Ni₂P-Ni dual-active-site tandem electrocatalysis enables ampere-level current density for nitrate reduction to...

Electrocatalytic nitrate reduction to ammonia (e-NO₃⁻RR) holds great promise for environmental remediation and sustainable energy conversion. However, its industrial application is hindered by the sluggish kinetics of the eight-electron transfer process and the competitive hydrogen evolution reaction (HER), which result in low ammonia yield and Faradaic efficiency (FE). This paper develops an innovative Ni₂P-Ni/NF catalyst. At -0.4 V (vs. RHE), it yields 85.35 mg h⁻¹ cm⁻² of ammonia with a FE of 95.55 % and removes 99.4 % of nitrate within 2.5 h. In-situ characterizations reveal a tandem catalytic mechanism: Ni₂P facilitates efficient NO₃⁻ → NO₂⁻ conversion, while grain boundary defects (GB) metallic Ni enriches reactive hydrogen (*H) to suppress HER and drive NO₂⁻ → NH₃ hydrogenation. This synergistic interaction optimizes the reaction pathway for efficient NH₃ production. Moreover, a gas stripping-absorption system is employed to demonstrate the complete conversion to high-purity ammonium chloride, highlighting practical applicability. By replacing the conventional oxygen evolution reaction with glycerol oxidation, an energy-efficient bifunctional system is established, further enhancing overall catalytic efficiency. This work provides a sustainable strategy for direct conversion of nitrate pollutants to nitrogen fertilizers and opens new avenues for green ammonia synthesis.