Widely Controllable Syngas Production by a Dye‐Sensitized TiO₂ Hybrid System with Re^I and Co^III Catalysts under Visible‐Light Irradiation

Abstract

Visible-light irradiation of a ternary hybrid catalyst prepared by grafting a dye, an H₂ evolving Co^III catalyst and a CO-producing Re^I catalyst on TiO₂ have been found to produce both H₂ and CO (syngas) in CO₂ -saturated N,N-dimethyl formamide (DMF)/water solution containing a 0.1 m sacrificial electron donor. The H₂ /CO ratios are effectively controlled by changing either the water content of the solvent or the molar ratio of the Re^I and Co^III catalysts ranging from 1:2 to 15:1. The controlled syngas formation is discussed in terms of competitive electron flow from TiO₂ to each of the CO₂ -reduction and hydrogen-evolving sites depending on the efficiencies of the two catalytic reaction cycles under given reaction conditions.