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

Visible-light-driven N-2 reduction into NH3 in pure H2O provides an energy-saving alternative to the Haber-Bosch process for ammonia synthesizing. However, the thermodynamic stability of N equivalent to N and low water solubility of N-2 remain the key bottlenecks. Here, we propose a solution by developing a WO3-x hollow sphere with oxygen vacancies. Experimental analysis reveals that the hollow sphere structure greatly promotes the enrichment of N-2 molecules in the inner cavity and facilitates the chemisorption of N-2 onto 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 equivalent to N triple bonds. As such, the optimized catalyst shows a NH3 generation rate of 140.08 mu mol g(-1) h(-1), which is 7.94 times higher than the counterpart WO3-bulk.