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 H evolution and CO 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 CO 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.