Carbon Nanotube–Supported CuNi Coating Structure Catalysts with Dense, Uniform Shells for Efficient and Stable Nitrate‐to‐Ammonia Electrocatalysis

Comprehensive Summary Electrocatalytic nitrate (NO 3 – ) reduction to ammonia (NO 3 RR) attracts attention for its mild conditions and ability to convert NO 3 – pollutants into valuable ammonia, yet achieving high yield and long‐term stability at low overpotentials remains a major challenge. Here, a homemade carbon paper (HCP) catalyst support with high specific surface area, excellent conductivity, and robust structural stability was constructed from carbon nanotubes (CNTs). Leveraging the uniform surface properties and high surface energy of carbon nanotubes, active CuNi metals self‐assemble to form a uniform, dense coating structure with a shell thickness of approximately 3 nm. This structure maximizes active‐site exposure and facilitates rapid, spatially coupled tandem reactions during NO 3 RR within the same interfacial region, thereby boosting overall catalytic performance, while the intrinsically high surface energy of CNTs thermodynamically suppresses Ostwald ripening of the metal components, conferring excellent long‐term catalytic stability. Meanwhile, efficient electrocatalytic NO 3 RR at low potentials was achieved by tuning NO 3 – adsorption via Cu and promoting the hydrogenation process through Ni. As a result, the CuNi/HCP catalyst delivered an NH 3 production rate of 16.73 mg·h –1 ·cm –2 at –0.08 V vs. RHE (~90% FE), increasing to 27.15 mg·h –1 ·cm –2 and 96.85% FE at –0.28 V, with stable operation over 456 h.