Synergistic Spatial Confining Effect and O Vacancy in WO3 Hollow Sphere for Enhanced N2 Reduction

Visible-light-driven N2reduction into NH3in pure H2O provides an energy-saving alternative to the Haber–Bosch process for ammonia synthesizing. However, the thermodynamic stability of N≡N and low water solubility of N2remain the key bottlenecks. Here, we propose a solution by developing a WO3−xhollow sphere with oxygen vacancies. Experimental analysis reveals that the hollow sphere structure greatly promotes the enrichment of N2molecules in the inner cavity and facilitates the chemisorption of N2onto WO3−x-HS. The outer layer’s thin shell facilitates the photogenerated charge transfer and the full exposure of O vacancies as active sites. O vacancies exposed on the surface accelerate the activation of N≡N triple bonds. As such, the optimized catalyst shows a NH3generation rate of 140.08 μmol g−1h−1, which is 7.94 times higher than the counterpart WO3-bulk.Keywords:WO3;hollow sphere;O defect;N2reduction;photocatalysis