Fast and Selective Photoreduction of CO2 to CO Catalyzed by a Complex of Carbon Monoxide Dehydrogenase, TiO2, and Ag Nanoclusters [component]

unpublished
Selective, visible light-driven conversion of CO 2 to CO with a turnover frequency of 20 s −1 under visible light irradiation at 25 o C is catalyzed by an aqueous colloidal system comprising a pseudo-ternary complex formed between carbon monoxide dehydrogenase (CODH), silver nanoclusters stabilized by polymethacrylic acid (AgNCs-PMAA) and TiO 2 nanoparticles. The photocatalytic assembly which is stable over several hours and for at least 250,000 turnovers of the enzyme's active site, was
more » ... gated by separate electrochemical (dark) and fluorescence measurements to establish specific connectivities among the components. The data show (a) that a coating of AgNCs-PMAA on TiO 2 greatly enhances its ability as an electrode for CODH-based electrocatalysis of CO 2 reduction, and (b) that the individual Ag nanoclusters interact directly and dynamically with the enzyme surface, most likely at exposed cysteine thiols. The results lead to a model for photocatalysis in which the AgNCs act as photosensitizers, CODH captures the excited electrons for catalysis, and TiO 2 mediates hole transfer from the AgNC valence band to sacrificial electron donors. The results greatly increase the benchmark for reversible CO 2 reduction under ambient conditions and demonstrate that with such efficient catalysts, the limiting factor is the supply of photo-generated electrons.
doi:10.1021/acscatal.7b04308.s001 fatcat:dmt74aljffhvhokaeczj23c6vy