Hybrid photocathode consisting of a CuGaO₂ p-type semiconductor and a Ru(<scp>ii</scp>)–Re(<scp>i</scp>) supramolecular photocatalyst: non-biased visible-light-driven CO₂ reduction with water oxidation

Abstract

A CuGaO₂ p-type semiconductor electrode was successfully employed for constructing a new hybrid photocathode with a Ru(ii)-Re(i) supramolecular photocatalyst (<b>RuRe</b>/CuGaO₂). The <b>RuRe</b>/CuGaO₂ photocathode displayed photoelectrochemical activity for the conversion of CO₂ to CO in an aqueous electrolyte solution with a positive onset potential of +0.3 V <i>vs.</i> Ag/AgCl, which is 0.4 V more positive in comparison to a previously reported hybrid photocathode that used a NiO electrode instead of CuGaO₂. A photoelectrochemical cell comprising this <b>RuRe</b>/CuGaO₂ photocathode and a CoO _<i>x</i> /TaON photoanode enabled the visible-light-driven catalytic reduction of CO₂ using water as a reductant to give CO and O₂ without applying any external bias. This is the first self-driven photoelectrochemical cell constructed with the molecular photocatalyst to achieve the reduction of CO₂ by only using visible light as the energy source and water as a reductant.