The effect of thin titanium layers on Cu₂O photocathodes for solar water splitting

Abstract Cu 2 O is considered a promising material for constructing viable photocathodes for solar H 2 generation with a theoretical efficiency of 18%. However, its main drawback is photocorrosion, which occurs during operation in aqueous solution. Photocorrosion leads to a degradation of photocatalytic activity. In this study, a thin titanium layer was deposited on the Cu 2 O surface to enhance its stability. We investigated the effect of Ti thickness on the performance of the Cu 2 O electrode. The results indicate that a 10 nm Ti layer promotes charge separation, while thicker layers lead to the accumulation of photoelectrons at the Ti/ Cu 2 O interface, thereby increasing the recombination of photo-generated carriers. The optimal Ti-protected Cu 2 O photocathode, achieved with a 10 nm Ti layer, exhibits a current density of 0.70 mA cm −2 at 0 V versus RHE and retains approximately 40% of its initial photocurrent after 3 min of operation.