Si-doped Cu2O/SiOx composites for efficient photoelectrochemical water reduction

Abstract

Cuprous oxide (Cu2O) is an attractive photo-electrocatalyst for sustainable hydrogen production. The main issues limiting the use of Cu2O as a photocathode are the severe electron-hole recombination and photo-corrosion in aqueous electrolyte. Herein, to address the above issues, amorphous SiOx overlayers have been deposited on the surface of Cu2O as a protective cover using a facile dip-coating method. The overall PEC performances have been greatly improved, as evidenced by the increased photocurrent density (3.1 times of bare Cu2O) and improved stability (3.8 times of bare Cu2O). The structure and PEC characterizations prove that Si has been gradient-doped into the Cu2O, leading to a downward band bending from the bulk to the surface region, which promotes the charge separation and transfer efficiently. In addition, the amorphous SiOx layers serve as protection layers and prevent the Cu2O from direct contact with the electrolyte, maintaining a high photocurrent density over the stability test. Decoration with Pt catalyst has further boosted the photocurrent density to be 2.8 mA cm−2 at 0 V vs. RHE with better stability, indicating the synergistic effect of SiOx layer and Pt catalyst This work provides a facile strategy to improve the PEC activity and stability of Cu2O, which may be extended to other systems with photo-corrosion problems, such as BiVO4 or ZnO.