Microenvironmental corrosion and hydrolysis induced two-dimensional heterojunction of copper oxide@ferriferrous oxide for efficient electrochemical nitrate reduction to ammonia

Electrochemical nitrate reduction (NO3RR) to ammonia could realize the green synthesis of ammonia and remove nitrate pollutant, which is of great significance to alleviate energy crisis and environmental problem. However, low ammonia selectivity and Faradic efficiency limits its further development. Herein, copper oxide @ ferriferrous oxide heterojunction (CuO NWAs@Fe3O4) was constructed by the in-situ growth of Cu(OH)2 nanowire arrays (Cu(OH)2 NWAs), microenvironmental corrosion and hydrolysis of Fe(NO3)3, and high-temperature pyrolysis. Because of CuO NWAs with excellent adsorption/activation of nitrate and Fe3O4 with high affinity for atomic hydrogen, the heterojunction demonstrated significantly improved NO3RR performance with nitrate conversion rate of 95.93%, ammonia selectivity of 88.68%, Faradaic efficiency of 97.46% and ammonia yield rate of 1.691 mmol h−1 cm−2 at −0.27 V vs. RHE. Moreover, this heterojunction displayed excellent durability with a high Faradaic efficiency of 94.45% after consecutive six cycles and a wide application range from 600 ppm to 2000 ppm. This work will lay the foundation for the design and fabrication of high-performance electrocatalysts for NO3RR.