Copper–zinc oxide heterostructure photocathodes for hydrogen and methanol production

Low activity and a short lifetime are the main weaknesses of photocatalysts. The photoactivity of copper oxide, which is known as one of the most promising materials for H2 evolution and CO2 reduction, can be improved by coupling with other semiconductors. This effect is based on a mutual charge transfer. The photocathode developed in this work, based on a CuO–ZnO composite with mutual self-doping, exhibits attractive photoelectrochemical properties, in particular a high density of generated photocurrent lasting for 24 h. Under visible light irradiation, the composite produces water-splitting, while in the presence of carbon dioxide it is able to perform CO2 reduction to methanol with good selectivity coupled to water oxidation. The high activity of the CuO-based cathode is due to the presence of zinc oxide, which is progressively leached, causing a slow decrease of the photoactivity of the material.