Electron Transfer in Dye‐Sensitised Semiconductors Modified with Molecular Cobalt Catalysts: Photoreduction of Aqueous Protons |
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Authors: | Fezile Lakadamyali Dr Anna Reynal Dr Masaru Kato Prof James R Durrant Dr Erwin Reisner |
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Affiliation: | 1. Christian Doppler Laboratory for Sustainable SynGas Chemistry, Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW (UK);2. Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ (UK) |
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Abstract: | A visible‐light driven H2 evolution system comprising of a RuII dye ( RuP ) and CoIII proton reduction catalysts ( CoP ) immobilised on TiO2 nanoparticles and mesoporous films is presented. The heterogeneous system evolves H2 efficiently during visible‐light irradiation in a pH‐neutral aqueous solution at 25 °C in the presence of a hole scavenger. Photodegradation of the self‐assembled system occurs at the ligand framework of CoP , which can be readily repaired by addition of fresh ligand, resulting in turnover numbers above 300 mol H2 (mol CoP )?1 and above 200,000 mol H2 (mol TiO2 nanoparticles)?1 in water. Our studies support that a molecular Co species, rather than metallic Co or a Co‐oxide precipitate, is responsible for H2 formation on TiO2. Electron transfer in this system was studied by transient absorption spectroscopy and time‐correlated single photon counting techniques. Essentially quantitative electron injection takes place from RuP into TiO2 in approximately 180 ps. Thereby, upon dye regeneration by the sacrificial electron donor, a long‐lived TiO2 conduction band electron is formed with a half‐lifetime of approximately 0.8 s. Electron transfer from the TiO2 conduction band to the CoP catalysts occurs quantitatively on a 10 μs timescale and is about a hundred times faster than charge‐recombination with the oxidised RuP . This study provides a benchmark for future investigations in photocatalytic fuel generation with molecular catalysts integrated in semiconductors. |
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Keywords: | cobalt electron transfer hydrogen photochemistry supported catalysts |
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