Dual-Coordinated Cu(I) Sites Immobilized on Ti₃C₂T_x MXene for Efficient Conversion of Low-Concentration Nitrate toward Ammonia

Copper-based materials have emerged as promising electrocatalysts for nitrate reduction. However, achieving efficient nitrate-to-ammonia conversion at low concentrations (usually ≤ 10 mmol L⁻¹) under neutral conditions remains a grand challenge. Here cooperative dual Cu⁺ sites are crafted on Ti₃C₂T_x MXene via coordination with the surface −O and −Cl functional groups, using an in situ self-reduction strategy, for electrochemical nitrate reduction. The resulting dual-active-site Cu(I)/Ti₃C₂T_x electrocatalyst achieves a NO₃⁻ removal efficiency of 97.6% and an ammonia selectivity of 94.7% in neutral wastewater containing 100 mg L⁻¹ NO₃⁻ at −0.8 V versus the reversible hydrogen electrode (RHE). Mechanistic investigations using in situ Raman spectroscopy, online differential electrochemical mass spectrometry (DEMS), and quantum chemical calculations reveal that the dual Cu⁺ sites, in conjunction with hydrogen-spillover facilitated by the Ti₃C₂T_x MXene, significantly enhance water dissociation to produce more absorbed active hydrogen. This process lowers the energy barrier for hydrogenating the *NO intermediate, which is regarded as the rate-determining step in Cu-based catalysts. Further the feasibility of an electrochemical NO₃⁻ reduction-coupled hydroponic fertilizing system is demonstrated for enabling simultaneous nitrate removal and wheat cultivation. This work provides a new paradigm for designing electrocatalysts to advance the “waste-to-wealth” conversion of nitrate-containing wastewater for sustainable agriculture.