1088/1361-648x/aa9deb] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We have studied, by means of first-principles calculations, the electronic and optical properties of the sulvanite family: Cu3MX4 (M = V, Nb, Ta and X = S, Se), which, due to its broad range of gaps and chemical stability, have emerged as promising materials for technological applications such as photovoltaics and transparent conductivity. To address the reliability of those properties we have used semi-local and hybrid functionals (PBEsol, HSE06), many-body perturbation theory (G0W0 approximation and Bethe-Salpeter equation), and time-dependent density functional theory (revised bootstrap kernel) to calculate the quasi-particle dispersion relation, band gaps, the imaginary part of the macroscopic dielectric function and the absorption coefficient. The calculated valence band maximum and the conduction band minimum are located at the R and X-points, respectively. The calculated gaps using PBEsol are between 0.81 and 1.88 eV, with HSE06 into 1.73 and 2.94 eV, whereas the G0W0 values fall into the 1.91-3.19 eV range. The calculated dielectric functions and absorption coefficients show that all these compounds present continuous excitonic features when the Bethe-Salpeter equation is used. Contrarily, the revised bootstrap kernel is incapable of describing the excitonic spectra. The calculated optical spectra show that Cu3VS4 and Cu3MSe4 have good absorption in the visible, whereas Cu3NbS4 and Cu3TaS4 have it on the near ultraviolet.
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Affiliation(s)
- W F Espinosa-García
- Facultad de Ingenierías, Grupo de Investigación en Modelamiento y Simulación Computacional, Universidad de San Buenaventura-Medellín, Carrera 56C No 51-110, Medellín, Colombia. Instituto de Física, Universidad de Antioquia UdeA, Calle 70 No 52-21, Medellín, Colombia
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20
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Triana CA, Araujo CM, Ahuja R, Niklasson GA, Edvinsson T. Disentangling the intricate atomic short-range order and electronic properties in amorphous transition metal oxides. Sci Rep 2017; 7:2044. [PMID: 28515466 PMCID: PMC5435740 DOI: 10.1038/s41598-017-01151-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 03/21/2017] [Indexed: 12/03/2022] Open
Abstract
Solid state materials with crystalline order have been well-known and characterized for almost a century while the description of disordered materials still bears significant challenges. Among these are the atomic short-range order and electronic properties of amorphous transition metal oxides [aTMOs], that have emerged as novel multifunctional materials due to their optical switching properties and high-capacity to intercalate alkali metal ions at low voltages. For decades, research on aTMOs has dealt with technological optimization. However, it remains challenging to unveil their intricate atomic short-range order. Currently, no systematic and broadly applicable methods exist to assess atomic-size structure, and since electronic localization is structure-dependent, still there are not well-established optical and electronic mechanisms for modelling the properties of aTMOs. We present state-of-the-art systematic procedures involving theory and experiment in a self-consistent computational framework to unveil the atomic short-range order and its role for the electronic properties. The scheme is applied to amorphous tungsten trioxide aWO3, which is the most studied electrochromic aTMO in spite of its unidentified atomic-size structure. Our approach provides a one-to-one matching of experimental data and corresponding model structure from which electronic properties can be directly calculated in agreement with the electronic transitions observed in the XANES spectra.
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Affiliation(s)
- C A Triana
- Division of Solid State Physics, Department of Engineering Sciences, The Ångström Laboratory, Uppsala University, P.O. Box 534, SE-751 21, Uppsala, Sweden.
| | - C Moyses Araujo
- Materials Theory Division, Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-75120, Uppsala, Sweden
| | - R Ahuja
- Materials Theory Division, Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-75120, Uppsala, Sweden
| | - G A Niklasson
- Division of Solid State Physics, Department of Engineering Sciences, The Ångström Laboratory, Uppsala University, P.O. Box 534, SE-751 21, Uppsala, Sweden
| | - T Edvinsson
- Division of Solid State Physics, Department of Engineering Sciences, The Ångström Laboratory, Uppsala University, P.O. Box 534, SE-751 21, Uppsala, Sweden
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Espinosa-García WF, Osorio-Guillén JM, Araujo CM. Dimension-dependent band alignment and excitonic effects in graphitic carbon nitride: a many-body perturbation and time-dependent density functional theory study. RSC Adv 2017. [DOI: 10.1039/c7ra07134e] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
First-principles many-body theory and time-dependent density functional theory were used to study the dimension effects on the band alignment and optical properties of s-triazine and graphitic C3N4.
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Affiliation(s)
- W. F. Espinosa-García
- Universidad de San Buenaventura-Medellín
- Facultad de Ingenierías
- Grupo de Investigación en Modelamiento y Simulación Computacional
- Medellín
- Colombia
| | | | - C. Moyses Araujo
- Materials Theory Division
- Department of Physics and Astronomy
- Uppsala University
- Uppsala
- Sweden
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Araujo RB, Banerjee A, Panigrahi P, Yang L, Sjödin M, Strømme M, Araujo CM, Ahuja R. Assessing the electrochemical properties of polypyridine and polythiophene for prospective applications in sustainable organic batteries. Phys Chem Chem Phys 2017; 19:3307-3314. [DOI: 10.1039/c6cp07435a] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this work, a theoretical protocol has been developed to calculate redox potentials in solution within the framework of the density functional theory and using continuous solvation model.
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Affiliation(s)
- Rafael B. Araujo
- Materials Theory Division
- Department of Physics and Astronomy
- Uppsala University
- Uppsala
- Sweden
| | - Amitava Banerjee
- Materials Theory Division
- Department of Physics and Astronomy
- Uppsala University
- Uppsala
- Sweden
| | - Puspamitra Panigrahi
- Materials Theory Division
- Department of Physics and Astronomy
- Uppsala University
- Uppsala
- Sweden
| | - Li Yang
- Nanotechnology and Functional Materials
- Department of Engineering Sciences
- The Ångström Laboratory
- Uppsala University
- SE-751 21 Uppsala
| | - Martin Sjödin
- Nanotechnology and Functional Materials
- Department of Engineering Sciences
- The Ångström Laboratory
- Uppsala University
- SE-751 21 Uppsala
| | - Maria Strømme
- Nanotechnology and Functional Materials
- Department of Engineering Sciences
- The Ångström Laboratory
- Uppsala University
- SE-751 21 Uppsala
| | - C. Moyses Araujo
- Materials Theory Division
- Department of Physics and Astronomy
- Uppsala University
- Uppsala
- Sweden
| | - Rajeev Ahuja
- Materials Theory Division
- Department of Physics and Astronomy
- Uppsala University
- Uppsala
- Sweden
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Osorio-Guillén JM, Espinosa-García WF, Moyses Araujo C. Assessing photocatalytic power of g-C3N4 for solar fuel production: A first-principles study involving quasi-particle theory and dispersive forces. J Chem Phys 2015; 143:094705. [DOI: 10.1063/1.4929989] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- J. M. Osorio-Guillén
- Instituto de Física, Universidad de Antioquia UdeA, Calle 70 No 52-21, Medellín, Colombia
| | - W. F. Espinosa-García
- Instituto de Física, Universidad de Antioquia UdeA, Calle 70 No 52-21, Medellín, Colombia
- Grupo de Investigación en Modelamiento y Simulación Computacional, Facultad de Ingenierías, Universidad de San Buenaventura Seccional Medellín, Carrera 56C No 51-110, Medellín, Colombia
| | - C. Moyses Araujo
- Materials Theory Division, Department of Physics and Astronomy, Uppsala University, P.O. Box 516, S75120 Uppsala, Sweden
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Panigrahi P, Hussain T, Araujo CM, Ahuja R. Hole induced Jahn Teller distortion ensuing ferromagnetism in Mn-MgO: bulk, surface and one dimensional structures. J Phys Condens Matter 2014; 26:265801. [PMID: 24903474 DOI: 10.1088/0953-8984/26/26/265801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Using density functional theory, we investigate the magnetic properties of Mn doped MgO in its bulk (3D), surface (2D) and one dimensional (1D) structures. At a low dilute limit (1.5 %), the Mn impurity behaves indifferent to its position in 3D but energetically prefers to be on one of the surfaces of 2D and 1D structures. At a higher dilute limit (3.1 %), the Mn impurities stabilizing at MN(d)((3+)) ionic states prefer to be in a close configuration (4.2 Å compared to 5.95 Å) and the antiferromagnetic ordering (AFM) between them is preferred over the ferromagnetic ordering. The n-type extrinsic defects (O vacancy), when introduced to Mn doped MgO structures, also result in similar AFM exchanges as between the Mn impurities. However, the p-type defects (Mg vacancy) in the Mn doped MgO structures result in a reduced magnetic moment for the Mn atoms and bring a significant Jahn Teller (JT)-type of distortion to the eg and t2g degenerate states of MN(d)((3+)) ions. The strong hybridization between distorted Mnd states and O2p states results in a FM exchange coupling between the Mn ions, in all the three mentioned Mn doped MgO structures. As we move from 3D to 2D, to 1D structures, the influence of JT distortion decreases, reflecting a decreasing trend for the strength of the FM exchange coupling between the Mn atoms.
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Affiliation(s)
- Puspamitra Panigrahi
- Condensed Matter Theory Group, Materials Theory Division, Department of Physics and Astronomy, Uppsala University, P.O Box 530, S75121, Uppsala, Sweden
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Panigrahi P, Araujo CM, Hussen T, Ahuja R. Crafting ferromagnetism in Mn-doped MgO surfaces with p-type defects. Sci Technol Adv Mater 2014; 15:035008. [PMID: 27877684 PMCID: PMC5090529 DOI: 10.1088/1468-6996/15/3/035008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2014] [Accepted: 05/13/2014] [Indexed: 05/12/2023]
Abstract
We have employed first-principles calculations based on density functional theory (DFT) to investigate the underlying physics of unusual magnetism in Mn-doped MgO surface. We have studied two distinct scenarios. In the first one, two Mn atoms are substitutionally added to the surface, occupying the Mg sites. Both are stabilized in the Mn[Formula: see text] valence state carrying a local moment of 4.3 [Formula: see text] having a high-spin configuration. The magnetic interaction between the local moments display a very short-ranged characteristic, decaying very quickly with distance, and having antiferromagnetic ordering lower in energy. The energetics analysis also indicates that the Mn ions prefer to stay close to each other with an oxygen atom bridging the local interaction. In the second scenario, we started exploring the effect of native defects on the magnetism by crafting both Mg and O vacancies, which are p- and n-type defects, respectively. It is found that the electrons and holes affect the magnetic interaction between Mn ions in a totally different manner. The n-type defect leads to very similar magnetism, with the AFM configuration being energetically preferred. However, in the presence of Mg vacancy, the situation is quite different. The Mn atoms are further oxidized, giving rise to mixed Mn(d) ionic states. As a consequence, the Mn atoms couple ferromagnetically, when placed in the close configuration, and the obtained electronic structure is coherent with the double-exchange type of magnetic interaction. To guarantee the robustness of our results, we have benchmarked our calculations with three distinct theory levels, namely DFT-GGA, DFT-GGA+U and DFT-hybrid functionals. On the surface, the Mg vacancy displays lower formation energy occurring at higher concentrations. Therefore, our model systems can be the basis to explain a number of controversial results regarding transition metal doped oxides.
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Affiliation(s)
- Puspamitra Panigrahi
- Condensed Matter Theory Group, Materials Theory Division, Department of Physics and Astronomy, Uppsala University, PO Box 530, S75121, Uppsala, Sweden
| | - C Moyses Araujo
- Condensed Matter Theory Group, Materials Theory Division, Department of Physics and Astronomy, Uppsala University, PO Box 530, S75121, Uppsala, Sweden
| | - Tanveer Hussen
- Condensed Matter Theory Group, Materials Theory Division, Department of Physics and Astronomy, Uppsala University, PO Box 530, S75121, Uppsala, Sweden
| | - Rajeev Ahuja
- Condensed Matter Theory Group, Materials Theory Division, Department of Physics and Astronomy, Uppsala University, PO Box 530, S75121, Uppsala, Sweden
- Applied Materials Physics, Departments of Materials and Engineering, Royal Institute of Technology (KTH), S-10044, Stockholm, Sweden
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Abstract
Recent breakthroughs in electrochemical studies have reported aqueous CO2 reduction to formic acid, formaldehyde, and methanol at low overpotentials (-0.58 V versus SCE), with a Pt working electrode in acidic pyridine (Pyr) solutions. We find that CO2 is reduced by H atoms bound to the Pt surface that are transferred as hydrides to CO2 in a proton-coupled hydride transfer (PCHT) mechanism activated by pyridinium (PyrH(+)), CO2 + Pt-H + PyrH(+) + e(-) → Pyr + Pt + HCO2H. The surface-bound H atoms consumed by CO2 reduction is replenished by the one-electron reduction of PyrH(+) through the proton-coupled electron transfer (PCET), PyrH(+) + Pt + e(-) → Pyr + Pt-H. Pyridinium is essential to establish a high concentration of Brønsted acid in contact with CO2 and with the Pt surface, much higher than the concentration of free protons. These findings are particularly relevant to generate fuels with a carbon-neutral footprint.
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Affiliation(s)
- Mehmed Z Ertem
- †Department of Chemistry, Brookhaven National Laboratory, Building 555A, Upton, New York 11973, United States
- ‡Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 08107-06520, United States
| | - Steven J Konezny
- ‡Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 08107-06520, United States
- §Energy Sciences Institute, Yale University, P.O. Box 27394, West Haven, Connecticut 06516-7394, United States
| | - C Moyses Araujo
- ‡Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 08107-06520, United States
- ⊥Yale Climate and Energy Institute (YCEI), Yale University, P.O. Box 208109, New Haven, Connecticut 06520-8109, United States
| | - Victor S Batista
- ‡Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 08107-06520, United States
- §Energy Sciences Institute, Yale University, P.O. Box 27394, West Haven, Connecticut 06516-7394, United States
- ⊥Yale Climate and Energy Institute (YCEI), Yale University, P.O. Box 208109, New Haven, Connecticut 06520-8109, United States
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Moyses Araujo C, Doherty MD, Konezny SJ, Luca OR, Usyatinsky A, Grade H, Lobkovsky E, Soloveichik GL, Crabtree RH, Batista VS. Tuning redox potentials of bis(imino)pyridine cobalt complexes: an experimental and theoretical study involving solvent and ligand effects. Dalton Trans 2012; 41:3562-73. [DOI: 10.1039/c2dt12195f] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Scheicher RH, Li S, Araujo CM, Blomqvist A, Ahuja R, Jena P. Theoretical study of C60 as catalyst for dehydrogenation in LiBH4. Nanotechnology 2011; 22:335401. [PMID: 21788688 DOI: 10.1088/0957-4484/22/33/335401] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Complex light metal hydrides possess many properties which make them attractive as a storage medium for hydrogen, but typically catalysts are required to lower the hydrogen desorption temperature and to facilitate hydrogen uptake in the form of a reversible reaction. The overwhelming focus in the search for catalysing agents has been on compounds containing titanium, but the precise mechanism of their actions remains somewhat obscure. A recent experiment has now shown that fullerenes (C(60)) can also act as catalysts for both hydrogen uptake and release in lithium borohydride (LiBH(4)). In an effort to understand the involved mechanism, we have employed density functional theory to carry out a detailed study of the interaction between this complex metal hydride and the carbon nanomaterial. Considering a stepwise reduction of the hydrogen content in LiBH(4), we find that the presence of C(60) can lead to a substantial reduction of the involved H-removal energies. This effect is explained as a consequence of the interaction between the BH(x)( - ) complex and the C(60) entity.
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Affiliation(s)
- Ralph H Scheicher
- Condensed Matter Theory Group, Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
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