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Brands M, Reek JNH. Mechanistic Insights into Electrocatalytic Hydrogen Evolution by an Exceptionally Stable Cobalt Complex. Inorg Chem 2024; 63:8484-8492. [PMID: 38640469 PMCID: PMC11080059 DOI: 10.1021/acs.inorgchem.4c01043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2024] [Revised: 04/05/2024] [Accepted: 04/09/2024] [Indexed: 04/21/2024]
Abstract
Co(aPPy) is one of the most stable and active molecular first-row transition-metal catalysts for proton reduction reported to date. Understanding the origin of its high performance via mechanistic studies could aid in developing even better catalysts. In this work, the catalytic mechanism of Co(aPPy) was electrochemically probed, in both organic solvents and water. We found that different mechanisms can occur depending on the solvent and the acidity of the medium. In organic solvent with a strong acid as the proton source, catalysis initiates directly after a single-electron reduction of CoII to CoI, whereas in the presence of a weaker acid, the cobalt center needs to be reduced twice before catalysis occurs. In the aqueous phase, we found drastically different electrochemical behavior, where the Co(aPPy) complex was found to be a precatalyst to a different electrocatalytic species. We propose that in this active catalyst, the pyridine ring has dissociated and acts as a proton relay at pH ≤ 5, which opens up a fast protonation pathway of the CoI intermediate and results in a high catalytic activity. Furthermore, we determined with constant potential bulk electrolysis that the catalyst is most stable at pH 3. The catalyst thus functions optimally at low pH in an aqueous environment, where the pyridine acts as a proton shuttle and where the high acidity also prevents catalyst deactivation.
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Affiliation(s)
- Maria
B. Brands
- Homogeneous, Supramolecular and Bio-inspired
Catalysis, Van ‘t Hoff Institute
for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Joost N. H. Reek
- Homogeneous, Supramolecular and Bio-inspired
Catalysis, Van ‘t Hoff Institute
for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
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2
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Kavun V, Uslamin E, van der Linden B, Canossa S, Goryachev A, Bos EE, Garcia Santaclara J, Smolentsev G, Repo E, van der Veen MA. Promoting Photocatalytic Activity of NH 2-MIL-125(Ti) for H 2 Evolution Reaction through Creation of Ti III- and Co I-Based Proton Reduction Sites. ACS APPLIED MATERIALS & INTERFACES 2023; 15:54590-54601. [PMID: 37966899 PMCID: PMC10694822 DOI: 10.1021/acsami.3c15490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 11/01/2023] [Accepted: 11/02/2023] [Indexed: 11/17/2023]
Abstract
Titanium-based metal-organic framework, NH2-MIL-125(Ti), has been widely investigated for photocatalytic applications but has low activity in the hydrogen evolution reaction (HER). In this work, we show a one-step low-cost postmodification of NH2-MIL-125(Ti) via impregnation of Co(NO3)2. The resulting Co@NH2-MIL-125(Ti) with embedded single-site CoII species, confirmed by XPS and XAS measurements, shows enhanced activity under visible light exposure. The increased H2 production is likely triggered by the presence of active CoI transient sites detected upon collection of pump-flow-probe XANES spectra. Furthermore, both photocatalysts demonstrated a drastic increase in HER performance after consecutive reuse while maintaining their structural integrity and consistent H2 production. Via thorough characterization, we revealed two mechanisms for the formation of highly active proton reduction sites: nondestructive linker elimination resulting in coordinatively unsaturated Ti sites and restructuring of single CoII sites. Overall, this straightforward manner of confinement of CoII cocatalysts within NH2-MIL-125(Ti) offers a highly stable visible-light-responsive photocatalyst.
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Affiliation(s)
- Vitalii Kavun
- Department
of Separation Science, LUT University, FI-53850 Lappeenranta, Finland
| | - Evgeny Uslamin
- Department
of Chemical Engineering, Delft University
of Technology, 2629 HZ Delft, The
Netherlands
| | - Bart van der Linden
- Department
of Chemical Engineering, Delft University
of Technology, 2629 HZ Delft, The
Netherlands
| | - Stefano Canossa
- Department
of Nanochemistry, Max Planck Institute for
Solid State Research, 70569 Stuttgart, Germany
| | - Andrey Goryachev
- Department
of Chemical Engineering, Delft University
of Technology, 2629 HZ Delft, The
Netherlands
| | - Emma E. Bos
- Department
of Chemical Engineering, Delft University
of Technology, 2629 HZ Delft, The
Netherlands
| | - Jara Garcia Santaclara
- Department
of Chemical Engineering, Delft University
of Technology, 2629 HZ Delft, The
Netherlands
| | | | - Eveliina Repo
- Department
of Separation Science, LUT University, FI-53850 Lappeenranta, Finland
| | - Monique A. van der Veen
- Department
of Chemical Engineering, Delft University
of Technology, 2629 HZ Delft, The
Netherlands
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5
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Singh V, Gupta N, Hargenrader GN, Askins EJ, Valentine AJS, Kumar G, Mara MW, Agarwal N, Li X, Chen LX, Cordones AA, Glusac KD. Photophysics of graphene quantum dot assemblies with axially coordinated cobaloxime catalysts. J Chem Phys 2020; 153:124903. [PMID: 33003752 DOI: 10.1063/5.0018581] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report a study of chromophore-catalyst assemblies composed of light harvesting hexabenzocoronene (HBC) chromophores axially coordinated to two cobaloxime complexes. The chromophore-catalyst assemblies were prepared using bottom-up synthetic methodology and characterized using solid-state NMR, IR, and x-ray absorption spectroscopy. Detailed steady-state and time-resolved laser spectroscopy was utilized to identify the photophysical properties of the assemblies, coupled with time-dependent DFT calculations to characterize the relevant excited states. The HBC chromophores tend to assemble into aggregates that exhibit high exciton diffusion length (D = 18.5 molecule2/ps), indicating that over 50 chromophores can be sampled within their excited state lifetime. We find that the axial coordination of cobaloximes leads to a significant reduction in the excited state lifetime of the HBC moiety, and this finding was discussed in terms of possible electron and energy transfer pathways. By comparing the experimental quenching rate constant (1.0 × 109 s-1) with the rate constant estimates for Marcus electron transfer (5.7 × 108 s-1) and Förster/Dexter energy transfers (8.1 × 106 s-1 and 1.0 × 1010 s-1), we conclude that both Dexter energy and Marcus electron transfer process are possible deactivation pathways in CoQD-A. No charge transfer or energy transfer intermediate was detected in transient absorption spectroscopy, indicating fast, subpicosecond return to the ground state. These results provide important insights into the factors that control the photophysical properties of photocatalytic chromophore-catalyst assemblies.
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Affiliation(s)
- Varun Singh
- Department of Chemistry, University of Illinois at Chicago, 845 W Taylor Street, Chicago, Illinois 60607, USA
| | - Nikita Gupta
- Department of Chemistry, University of Illinois at Chicago, 845 W Taylor Street, Chicago, Illinois 60607, USA
| | - George N Hargenrader
- Department of Chemistry, University of Illinois at Chicago, 845 W Taylor Street, Chicago, Illinois 60607, USA
| | - Erik J Askins
- Department of Chemistry, University of Illinois at Chicago, 845 W Taylor Street, Chicago, Illinois 60607, USA
| | - Andrew J S Valentine
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, USA
| | - Gaurav Kumar
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Michael W Mara
- Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 Cass Ave., Lemont, Illinois 60439, USA
| | - Neeraj Agarwal
- School of Chemical Sciences, UM DAE Centre for Excellence in Basic Sciences, University of Mumbai, Kalina, Santacruz (E), Mumbai 400098, India
| | - Xiaosong Li
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, USA
| | - Lin X Chen
- Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 Cass Ave., Lemont, Illinois 60439, USA
| | - Amy A Cordones
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Ksenija D Glusac
- Department of Chemistry, University of Illinois at Chicago, 845 W Taylor Street, Chicago, Illinois 60607, USA
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6
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Hu Y, Zhan F, Wang Q, Sun Y, Yu C, Zhao X, Wang H, Long R, Zhang G, Gao C, Zhang W, Jiang J, Tao Y, Xiong Y. Tracking Mechanistic Pathway of Photocatalytic CO 2 Reaction at Ni Sites Using Operando, Time-Resolved Spectroscopy. J Am Chem Soc 2020; 142:5618-5626. [PMID: 32130002 DOI: 10.1021/jacs.9b12443] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Harvesting solar energy for catalytic conversion of CO2 into valuable chemical fuels/feedstocks is an attractive yet challenging strategy to realize a sustainable carbon-cycle utilization. Homogeneous catalysts typically exhibit higher activity and selectivity as compared with heterogeneous counterparts, benefiting from their atomically dispersed catalytic sites and versatile coordination structures. However, it is still a "black box" how the coordination and electronic structures of catalysts dynamically evolve during the reaction, forming the bottleneck for understanding their reaction pathways. Herein, we demonstrate to track the mechanistic pathway of photocatalytic CO2 reduction using a terpyridine nickel(II) complex as a catalyst model. Integrated with a typical homogeneous photosensitizer, the catalytic system offers a high selectivity of 99% for CO2-to-CO conversion with turnover number and turnover frequency as high as 2.36 × 107 and 385.6 s-1, respectively. We employ operando and time-resolved X-ray absorption spectroscopy, in combination with other in situ spectroscopic techniques and theoretical computations, to track the intermediate species of Ni catalyst in the photocatalytic CO2 reduction reaction for the first time. Taken together with the charge dynamics resolved by optical transient absorption spectroscopy, the investigation elucidates the full mechanistic reaction pathway including some key factors that have been often overlooked. This work opens the "black box" for CO2 reduction in the system of homogeneous catalysts and provides key information for developing efficient catalysts toward artificial photosynthesis.
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Affiliation(s)
- Yangguang Hu
- Hefei National Laboratory for Physical Sciences at the Microscale, iChEM, School of Chemistry and Materials Science, and National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Fei Zhan
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.,Chemistry and Chemical Engineering Guangdong Laboratory, Shantou, Guangdong 515031, China
| | - Qian Wang
- Hefei National Laboratory for Physical Sciences at the Microscale, iChEM, School of Chemistry and Materials Science, and National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yujian Sun
- Hefei National Laboratory for Physical Sciences at the Microscale, iChEM, School of Chemistry and Materials Science, and National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Can Yu
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xuan Zhao
- Department of Physics, Beijing Normal University, Beijing 100875, China
| | - Hao Wang
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.,Chemistry and Chemical Engineering Guangdong Laboratory, Shantou, Guangdong 515031, China
| | - Ran Long
- Hefei National Laboratory for Physical Sciences at the Microscale, iChEM, School of Chemistry and Materials Science, and National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Guozhen Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale, iChEM, School of Chemistry and Materials Science, and National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Chao Gao
- Hefei National Laboratory for Physical Sciences at the Microscale, iChEM, School of Chemistry and Materials Science, and National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Wenkai Zhang
- Department of Physics, Beijing Normal University, Beijing 100875, China
| | - Jun Jiang
- Hefei National Laboratory for Physical Sciences at the Microscale, iChEM, School of Chemistry and Materials Science, and National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Ye Tao
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
| | - Yujie Xiong
- Hefei National Laboratory for Physical Sciences at the Microscale, iChEM, School of Chemistry and Materials Science, and National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230026, China.,Dalian National Laboratory for Clean Energy, Dalian, Liaoning 116023, China
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