Ru‐Incorporation‐Induced Phase Transition in Co Nanoparticles for Low‐Concentration Nitric Oxide Electroreduction to Ammonia at Low Potential

Abstract Electrocatalytic reduction of nitric oxide (NO) to ammonia (NH 3 ) represents a potential solution for improving the disrupted nitrogen cycle balance. Unfortunately, designing efficient electrocatalysts for NO reduction reaction (NORR) remains a notable challenge, especially at low concentrations. Herein, a displacement‐alloying strategy is reported to successfully induce the phase transition of Co nanoparticles supported on carbon nanosheets from face‐centered cubic (fcc) to hexagonal close‐packed (hcp) structure through Ru incorporation. The obtained RuCo alloy with hcp phase structure (hcp‐RuCo) exhibits apparent NORR activity with a record‐high Faraday efficiency of 99.2% and an NH 3 yield of 77.76 µg h −1 mg cat −1 at −0.1 V versus reversible hydrogen electrode at a NO concentration of 1 vol %, surpassing Co nanoparticles with fcc phase structure and most reported catalysts. Density functional theory calculations reveal that the excellent NORR activity of hcp‐RuCo can be attributed to the optimized electronic structure of Co site and lowered energy barrier of the potential rate‐determining step through phase transition. Furthermore, the assembled Zn‐NO battery using hcp‐RuCo as the cathode achieves a power density of 2.33 mW cm −2 and an NH 3 yield of 45.94 µg h −1 mg cat −1 . This work provides a promising research perspective for low‐concentration NO conversion.