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

Abstract

AbstractElectrocatalytic N2 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 N2 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 μg h−1 mg−1cat. 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 N2 molecules and subsequent hydrogenation reactions, but also further optimizes reaction pathways in NRR.