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Towards optimized H2-evolving photocathodes by a molecular strategy

Abstract : Production of solar fuels in a dye-sensitized hydrogen-evolving photoelectrochemical cell, where splitting of water into H2 and O2 occurs is an attractive method in order to fulfill future energy demands and face the environmental problems arising by the combustion of fossil fuels. The group constructed a functional NiO DS-photocathode for H2 evolution, a counterpart of the tandem device, based on the first noble metal-free covalent dye-catalyst assembly. Here, we report the synthesis and characterization of two novel dye-catalyst assemblies, both relying on the same ruthenium photosensitizer. The first dyad is based on the cobalt diimine-dioxime complex previously employed by the group and the second one on a cobalt tetraazomacrocyclic complex. Photoelectrochemical experiments under identical conditions enabled us to correlate the performance with the choice of the photosensitizer and the catalyst. Ruthenium outperformed in activity photocathodes based on organic dyes. Transient absorption spectroelectrochemistry revealed that one limiting factor for the activity of our systems is the thermal electron transfer from the reduced dye to the catalytic unit. In addition, post-operando analysis showed that desorption of the molecular architecture from the surface and decomposition of the cobalt diimine-dioxime also limits the efficiency. The second dye-catalyst assembly exhibits the higher TON ever reported for dye-sensitized hydrogen-evolving photocathodes, implying that more stable and robust catalysts are of significant importance. Finally, the second dyad was functional for PEC CO2 reduction to CO under aqueous media with promising preliminary results.
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Submitted on : Tuesday, January 4, 2022 - 2:46:15 PM
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  • HAL Id : tel-03510383, version 1

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Emmanouil Giannoudis. Towards optimized H2-evolving photocathodes by a molecular strategy. Inorganic chemistry. Université Grenoble Alpes [2020-..], 2020. English. ⟨NNT : 2020GRALV005⟩. ⟨tel-03510383⟩

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