Enhanced Photocatalytic CO2 Reduction over Ni-doped Bi4O5Br2/NiCo2O4 Heterojunction: Synergistic Enhancement Effect between Spin Polarization and Built-in Electric Field

The development of high-performance photocatalysts is crucial for enabling efficient CO2 conversion in photocatalytic systems. Here, we developed a novel heterojunction (N-BON) composed of Ni-doped Bi4O5Br2 and NiCo2O4 for CO2 photoreduction with the help of simulated sunlight. The optimized 21N-BON composite exhibited the highest activity, producing 18.66 μmol·g–1·h–1 of CO with a selectivity of 95.7%, which represents a remarkable 2.15-fold and 4.75-fold increase in CO yield compared to the Bi4O5Br2/NiCo2O4 heterojunction and Ni-doped Bi4O5Br2, respectively. Photoelectrochemical testing, photoluminescence analysis, and theoretical calculations demonstrated that the enhanced performance of the 21N-BON composite is attributed to improved photogenerated carrier separation, driven by the synergistic effects of Ni-doping-induced spin polarization and the built-in electric field from heterojunction construction. Additionally, theoretical calculations and in situ DRIFTS analyses was used to clarify the CO2 reaction mechanisms on the photocatalyst surface, showing that Ni doping improved CO2 adsorption and promoted the formation of key reaction intermediates. This study offers important guidance for developing advanced photocatalysts for solar-driven CO2 reduction, contributing to sustainable energy solutions.