Constructing asymmetric active sites on defective Ru/W18O49 for photocatalytic nitrogen fixation

Defect engineering can offer active sites for N-2 adsorption and activation due to the abundant localized electrons of surface defects. However, the high energy barriers of the defect band can restrict the electron transfer, which thus limits the photocatalytic N-2 fixation performance. Herein, we demonstrate that Ru/W18O49 exhibits a nearly 6-fold enhanced photocatalytic activity for ammonia production under visible irradiation compared with pristine W18O49. Our investigations reveal that the enhanced photocatalytic N-2 fixation activities are mainly attributed to the synergistic effect of oxygen vacancies and Ru modification. The decorated Ru species can modify the coordination structure of oxygen vacancies by forming Ru-O-W bonds. The Ru-O-W centers can serve as active sites for the side-on adsorption of N-2 due to their asymmetric polarization, better promoting the electron transfer to absorbed N-2. Moreover, the LSPR between Ru and oxygen vacancies provides sufficient electrons for N-2 activation. As a result, the efficient electron transfer facilitates the activation and dissociation of N-2 on Ru/W18O49, which is feasible for the reduction of N-2 to NH3. This work provides a promising strategy for enhanced photocatalytic N-2 fixation by modulating defect engineering.