A‐site Substitution Motivating the Phase Transformation of LaNiO3 Perovskite for High‐Performance Artificial N2 Fixation

Electrocatalytic N-2 reduction reaction (NRR) to NH3 under ambient conditions is an attractive strategy compared to the traditional Haber-Bosch process. However, there still remains a great challenge due to the high activation barrier of N-2 and consequent sluggish kinetics. Herein, A-site substitution of LaNiO3 perovskites by Sr-doping is proposed which can lead to phase transformation and to the formation of oxygen vacancies, significantly improving the NRR performance of La1-xSrxNiO3 (LSNO). The appropriate oxygen vacancy concentration can be modulated by changing the stoichiometric ratio of La and Sr elements. LSNO-III (x=0.5) delivers the highest ammonia production rate of 55.9 mu g h(-1) mg(cat)(-1). at -0.7 V and Faraday efficiency of 23.17 % at -0.5 V versus the reversible hydrogen electrode in 0.1 M Na2SO4. Density functional theory (DFT) calculations further demonstrate that introduction of oxygen vacancies decreases the distance of the d-band center to the Fermi energy level, which not only facilitates adsorption and activation of N-2 molecules and subsequent hydrogenation reactions, but also further optimizes reaction pathways in NRR.