All-solid-state mechanochemical synthesis of Cu²⁺-doped MIL-53(Fe) for high-efficient nitrate electroreduction to ammonia

Electrocatalytic nitrate reduction has emerged as a promising strategy for sustainable ammonia synthesis, providing the dual advantage of mitigating nitrate pollution and producing valueadded green ammonia. However, enhancing intrinsic catalytic activity and catalytic site accessibility remains a challenge for further improving the performance of nitrate electroreduction to ammonia. Herein, a series of gradient Cu 2+ -doped MIL-53(Fe) electrocatalysts were synthesized via an all-solid-state mechanochemical synthesis method for electrocatalytic nitrate-to-ammonia conversion. MIL-53(Fe)-CuB exhibits a large NH 3 production rate of 2391±327 μg h -1 mgcat -1 at -0.6 V vs. NHE and a high faradaic efficiency of 82.1±1.2% at -0.3 V vs. NHE in 1 M KOH with 100 ppm NO 3 --N, demonstrating an excellent electrocatalytic performance for nitrate reduction. This work reveals that Cu 2+ -doping in mechanochemically synthesized Fe-MOFs boosts nitrate reduction efficiency and selectivity, while broadening research on foreign metal ion anchoring in MOF electrocatalysis.