Improved Conductivity and in Situ Formed Heterojunction via Zinc Doping in CuBi₂O₄ for Photoelectrochemical Water...

As a photocathode with a band gap of about 1.8 eV, copper bismuthate (CuBi₂O₄) is a promising material for photoelectrochemical (PEC) water splitting. However, weak charge transfer capability and severe carrier recombination suppress the PEC performance of CuBi₂O₄. In this paper, the conductivity and carriers transport of CuBi₂O₄ are improved via introducing Zn²⁺ into the synthesis precursor of CuBi₂O₄, driving a beneficial 110 mV positive shift of onset potential in photocurrent. Detailed investigations demonstrate that the introduction of an appropriate amount of zinc leads to in situ segregation of ZnO which serves as an electron transport channel on the surface of CuBi₂O₄, forming heterojunctions. The synergistic effect of heterojunctions and doping simultaneously promotes the charge transfer and the carrier concentration. OCP experiment proves that ZnO/Zn-CuBi₂O₄ possesses better charge separation; the Mott-Schottky curve shows that the doping of Zn significantly enhances the carrier concentration; carrier lifetime calculated from time-resolved photoluminescence confirms faster extraction of carriers.