Active Hydrogen-Switchable Dynamic Oxygen Vacancies in MoO3–x upon Ru Nanoparticle Decoration for Boosting Photocatalytic Ammonia Synthesis Performance

Simultaneous promotion of N 2 adsorption and NH 3 desorption, which is referred to as breaking the scaling relationship, is a major challenge in the photocatalytic ammonia synthesis reaction. Herein, we have successfully developed an active hydrogen (H*)-switchable dynamic oxygen vacancy (OV) evolution strategy for solving this problem on MoO 3– x decorated by Ru nanoparticles (Ru/MoO 3– x ). In this strategy, H* drives the cyclic dynamic evolution of the OVs between the initial state Ru/MoO 3– x and intermediate state Ru/MoO 3– x N y, which exhibit strong capabilities for N 2 adsorption and NH 3 desorption, respectively. The combination of in situ characterization and DFT calculation reveals that the strong interaction between N 2 and OVs in Ru/MoO 3– x induces the spontaneous formation of Ru/MoO 3– x N y, whereas this nitrogen species filling the OVs promotes the H* spillover from Ru to MoO 3– x, thereby accelerating the hydrogenation of lattice N and the desorption of NH 3 . As a result, the 6.5 wt % Ru/MoO 3– x achieves an ammonia production rate of 192.38 μmol·g –1 ·h –1, 2.68-fold higher than that of pristine MoO 3– x . Besides, nitrate reduction and nitric oxide reduction to synthesize NH 3 further verified this strategy, which exhibited a performance of 370 and 220 μmol·g –1 ·h –1, respectively. This study opens an avenue for a catalytic reaction with scaling relationship.