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Understanding the dynamics of molecular water oxidation catalysts with liquid phase transmission electron microscopy: the case of vitamin B12
Date
2021
Abstract
Cobalt compounds are intensely explored as efficient catalysts for the oxygen evolution reaction (OER). Since vitamin B12 is a soluble cobalt compound with high enzymatic activity, evaluating its OER activity is of high relevance for bio-mimetic catalyst research. In this work, the temporal evolution of the homogenous vitamin B12 catalyst in the early stages of OER was investigated by an advanced combination of in situ electrochemical liquid transmission electron microscopy (EC-LTEM), in situ UV-vis spectroelectrochemistry, and extended X-ray absorption fine structure (EXAFS) methods. For the first time, we provided direct evidence of diffuse layer dynamics on the working electrode interface. The results suggested that the formation of cobalt oxyphosphate nanoparticles on the working electrode interface and in the presence of phosphate buffer is the initial stage of the catalytic pathway. Computational results confirmed that the ligand oxidation pathway could occur at potentials below the OER thermodynamic barrier (1.23 V vs. RHE), which leads to Co ion leaching into the electrolyte. This study showed that investigation of the apparent molecular mechanisms of OER with metal complexes requires careful analyses. We illustrate the high precision and sensitivity of EC-LTEM under operational conditions to monitor heterogeneous catalysts generated during OER and to evaluate their actual roles in the catalytic process.
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Description
Publisher
American Chemical Society
Citation
ACS Sustainable Chemistry & Engineering, 2021, 9, (28), pp. 9494–9505
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Funding Information
MMN and ZA are grateful to the Institute for Advanced Studies in Basic Sciences and Science Elites Federation. GRP and SEB thank the Swiss National Science Foundation (Sinergia Grant No. CRSII2_160801/1) and the UZH Research Priority Program Solar Light to Chemical Energy Conversion (URPP LightChEC) for financial support. GRP and SEB thank Dr. Maarten Nachtegaal and Dr. Olga Safonova for support and access to the SuperXAS beamline to carry out XAS experiments at PSI. SEB and ASS thank Dr. Xing Huang for his support in TEM data evaluation. SIA was supported by the grant from the Russian Science Foundation (no: 19-14-00118). M.V. wishes to acknowledge the Irish Centre for High-End Computing (ICHEC) for the provision of computational facilities and support.