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−1cat, and the Faradaic efficiency(FE) is over 30%. [Display omitted] •The sandwich structure photoelectrocatalyst MCo2O4/MgO/BiVO4(M=Zn, Mn) was successfully prepared.•MgO acts as an intermediate layer to accelerate electron transport.•MCo2O4/MgO/BiVO4(M=Zn, Mn) PEC synthesis of ammonia is greatly improved.