A Method for Synthesis of Renewable Cu 2 O 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/cm2) light illumination, the photocurrent density of a Cu2O/CuO/Al2O3 composite electrode was enhanced to −1.8 mA/cm2 at 0 V vs RHE compared to −0.25 mA/cm2 of the native Cu2O film. The improved stability of the film was demonstrated by ∼60% retention of initial photocurrent (−1.1 mA/cm2) 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 Cu2O to CuO and increase of carrier density due to the presence of Al2O3.