Synergistic dual-vacancies and La single-atom engineering over S-Scheme WS2-x/La1-WO2.9 heterojunction for efficient N2-to-NH3 photosynthesis

Photocatalytic nitrogen fixation (PNF) under mild conditions is a promising approach to sustainable ammonia (NH 3 ) synthesis. However, PNF normally encounters many challenges, such as inefficient charge separation, poorly exposed active sites, and sluggish multi-electron/proton-involved steps. Here, we design a step (S)-scheme WS 2-x /La 1 -WO 2.9 heterojunction through integrating rich oxygen/sulfur dual-vacancies and loading rare-earth La single atoms. The as-prepared photocatalyst achieves a high NH 3 generation rate of 124.9 μmol∙g −1 ∙h −1 , which is 4.4, 1.7 and 1.2-fold those of pristine WO 3-x , WS 2-x and WS 2-x /WO 2.9 , respectively. Further in-depth characterizations and theoretical calculations reveal a synergistic photocatalytic effect in WS 2-x /La 1 -WO 2.9 , mainly due to the regulated collaborative dual defects and a lower energy d −π* occupation orbital from the modulation of La-modified W site. This leads to significantly reducing the reaction barrier in the rate-limiting step and elucidating the key intermediate processes (-NH 2 , -NH 2 NH 2 ) of the nitrogen fixation reaction. Our study creates a comprehensive strategy, analogous to the “three birds with one stone” method, offering new insights into advancing PNF.