New strategy for the enhanced electrocatalytic reduction of nitrate: Construction of charge polarization by interfacial engineering

Modulating the adsorption of nitrate ions and intermediates is an effective strategy to enhance the electrocatalytic performance on the conversion of NO₃⁻ to NH₃. Here, a Cu₁Ni₁/NiFeP/Nickel foam (NF) nanosheet array electrode with heterointerfaces was designed and synthesized to achieve high-performance nitrate reduction to ammonia (NRA). The interfacial charge polarization at the heterointerface between CuNi and NiFeP induces an electron deficiency on the Cu surface, enhancing the adsorption of nitrate ions. Experimental and theoretical calculations confirmed that Cu sites regulate the adsorption of nitrate ions and intermediates during NRA, whereas Ni and NiFeP sites facilitate the dissociation of water molecules and provide *H to Cu sites on demand. Owning to the combination of Cu, Ni, and NiFeP tandem catalytic sites, Cu₁Ni₁/NiFeP/NF exhibited a significant synergistic effect with a synergy index of 60.0 %. When the initial NO₃⁻-N concentration was 100 mg L⁻¹, the NRA performance of Cu₁Ni₁/NiFeP/NF (NO₃⁻-N conversion: 98.9 %, Faradaic efficiency: 94.0 %, NH₃-N yield: 537.0 μg h⁻¹ cm⁻², and NH₃-N selectivity: 87.3 %) significantly outperformed that of the Cu₁Ni₁/NF and NiFeP/NF electrodes. This study elucidates the mechanism of the enhanced NRA process at the Cu₁Ni₁/NiFeP heterointerface, and provides an efficient and sustainable approach for treating nitrate-containing wastewater.