A Method for Synthesis of Renewable Cu2O Junction Composite Electrodes and Their Photoelectrochemical Properties

We present a highly active copper oxide composite photoelectrode with improved stability and photoelectrochemical performance brought about by a simple cycle of heat treatment and cathodic reduction. Under one sun (AM 1.5 G, 100 mW/cm 2 ) light illumination, the photocurrent density of a Cu 2 O/CuO/Al 2 O 3 composite electrode was enhanced to −1.8 mA/cm 2 at 0 V vs RHE compared to −0.25 mA/cm 2 of the native Cu 2 O film. The improved stability of the film was demonstrated by ∼60% retention of initial photocurrent (−1.1 mA/cm 2 ) after 20 sequential cyclic voltammetry scans. Moreover the photocurrent showed only a slight decrease in activity after five regeneration cycles. Furthermore, a high incident photo-to-current efficiency (IPCE, 53% at 450 nm) was recorded. These enhancements in both photocurrent and stability are due to electron transfer from Cu 2 O to CuO and increase of carrier density due to the presence of Al 2 O 3 .