A gold-coupled ZnTe/ZnO-nanowire array is a new photocathode for selective CO2 reduction to CO. At −0.7 VRHE under simulated 1 sun illumination, its photocurrent 

(−16.0 mA cm⁻²) and incident photon-to-current conversion efficiency (97%) represent the highest among reported ZnTe photocathodes for CO2 reduction and dramatic enhancement from those of a bare electrode (−7.9 mA cm⁻², 68%). In addition, the Au nanoparticles convert mainly-hydrogen-producing bare ZnTe/ZnO-nanowires into mainly-CO-producing photocathodes in photoelectrochemical CO2 reduction. The remarkable effects of the Au co-catalyst originate from the formation of a Schottky junction with ZnTe to improve charge separation and to provide reaction centers for CO2 reduction suppressing competing water reduction.