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Sujith C, Joseph S, Mathew T, Mathew V. Ab initio investigation of the structural and electronic properties of tantalum thallium chalcogenides TaTlX3 (X = S,Se). J SOLID STATE CHEM 2022. [DOI: 10.1016/j.jssc.2022.123534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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2
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Sudrajat H, Susanti A, Hartuti S. Efficient electron extraction by CoS 2loaded onto anatase TiO 2for improved photocatalytic hydrogen evolution. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:344005. [PMID: 35762787 DOI: 10.1088/1361-648x/ac792d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Accepted: 06/15/2022] [Indexed: 06/15/2023]
Abstract
Titanium dioxide (TiO2) as a benchmark photocatalyst has been attracting attention due to its photocatalytic activity combined with photochemical stability. In particular, TiO2with anatase polymorph holds promise for driving reduction reactions, such as proton reduction to evolve H2via photocatalysis. In this study, anatase TiO2is loaded with CoS2through the hydrothermal route to form a CoS2@TiO2photocatalyst system. X-ray absorption near edge structure confirms the +2-oxidation state of the Co cation, while extended x-ray absorption fine structure shows that each Co2+cation is primarily coordinated to six S-anions forming a CoS2-like species. A small fraction of the Co2+species is also coordinated to O2-anions forming CoxOyspecies and substitutionally resides at the Ti4+-sites. Further investigations with steady-state IR absorption induced by UV-light and time-resolved microwave conductivity suggest an efficient electron transfer from the conduction band of TiO2to the surface-loaded CoS2which acts as a metallic material with no bandgap. The CoS2shallowly traps electrons at the host surface and facilitates proton reduction. An appreciably enhanced H2evolution rate (8 times) is recognised upon the CoS2loading. The CoS2is here proposed to function as a proton reduction cocatalyst, which can potentially be an alternative to noble metals.
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Affiliation(s)
- Hanggara Sudrajat
- Division of Computational Physics, Institute for Computational Science, Ton Duc Thang University, Ho Chi Minh City 700000, Vietnam
| | - Ari Susanti
- Department of Chemical Engineering, State Polytechnic of Malang, Malang 65141, Indonesia
| | - Sri Hartuti
- Department of Environmental and Renewable Energy Systems, Graduate School of Engineering, Gifu University, Gifu 501-1193, Japan
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Dzade NY. First-principles insights into the electronic structure, optical and band alignment properties of earth-abundant Cu 2SrSnS 4 solar absorber. Sci Rep 2021; 11:4755. [PMID: 33637815 PMCID: PMC7910308 DOI: 10.1038/s41598-021-84037-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 01/20/2021] [Indexed: 11/13/2022] Open
Abstract
Cu2SrSnS4 (CSTS) is a promising alternative candidate to Cu2ZnSnS4 (CZTS) for single- or multi-junction photovoltaics (PVs) owing to its efficient light-absorbing capability, earth-abundant, nontoxic constituents, and suitable defect properties. However, as a novel absorber material, several fundamental properties need to be characterized before further progress can be made in CSTS photovoltaics. In this letter, hybrid density functional theory (DFT) calculations have been used to comprehensively characterize for the first time, the electronic structure, band alignment, and optical properties of CSTS. It is demonstrated that CSTS possesses the ideal electronic structure (direct band gap of 1.98 eV and small photocarrier effective masses) and optical properties (high extinction coefficient and wide absorption) suitable for photovoltaic applications. Simulated X-ray photoelectron spectroscopy (XPS) valence band spectra using variable excitation energies show that Cu-3d electronic state dominates the valence band maximum of CSTS. Furthermore, the vacuum-aligned band diagram between CSTS and other common absorbers (CZTS, CIGS, CdTe) and the common n-type partner materials (CdS, ZnO) was constructed, which indicate staggered type-II band alignment at the CSTS/CdS and CSTS/ZnO interfaces. Based on these results, interface band offset engineering and alternative device architectures are suggested to improve charge carrier separation and power conversion efficiencies of CSTS.
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Affiliation(s)
- Nelson Y Dzade
- Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK.
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Varadwaj PR, Marques HM. The Cs 2AgRhCl 6 Halide Double Perovskite: A Dynamically Stable Lead-Free Transition-Metal Driven Semiconducting Material for Optoelectronics. Front Chem 2020; 8:796. [PMID: 33195026 PMCID: PMC7655969 DOI: 10.3389/fchem.2020.00796] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Accepted: 07/29/2020] [Indexed: 01/05/2023] Open
Abstract
A-Site doping with alkali ions, and/or metal substitution at the B and B'-sites, are among the key strategies in the innovative development of A 2BB'X6 halide double perovskite semiconducting materials for application in energy and device technologies. To this end, we have investigated an intriguing series of five halide-based non-toxic systems, A 2AgRhCl6 (A = Li, Na, K, Rb, and Cs), using density functional theory at the SCAN-rVV10 level. The lattice stability and bonding properties emanating from this study of A 2AgRhCl6 matched well with those that have already been synthesized, characterized and discussed [viz. Cs2AgBiX6 (X = Cl, Br)]. Exploration of traditional and recently proposed tolerance factors has enabled us to identify A 2AgRhCl6 (A = K, Rb and Cs) as stable double perovskites. The band structure and density of states calculations suggested that the electronic transition from the top of the valence band [Cl(3p)+Rh(4d)] to the bottom of the conduction band [(Cl(3p)+Rh(4d)] is inherently direct at the X-point of the first Brillouin zone. The (non-spin polarized) bandgap of these materials was found in the range 0.57-0.65 eV with SCAN-rVV10, which were substantially smaller than those computed with hybrid HSE06 and PBE0, and quasi-particle GW methods. This, together with the appreciable refractive index and high absorption coefficient in the region covering the range 1.0-4.5 eV, enabled us to demonstrate that A 2AgRhCl6 (A = K, Rb, and Cs) are likely candidate materials for photoelectric applications. The results of our phonon calculations at the harmonic level suggested that the Cs2AgRhCl6 is the only system that is dynamically stable (no imaginary frequencies found around the high symmetry lines of the reciprocal lattice), although the elastic moduli properties suggested all five systems examined are mechanically stable.
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Affiliation(s)
- Pradeep R. Varadwaj
- Department of Chemical System Engineering, School of Engineering, The University of Tokyo, Tokyo, Japan
- Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg, South Africa
| | - Helder M. Marques
- Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg, South Africa
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Ullattil SG, Jabeen Fatima MJ, Abdel-Wahab A. Defect minimized Ag-ZnO microneedles for photocatalysis. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2020; 27:37036-37043. [PMID: 32577972 PMCID: PMC7456407 DOI: 10.1007/s11356-020-09433-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 05/25/2020] [Indexed: 06/11/2023]
Abstract
A facile solution processing strategy has been developed for the formation of Ag-modified ZnO microneedles at various calcination temperatures such as 300, 500, and 700 °C (AZ3, AZ5, and AZ7 respectively). Due to the heavy doping of AgNO3, Ag+ ions have been incorporated in to the crystal lattice of ZnO in all the Ag-ZnO samples, which facilitated the formation of Ag-ZnO microneedle morphology with minimized defect states, and obviously, the plasmon peaks were observed due to Ag modification. These Ag-ZnO microneedle structures have been evaluated for their photocatalytic performance using methylene blue as model target contaminant and their activity was compared with the commercially available titania P25 photocatalyst. The photoactivity of all the Ag-ZnO microneedle structures was significantly higher than that of the commercially available P25 photocatalyst with the most active Ag-ZnO material having a photocatalytic activity ~ 1.4 times greater than that of P25 titania.
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Affiliation(s)
- Sanjay Gopal Ullattil
- Chemical Engineering Program, Texas A&M University at Qatar, 23874, Education City, Doha, Qatar.
| | - M J Jabeen Fatima
- Department of Nanoscience and Technology, University of Calicut, Malappuram, Kerala, 673635, India
| | - Ahmed Abdel-Wahab
- Chemical Engineering Program, Texas A&M University at Qatar, 23874, Education City, Doha, Qatar.
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First-Principles Investigation of the Structural, Elastic, Electronic, and Optical Properties of α- and β-SrZrS 3: Implications for Photovoltaic Applications. MATERIALS 2020; 13:ma13040978. [PMID: 32098231 PMCID: PMC7079647 DOI: 10.3390/ma13040978] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/11/2020] [Revised: 01/23/2020] [Accepted: 01/28/2020] [Indexed: 11/16/2022]
Abstract
Transition metal perovskite chalcogenides are attractive solar absorber materials for renewable energy applications. Herein, we present the first–principles screened hybrid density functional theory analyses of the structural, elastic, electronic and optical properties of the two structure modifications of strontium zirconium sulfide (needle–like α–SrZrS3 and distorted β–SrZrS3 phases). Through the analysis of the predicted electronic structures, we show that both α– and β–SrZrS3 materials are direct band gaps absorbers, with calculated band gaps of 1.38, and 1.95 eV, respectively, in close agreement with estimates from diffuse–reflectance measurements. A strong light absorption in the visible region is predicted for the α– and β–SrZrS3, as reflected in their high optical absorbance (in the order of 105 cm−1), with the β–SrZrS3 phase showing stronger absorption than the α–SrZrS3 phase. We also report the first theoretical prediction of effective masses of photo-generated charge carriers in α– and β–SrZrS3 materials. Predicted small effective masses of holes and electrons at the valence, and conduction bands, respectively, point to high mobility (high conductivity) and low recombination rate of photo-generated charge carriers in α– and β–SrZrS3 materials, which are necessary for efficient photovoltaic conversion.
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Samadi M, Sarikhani N, Zirak M, Zhang H, Zhang HL, Moshfegh AZ. Group 6 transition metal dichalcogenide nanomaterials: synthesis, applications and future perspectives. NANOSCALE HORIZONS 2018; 3:90-204. [PMID: 32254071 DOI: 10.1039/c7nh00137a] [Citation(s) in RCA: 116] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Group 6 transition metal dichalcogenides (G6-TMDs), most notably MoS2, MoSe2, MoTe2, WS2 and WSe2, constitute an important class of materials with a layered crystal structure. Various types of G6-TMD nanomaterials, such as nanosheets, nanotubes and quantum dot nano-objects and flower-like nanostructures, have been synthesized. High thermodynamic stability under ambient conditions, even in atomically thin form, made nanosheets of these inorganic semiconductors a valuable asset in the existing library of two-dimensional (2D) materials, along with the well-known semimetallic graphene and insulating hexagonal boron nitride. G6-TMDs generally possess an appropriate bandgap (1-2 eV) which is tunable by size and dimensionality and changes from indirect to direct in monolayer nanosheets, intriguing for (opto)electronic, sensing, and solar energy harvesting applications. Moreover, rich intercalation chemistry and abundance of catalytically active edge sites make them promising for fabrication of novel energy storage devices and advanced catalysts. In this review, we provide an overview on all aspects of the basic science, physicochemical properties and characterization techniques as well as all existing production methods and applications of G6-TMD nanomaterials in a comprehensive yet concise treatment. Particular emphasis is placed on establishing a linkage between the features of production methods and the specific needs of rapidly growing applications of G6-TMDs to develop a production-application selection guide. Based on this selection guide, a framework is suggested for future research on how to bridge existing knowledge gaps and improve current production methods towards technological application of G6-TMD nanomaterials.
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Affiliation(s)
- Morasae Samadi
- Department of Physics, Sharif University of Technology, Tehran 11155-9161, Iran.
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Opoku F, Govender KK, van Sittert CGCE, Govender PP. Understanding the mechanism of enhanced charge separation and visible light photocatalytic activity of modified wurtzite ZnO with nanoclusters of ZnS and graphene oxide: from a hybrid density functional study. NEW J CHEM 2017. [DOI: 10.1039/c7nj01942d] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
A hybrid ternary ZnS/GO/ZnO(001) system achieved enough driving force for splitting water into H2 gas.
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Affiliation(s)
- Francis Opoku
- Department of Applied Chemistry
- University of Johannesburg
- Johannesburg
- South Africa
| | - Krishna Kuben Govender
- Council for Scientific and Industrial Research
- Meraka Institute
- Center for High Performance Computing
- Cape Town
- South Africa
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Wang H, Qiao L, Xu H, Lin Y, Shen Y, Nan C. Anisotropy of Photocatalytic Properties in Nanostructured Photocatalysts. ACTA ACUST UNITED AC 2016. [DOI: 10.4236/snl.2016.62002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Zirak M, Ebrahimi M, Zhao M, Moradlou O, Samadi M, Bayat A, Zhang HL, Moshfegh AZ. Fabrication and surface stochastic analysis of enhanced photoelectrochemical activity of a tuneable MoS2–CdS thin film heterojunction. RSC Adv 2016. [DOI: 10.1039/c5ra26487a] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
CdS/MoS2(t)/ITO thin films were prepared via a facile method with controllable surface properties, and a model was proposed to describe the enhancement of photoelectrochemical activity from a stochastic view point.
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Affiliation(s)
- M. Zirak
- Department of Physics
- Sharif University of Technology
- Tehran
- Iran
| | - M. Ebrahimi
- Department of Physics
- Sharif University of Technology
- Tehran
- Iran
| | - M. Zhao
- State Key Laboratory of Applied Organic Chemistry
- College of Chemistry and Chemical Engineering
- Lanzhou University
- Lanzhou 730000
- P. R. China
| | - O. Moradlou
- Department of Chemistry
- Alzahra University
- Tehran
- Iran
| | - M. Samadi
- Department of Physics
- Sharif University of Technology
- Tehran
- Iran
| | - A. Bayat
- Department of Physics
- Sharif University of Technology
- Tehran
- Iran
| | - H.-L. Zhang
- State Key Laboratory of Applied Organic Chemistry
- College of Chemistry and Chemical Engineering
- Lanzhou University
- Lanzhou 730000
- P. R. China
| | - A. Z. Moshfegh
- Department of Physics
- Sharif University of Technology
- Tehran
- Iran
- Institute of Nanoscience and Nanotechnology
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On the Stability and Electronic Structure of Transition-Metal Dichalcogenide Monolayer Alloys Mo1−xXxS2−ySey with X = W, Nb. ELECTRONICS 2015. [DOI: 10.3390/electronics5010001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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