Dual-active-site design of FeNi3 for electrocatalytic nitrate reduction to ammonia

Simultaneously enhancing the adsorption of nitrate (NO3-) and the supply of active hydrogen is crucial for achieving excellent performance in nitrate reduction to ammonia (NRA). However, it remains a formidable challenge due to their competitive adsorption. Herein, we develop a dual-active-site strategy using FeNi3 as a model catalyst. This strategy enables Ni site to adsorb and dissociate H2O, supplying active hydrogen, while the Fe site adsorbs and reduces NO3-. The strong interaction between Ni and Fe in FeNi3 optimizes the electronic structure of both active sites, thereby enhancing the adsorption capacity of NO3 - and active hydrogen supply concurrently. As a result, FeNi3 exhibits a significantly enhanced NH3 Faradaic efficiency (FENH3) of 95.5 % at -0.35 V versus reversible hydrogen electrode (vs. RHE), along with a NH3 yield rate of 381.2 mu mol h- 1 cm-2 at -0.45 V vs. RHE, surpassing those of Fe, Ni and most reported catalysts. Additionally, a two-electrode coupling system integrating NRA and oxygen evolution reaction (OER) is constructed based on FeNi3, requiring an ultralow voltage of 1.70 V to achieve 10 mA cm-2 and realizing a high FENH3 of 94.1 % at 2.1 V.