Electronic band-offsets across Cu2O/BaZrO3 heterojunction and its stable photo-electro-chemical response: First-principles theoretical analysis and experimental optimization

Abstract Cu 2 O has been shown to be highly active as a cathode in photo-electro-chemical (PEC) reduction of water to generate hydrogen fuel using sunlight. However, Cu 2 O is susceptible to photo-corrosion when exposed to an electrolyte and needs to be protected by an over-layer of a suitable material, and its performance depends sensitively on its interface with the over-layer, and hence to the method of deposition. Here, we use first-principles theoretical analysis of the electronic structure of Cu 2 O/BaZrO 3 interface, and show that valence and conduction bands are favourably aligned to absorb light and catalyse the Hydrogen Evolution Reaction. We then present experiments with spray pyrolytically deposited Cu 2 O films and spin coated over-layer of BaZrO 3 , and optimize its PEC performance with thickness of Cu 2 O film. We find a maximum photocurrent density of1.25 mA/cm 2 at 0.95 V/SCE for an overall thickness of 458 nm, and demonstrate that the photocurrent remains stable over a long period of time. Demonstration of scalable and cost effective deposition of Cu 2 O and BaZrO 3 with stable PEC performance and understanding of the mechanism of charge separation across the Cu 2 O/BaZrO 3 interface developed here should facilitate further optimization of Cu 2 O/BaZrO 3 films for realistic PEC applications.