The composite electrocatalyst BFSO/BFO was prepared by one-step hydrothermal method, which has high activity and selectivity toward NRR. [Display omitted] The Haber-Bosch N 2 fixation method suffers from the power-consuming and harsh conditions. In contrast, the electrochemical conversion of N 2 (NRR) at room temperature and atmospheric pressure is considered a promising alternative route. In this study, we synthesized Sb-modified with Bi 25 FeO 40 (BFSO/BFO) by using one-step hydrothermal treatment. The BFSO/BFO catalyst has higher selectivity to NRR than Bi 25 FeO 40 (BFO) under the same applied voltage. Such large interfacial interaction area plays a critical role in transfer electron and enhances the density of current. The resulting BFSO/BFO heterojunction showed significant electrocatalytic activity under controllable voltage, which exhibited favorable average ammonia (NH 3) yield as high as 2.62 μg·h−1·cm−2 at −0.2 V versus RHE. Moreover, the stability of the BFSO/BFO composite was evaluated for six cycles and the results were desirable. This study provides a new insight into the design of composite catalysts using BFO, which has high activity and selectivity toward NRR. [ABSTRACT FROM AUTHOR]