Constructing Mo5+ sites in molybdenum oxide by lattice stress for efficient ammonia synthesis

Molybdenum oxide (MoO 3 ) is a promising catalyst for electrocatalytic nitrogen reduction (eNRR). However, Mo sites with saturated coordination are not favorable to stable N 2 adsorption. Herein, we employed sodium ions as electron donors to interact with the interlayer atoms of MoO 3 , causing localized lattice stress on it and weakening the M-O bond, thus inducing the Mo 5+ active sites (Na x MoO 3 ). The N 2 temperature-programmed desorption (N 2 -TPD) result of the as-prepared Na x MoO 3 exhibits that introducing Mo 5+ could significantly improve the N 2 adsorption on the catalyst’s surface. The optimized Na x MoO 3 has an NH 3 yield of 41.3 μg h −1 mg −1 at ambient temperature and an FE of 21.4 %, which is in the relatively advanced position in the contemporaneous studies. Both experiments and density-functional theory (DFT) calculation demonstrated that the Mo 5+ sites can effectively reduce the d-orbital energy level of Mo, which significantly enhances the interaction with N 2 .