Enhancing nitrate reduction to ammonia by synergistic and interface coupling effects of binary metal sites

Electrochemical nitrate reduction to ammonia (NRA) provides a sustainable and energy-efficient technical solution. Herein, we reported a synergistic bimetallic oxides Fe3O4/SnO2/NF with heterointerfaces for efficient NRA. The interfacial charge transfer at the heterointerfaces between Fe3O4 and SnO2 improves the adsorption and activation of nitrate and intermediates, and strongly inhibits the production of by-products (NO2−) and the occurrence of HER. Experimental and theoretical results verify that the Fe sites activate NO3−, while the Sn sites dissociate H2O molecules to provide necessary *H for the Fe sites to reduce NO3−. Benefiting from the interfacial engineering and synergistic effect of Fe and Sn, Fe3O4/SnO2/NF exhibits excellent NRA performance (NH3 Faradaic efficiency: 98.78%, NH3 yield: 0.2584 mmol h−1 cm−2, NH3 selectivity: 98.85%, and NO3− conversion: 90.19%), which is significantly superior to Fe3O4/NF and SnO2/NF. This work provides a powerful approach for constructing synergistic heterojunction and contribute a promising strategy for designing efficient electrocatalysts.