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.