Role of oxygen vacancies in plasma‑catalytic ammonia synthesis over MnOx/MgAl LDH

This work systematically investigates the role of catalyst oxygen vacancies in plasma‑catalyzed ammonia synthesis over MnOx/LDH. Experiments show that the MnOx/LDH‑500 catalyst with the highest surface oxygen vacancy concentration achieves an ammonia concentration of 12,056 ppm, which is 1.54 times that obtained with the bare LDH support possessing the lowest vacancy content, 1.27 times that of MnOx/LDH-300, and 1.33 times that of MnOx/LDH-700. Meanwhile, the energy yield increased significantly with the increase of oxygen vacancies. The MnOx/LDH-500 catalyst achieved an energy yield of 1.10 g·kWh-1, which is 1.54 times that of the bare LDH support. In situ optical diagnostics reveal that the key intermediate excited N2 is first generated in the gas phase and then adsorbed onto the catalyst surface to form NHx species for ammonia formation. The benefit of oxygen vacancies lies in providing surface sites for excited N2 adsorption. These findings offer scientific guidance and a practical strategy for designing efficient catalysts compatible with plasma processes.