Photoelectrochemical CO 2 reduction by Cu 2 O/Cu 2 S hybrid catalyst immobilized in TiO 2 nanocavity arrays

Photoelectrocatalytic CO 2 reduction to CO was achieved on Cu 2 O/Cu 2 S nanoparticles which are immobilized in TiO 2 nanocavity array. The Cu 2 S shell was obtained by ions exchange reaction of O 2− and S 2− on the surface of Cu 2 O by a chemical vapor deposition with Na 2 S precursor. This coating can protect the Cu 2 O nanoparticle from photocorrosion during photocatalysis. The lower resistance and plasmonic absorbance endow a superior activity of the Cu 2 O/Cu 2 S heterostructures toward photoelectrochemical reduction of CO 2 . It exhibits a current density of 10.7 mA cm −2 at the overpotential of − 0.26 V with a CO faradaic efficiency (FE) higher than 81%. The excellent photo-assisted catalytic performance (photo-induced current increment is more than 50%) is attributed to the localized surface plasmonic resonance of Cu 2 S coatings and highly ordered hierarchical structure of the Cu 2 O/Cu 2 S nanoparticles, which facilitate charge carrier separation and mass transfer. These hybrid electrodes demonstrate a long-term stability by resisting photocorrosion within 5 h with a higher FE of CO 2 to CO conversion.