Operando Oxygen Vacancies for Enhanced Activity and Stability toward Nitrogen Photofixation

Photocatalysts with oxygen vacancies (OVs) have exhibited exciting activity in N-2 photofixation due to their superiority in capture and activation of N-2. However, the surface OVs are easily oxidized by seizing the oxygen atoms from water or oxygen during the catalytic reaction. Here, it is reported that the grain boundaries (GBs) in nanoporous WO3 induce plenty of operando OVs under light irradiation to significantly boost catalytic activity toward N-2 photofixation. Impressively, nanoporous WO3 with abundant GBs (WO3-600) exhibit an ammonia production rate of 230 mu mol g(cat.)(-1) h(-1) without any sacrificial agents at room temperature, 17 times higher than that for WO3 nanoparticles without GBs. Moreover, WO3-600 also manifests remarkable stability by maintaining nearly approximate to 100% catalytic activity after ten successive reaction rounds. Further mechanistic studies reveal that both OVs and GBs regulate the band structures of WO3 nanocrystals, as well as favor the delivery of photogenerated electrons to adsorbed N-2 by enhancing W-O covalency. More importantly, plenty of operando OVs induced by GBs generate during catalytic reaction, directly contributing to the excellent catalytic performance for WO3-600. This work opens a novel avenue to developing efficient photocatalysts by construction of operando OVs.