Journal
CHEMISTRY-A EUROPEAN JOURNAL
Volume 18, Issue 48, Pages 15464-15475Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.201202149
Keywords
cobalt; electron transfer; hydrogen; photochemistry; supported catalysts
Categories
Funding
- EPSRC [EP/H00338X/2, EP/H046380/1]
- Christian Doppler Research Association (Austrian Federal Ministry of Economy, Family and Youth)
- Christian Doppler Research Association (National Foundation for Research, Technology and Development)
- OMV Group
- University of Cambridge
- Royal Society
- Spanish Ministry of Education [EX2010-0479]
- EPSRC [EP/H00338X/1, EP/H00338X/2, EP/H046380/1] Funding Source: UKRI
- Engineering and Physical Sciences Research Council [EP/H00338X/2, EP/H00338X/1, EP/H046380/1] Funding Source: researchfish
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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 degrees 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 molH2 (molCoP)-1 and above 200,000 molH2 (molTiO2 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 mu s 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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