Hybrid photocathode consisting of a CuGaO p-type semiconductor and a Ru(ii)-Re(i) supramolecular photocatalyst: non-biased visible-light-driven CO reduction with water oxidation.

A CuGaO p-type semiconductor electrode was successfully employed for constructing a new hybrid photocathode with a Ru(ii)-Re(i) supramolecular photocatalyst (/CuGaO). The /CuGaO photocathode displayed photoelectrochemical activity for the conversion of CO to CO in an aqueous electrolyte solution with a positive onset potential of +0.3 V Ag/AgCl, which is 0.4 V more positive in comparison to a previously reported hybrid photocathode that used a NiO electrode instead of CuGaO. A photoelectrochemical cell comprising this /CuGaO photocathode and a CoO /TaON photoanode enabled the visible-light-driven catalytic reduction of CO using water as a reductant to give CO and O without applying any external bias. This is the first self-driven photoelectrochemical cell constructed with the molecular photocatalyst to achieve the reduction of CO by only using visible light as the energy source and water as a reductant.