Photoelectrochemical H2 Production

Photoelectrochemical H2 production, in which solar energy is directly converted to chemical energy by evolving H2 at the cathode and O2 at the anode of an electrochemical cell, has attracted intense interest lately. The cathode and anode materials are usually semiconductors with bandgaps in the energy range of visible light, but for H2 generation to be practical they must be inexpensive and stable. One of the few potential cathode materials is Cu2O. However, Cu2O is prone to "photocorrosion"-degradation under illumination, particularly with an applied bias. This project sought to create a more stable Cu2O-based heterojunction photocathode. The heterojunction was produced by electrodeposition of a p-type Cu2O thin film on a fluorine doped tin oxide (FTO) glass substrate, followed by spray pyrolysis deposition of an n-type ZnO layer. The effectiveness of the ZnO in protecting the Cu2O was evaluated from photocurrent measurements under 1kW Xe lamp illumination, with and without applied bias. The effect of the ZnO layer, the annealing temperature, the pH of the electrodeposition bath, and the thickness of the Cu2O films was studied.