In situ grown Fe3O4 particle on stainless steel: A highly efficient electrocatalyst for nitrate reduction to ammonia

NH3 is an essential feedstock for fertilizer synthesis. Industry-scale NH3 synthesis mostly relies on the Haber-Bosch method, however, which suffers from massive CO2 emission and high energy consumption. Electrocatalytic NO3− reduction is an attractive substitute to the Haber-Bosch method for synthesizing NH3 under mild conditions. As this reaction will produce a variety of products, it highly desires efficient and selective electrocatalyst for NH3 generation. Here, we report in situ grown Fe3O4 particle on stainless steel (Fe3O4/SS) as a high-efficiency electrocatalyst for NO3− reduction to NH3. In 0.1 M NaOH with 0.1 M NaNO3, such Fe3O4/SS reaches a remarkable Faradaic efficiency of 91.5% and a high NH3 yield of 10,145 µg·h−1·cm−2 at −0.5 V vs. reversible hydrogen electrode (RHE). Furthermore, it owns robust structural and electrochemical stability. This work provides useful guidelines to expand the scope of metallic oxide electrocatalysts for NH3 synthesis. The catalytic mechanism is uncovered and discussed further by theoretical calculations.