Enhancing photoelectrocatalytic activity and stability of p-Cu2O photocathode through n-TiO2 coating for improved H2 evolution reaction

Abstract This article presents a novel approach to improve both the photoelectrocatalytic activity and stability of the p-Cu 2 O photocathode. The approach involves the coating of an n-type TiO 2 layer using e-beam evaporation with precise controllability of the coating thickness onto the p-type Cu 2 O electrode, forming a TiO 2 /Cu 2 O p/n heterojunction. Such a p/n junction enhances the photoelectrocatalytic activity of the Cu 2 O electrode by promoting the separation of the photo-generated charge carriers. Additionally, the large bandgap TiO 2 coating layer serves as protection, reducing the photocorrosion of Cu 2 O, thereby improving the stability of the electrode. The n-TiO 2 /p-Cu 2 O photocathode shows superior photoelectrochemical H 2 evolution activity in comparison to the pristine p-Cu 2 O photocathode. We have found that the thickness and annealing temperature of TiO 2 influence strongly the photocurrent and stability of the resultant TiO 2 /Cu 2 O photocathode. The best TiO 2 /Cu 2 O photocathode was achieved by coating a 50 nm thick TiO 2 layer onto the Cu 2 O, followed by annealing at 350 °C. This configuration exhibited a large onset photovoltage of 0.58 V vs RHE and a catalytic current density of ∼0.9 mA·cm ‒2 at 0 V vs RHE in a pH 7 phosphate buffer, under standard 1 Sunlight illumination.