Spinel-covered interlayer MgO enhances the performance of BiVO₄ photocatalytic ammonia synthesis

In order to respond to the call for low emissions and low energy consumption, photoelectrochemical (PEC) ammonia synthesis is used to replace the Haber-Bosch method of nitrogen reduction, and highly efficient photoelectrocatalysts were used to reduce the reaction energy barrier. In this paper, the interlayer MgO and base BiVO₄ were successfully compounded by a simple electrodeposition method, and the spinel MCo₂O₄ (M=Zn, Mn) was compounded on MgO/BiVO₄ by a hydrothermal method, forming a sandwich structure of MCo₂O₄/MgO/BiVO₄ (M=Zn, Mn). The research shows that the sandwich structure constructed by MgO as the intermediate layer can reduce the excessive surface defects of photocatalyst, effectively reduce the recombination of photogenerated charge, promote the directional migration and separation of photogenerated charge, and improve the photocurrent density and photoelectric conversion efficiency. MCo₂O₄ (M=Zn, Mn) is a nitrogen reduction cocatalyst, which forms a heterojunction with n-type BiVO₄ and inhibits the recombination of photogenerated electrons. The synergistic effect of MCo₂O₄(M=Zn, Mn) and MgO accelerates the surface charge transfer efficiency and enhances the photoelectricity ammonia synthesis efficiency. The PEC ammonia synthesis efficiency reached more than 30 µmol h⁻¹ g⁻¹_cat, and the Faradaic efficiency(FE) is over 30%.