Insight into the in-situ surface reconstruction of perovskite BiFeO3 for boosting nitrate electroreduction to ammonia

Nitrate electroreduction (NO 3 RR) is a promising alternative route for green synthesis of ammonia, where high-efficient catalysts are desired. Herein, an inexpensive ABO 3 -type perovskite BiFeO 3 was demonstrated as a highly efficient NO 3 RR catalyst compared to most of the reported non-precious catalysts. More interestingly, a surface evolution is observed in conjunction with an enhancement in NH 3 yield rate during the NO 3 RR process. Numerous metallic Bi 0 clusters and oxygen vacancies (OVs) are in-situ generated in the reconstructed BiFeO 3 (RS-BiFeO 3 ), and are proposed to be the genuine active sites. Density functional theory calculations suggest the RS-BiFeO 3 promotes the conversion of *NO 2 to *NO and enhances the *H supply for NO 3 - hydrogenation, thus boosting NO 3 RR. The yield rate of NH 3 by the reconstructed BiFeO 3 electrode reaches 5.3 mg cm −2 h −1 with a Faradaic efficiency of 86.8% at −0.7 V vs . RHE, over 4 times higher than that of the pristine BiFeO 3 electrode. This study establishes a fundamental understanding of BiFeO 3 reconstruction during NO 3 RR, and provides insights for the rational design of perovskite NO 3 RR electrocatalysts.