Scanning photoelectrochemical study of Cu2O thin films coated by oxide and metallic overlayers

The increasing global energy demand, coupled with the objective of keeping CO2 atmospheric concentrations under 450 ppm, creates the need for efficient energy storage. For this purpose, hydrogen is an enticing choice. Hydrogen to electricity and combustion processes are already well studied and viable, with harmless H2O as a byproduct. To produce hydrogen the use of solar energy would be ideal. To this end, photoelectrochemical cells represent an option with theoretically high efficiency and a simple monolithic structure. Among all the materials for the realization of photocathode, Cu2O is widely available, non-toxic, and has the appropriate bandgap. In this work, a Cu2O on F-doped SnO2 (FTO) on glass photocathode is modified and studied. Some functionalization layers were deposited on the sample and their role was studied by employing a novel high throughput setup and fabrication procedure. Specifically, an electron transport layer made of Al doped ZnO (AZO), a passivation layer made of TiO2, and a nickel molybdenum catalyst were added to the sample. The photoelectrochemical characterization shows that further optimization is needed in order to protect the Cu2O film from photocorrosion and improve electron transfer from the photocathode to the electrolyte, while preserving an efficient electron transport efficiency to the surface.