Perovskite oxide LaMO3-δ (M = Fe, Co, Ni and Cu) cathode for efficient electroreduction of nitrate

• Perovskite oxide LaMO 3-δ cathodes were applied for NO 3 – -N electroreduction. • La 2 CuO 4 exhibited best catalytic performance as its super electrochemical property. • The selectivity of NH 4 + -N and N 2 were 82.4 ± 2.2% and 9.4 ± 2.4%, respectively. • Both electron- and H*-mediated pathway occurred for NO 3 – -N electroreduction. • Oxygen vacancies and redox cycle of Cu(I)-Cu(II)-Cu(I) worked for NO 3 – -N reduction. Electroreduction removal of nitrate (NO 3 – -N) is considered as a promising approach to solve its adverse effects on environment and human health, where efficient and cheap catalysts are required. Perovskite-based catalysts showed a versatile catalytic ability for wide range of redox reactions, but seldom applied for NO 3 – -N reduction. Herein, four perovskite oxide cathodes, LaMO 3-δ (M = Fe, Co, Ni and Cu) were prepared and used for the reduction of NO 3 – -N. The Ruddlesden-Popper (RP) type La 2 CuO 4 exhibited the best NO 3 – -N catalytic activity among the four perovskite oxide cathodes, with a removal rate of 11.7 × 10 -3 min −1 . The high selectivity of NH 4 + -N (82.4 ± 2.2%) indicated that NH 4 + -N was the main final product for NO 3 – -N electroreduction at La 2 CuO 4 cathode, but 100% of N 2 selectivity could be obtained with addition of 1000 and 1500 mg/L Cl - as the electro-assisted chlorination process. The mechanism of NO 3 – -N electroreduction occurred by both electron- and H*-mediated pathway, and the oxygen vacancies and redox cycle of Cu(I)-Cu(II)-Cu(I) were proposed as the accommodation sties and direct electron sources for NO 3 – -N reduction. Generally, this study opens a novel avenue for the development of earth-abundant, cost-effective catalyst with effective NO 3 – -N electroreduction.