Enhanced photocatalytic CO 2 reduction to CO and CH 4 over gold-decorated cuprous oxide (Au-Cu 2 O) composites

This study synthesised gold-decorated cuprous oxide (Au-Cu2O) photocatalysts via a precipitation method for the photoreduction of carbon dioxide (CO2) to carbon monoxide (CO) and methane (CH4). The Au loading was varied to optimise photocatalytic performance and quantum yield. The materials were comprehensively characterised by XRD, SEM, TEM, and XPS to analyse their crystal structure, morphology, composition, and electronic properties, thereby informing the proposed reaction mechanism. Results indicate that the 0.1 wt% Au-Cu2O composite exhibited the highest activity under 15 W green LED irradiation, producing 33.50 μmol g− 1 of CH4 and 23.85 μmol g−1 of CO. The corresponding quantum yields for CH4 and CO were 0.35% and 0.06%, respectively, representing a 1.6-fold enhancement over pristine Cu2O. Based on the experimental and characterisation data, a plausible photocatalytic mechanism for CO2 reduction on the Au-Cu2O surface is proposed.