Photoelectrochemical Reduction of CO2 Coupled to Water Oxidation Using a Photocathode with a Ru(II)–Re(I) Complex Photocatalyst and a CoO x /TaON Photoanode

Photoelectrochemical CO2 reduction activity of a hybrid photocathode, based on a Ru(II)–Re(I) supramolecular metal complex photocatalyst immobilized on a NiO electrode (NiO–RuRe), was confirmed in an aqueous electrolyte solution. Under half-reaction conditions, the NiO–RuRe photocathode generated CO with high selectivity, and its turnover number for CO formation reached 32 based on the amount of immobilized RuRe. A photoelectrochemical cell comprising a NiO–RuRe photocathode and a CoOx/TaON photoanode showed activity for visible-light-driven CO2 reduction using water as a reductant to generate CO and O2, with the assistance of an external electrical (0.3 V) and chemical (0.10 V) bias produced by a pH difference. This is the first example of a molecular and semiconductor photocatalyst hybrid-constructed photoelectrochemical cell for visible-light-driven CO2 reduction using water as a reductant.