Surface-controlled oxygen vacancy-rich Bi/BiVO4 Schottky junction for highly selective and active photocatalytic nitrogen fixation

The modulation of active site density and localized electron concentration represents a crucial step in enhancing nitrogen activation, thereby significantly augmenting the efficiency of photocatalytic nitrogen fixation. In this paper, Bi/BiVO4 Schottky junctions enriched with oxygen vacancies (Bi/Vo-BVO) were fabricated by in situ reduction. Compared to BiVO4, Bi/Vo-BVO composites exhibited 8.4-fold enhancement in ammonia synthesis yield, reaching a maximum rate of 167.74 mu mol center dot g(-1)center dot h(-1). In situ FTIR spectroscopy and isotopic labeling experiments definitively demonstrated that the nitrogen constituent of NH4+ is derived from N-2. N-2-TPD and DFT calculation collectively suggest that the surface of Bi/Vo-BVO, enriched with ligand-unsaturated V4+ species, furnishes a substantial array of chemisorption sites for N-2 molecules, attributed to the abundance of oxygen vacancies. In situ XPS coupled with DFT corroborate that the photoexcited electrons within the BiVO4 valence band accumulate in the conduction band, thereby directly facilitating the activation of N-2 adsorbed at the V4+ active sites; The built-in electric field established at the interface between Bi and BiVO4 substantially facilitates the enrichment of Bi-emitted thermal electrons within oxygen vacancies on BiVO4 surface. These electrons subsequently migrate towards and interact with the adsorbed N-2 via the V4+ active sites. The synergistic photothermal electrons activation mechanism of N-2 not only enhances the efficiency of light energy utilization but maximizes the catalytic efficacy of the photocatalyst through the full exploitation of its intrinsic catalytic potential.