Cu2O 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, Cu2O 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 Cu2O/BaZrO3 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 Cu2O films and spin coated over-layer of BaZrO3, and optimize its PEC performance with thickness of Cu2O film. We find a maximum photocurrent density of 1.25 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 Cu2O and BaZrO3 with stable PEC performance and understanding of the mechanism of charge separation across the Cu2O/BaZrO3 interface developed here should facilitate further optimization of Cu2O/BaZrO3 films for realistic PEC applications. (C) 2017 Elsevier Ltd. All rights reserved.