Adjusting the Covalency of Metal‐Oxygen Bonds in CuBi₂O₄ by Zn Cation Doping to Achieve Highly Efficient Photocathodes

Zn doped CuBi₂O₄ photocathodes are prepared by using a low-cost solution-based spray pyrolysis method. The doping of Zn in CuBi₂O₄ promotes the separation and migration of carriers and effectively increases the carrier density. Compared with CuBi₂O₄ alone, the photoelectrochemical activity of the Zn doped CuBi₂O₄ photoelectrode is improved with the photocurrent density of -0.56 mA/cm² at 0.4 V vs. RHE. This improvement is due to the lower electronegativity of Zn, which leads to the covalent increase of Cu-O and Bi-O bonds in CuBi₂O₄, which limits the recombination of photogenerated electrons and holes and improves charge separation and transport. This study presents an innovative approach to enhance the charge separation efficiencies of photocathodes by implementing element doping strategies, which may contribute to further research on photocatalytic water splitting.