Decoration of Cu2O photocathode with protective TiO2 and active WS2 layers for enhanced photoelectrochemical hydrogen evolution.

A Cu2O based multi-layered photocathode was fabricated with a layer-by-layer assembly method for enhanced photoelectrochemical (PEC) hydrogen evolution. Au was first electrodeposited on the fluorine-doped tin oxide glass to decrease the electrochemical impedance of the Cu2O photocathode. A layer of TiO2 was then coated to increase the light-to-electricity energy conversion efficiency and the chemical stability by forming a p-n junction with Cu2O. Exfoliated WS2 nanosheets obtained from lithium insertion were then coated as the electron acceptor to facilitate the hydrogen evolution. This photocathode is effective for PEC hydrogen evolution, and a photocurrent of -10 mA cm-2 can be obtained at -0.33 V versus RHE in a phosphorus buffer (pH = 6.0) under visible light (λ ≥ 420 nm, 100 mW cm-2) on the optimized photocathode.