MOFs-derived CuNi alloy on honeycomb carbon with highly efficient electrocatalytic reduction of nitrate to ammonia

Electrocatalytic nitrate reduction reaction (NO₃RR) provides a promising route for restoring nitrogen cycle balance and achieving sustainable ammonia production. However, in the neutral electrolyte with low nitrate concentrations, the NO₃RR performance is unsatisfactory. Primarily due to the competing hydrogen evolution reaction, inefficient hydrogenation, and slow nitrate mass transfer, collectively hinder its further application. Herein, a three-dimensional honeycomb-shaped carbon-supported CuNi alloy nanostructure derived from a MOFs precursor was prepared via a rapid joule heating method. Owing to the synergistic effect between Cu and Ni, the Cu_0.81Ni_0.19-JH alloy exhibited an NH₃ production rates as high as 5.24 mg h^-1 cm^-2 with a Faradaic efficiency of 86.90% at -0.75 V (vs. RHE). In situ FT-IR spectroscopy and experimental evidence revealed that Cu sites were primarily responsible for the adsorption and activation of NO₃^-, while Ni sites continuously supplied *H to sustain the reaction, thereby ensuring highly efficient NO₃RR. Furthermore, the Cu_0.81Ni_0.19-JH electrode was applied to simulate nitrate wastewater, achieving a nitrate removal efficiency of 99.54% after 12.5 h. In a co-electrolyte system with Cl^-/SO₄^2- (1:1, molar ratio), the N₂ selectivity was maintained at a high level (>99%) across the entire testing range, along with the nitrate removal efficiency of 98.87% after 30 h. Furthermore, the electrode was assembled into a Zn-NO₃^- battery, demonstrating promising application prospects.