Synthesis of Ultrathin Mesoporous Cu_xRu Nanomeshes for Efficient Kilowatt‐Level Nitrate Reduction to Ammonia

The electrochemical conversion of abundant nitrate ions from industrial wastewater and polluted groundwater into value-added ammonia represents an important route for the sustainable development of human society. However, developing efficient and stable catalysts remains a huge challenge. Herein, the synthesis of ultrathin mesoporous Cu_xRu nanomeshes is reported via a theory-guided ion exchange method for efficient nitrate reduction to ammonia. The prepared Cu_xRu nanomeshes are composed of Cu atoms anchored ultrathin mesoporous Ru nanomeshes, with a thickness of ≈2-3 nm and a pore distribution between 2 and 10 nm. It offers a high nitrate reduction performance, including a positive onset potential (0.41 V), a high ammonia Faradaic efficiency (94.5%) and a highest ammonia mass activity (0.7 A mg^-1) at 0 V up to date. Moreover, a kilowatt-level nitrate reduction is first verified in a flow electrolyzer, with the fastest reported NO₃ ^- removal velocity of 12.4 mmol min^-1. In situ characterizations and theoretical calculations clearly reveal that Cu atoms can balance the energy barriers in nitrate reduction and competitive hydrogen evolution reactions, leading to improved catalytic performance.