Cobalt as a sacrificial metal to increase the photoelectrochemical stability of CuBi2O4 films for water splitting

CuBi2O4 is an excellent photocathode candidate in water-splitting photoelectrochemical cells. However, its poor photoelectrochemical stability caused by the reduction of Cu2+ to Cu metal limits its use. Here, we show a strategy to decrease the reduction of Cu2+ to Cu using cobalt as a sacrificial metal. Co-doped CuBi2O4 films were prepared by spray pyrolysis using Co2+ salt as the precursor. Co2+ ions replace Cu2+ in the CuBi2O4 structure, and subsequent heat treatment at 500 degrees C leads to partial oxidation of Co2+ to Co3+. As the reduction potential of Co3+/Co2+ is higher than that of Cu2+/Cu, Cu2+ reduction can be minimized. Comparatively, about 72% of the photocurrent produced by the CuBi2O4 film is lost in the first few minutes of illumination. In the Co-doped CuBi2O4 film, the photocurrent drops by less than 7%. Thus, the Co-doping can increase the CuBi2O4 photostability and be helpful for the fabrication of more stable photocathodes. (c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

CuBi2O4 is a promising photocathode material for water-splitting photoelectrochemical cells, but its poor stability due to Cu2+ reduction limits its application. This study presents a strategy to decrease Cu2+ reduction by using cobalt as a sacrificial metal. Co-doped CuBi2O4 films were prepared, and the reduction of Cu2+ was minimized by the partial oxidation of Co2+ to Co3+. Compared to the CuBi2O4 film, the Co-doped film exhibited a significantly lower drop in photocurrent, indicating enhanced photostability.