Efficient Electrochemical NO Reduction at Low Overpotential via Synergistic RuCu Alloy Nanoparticles

Abstract

Ammonia (NH3) synthesis via electrochemical nitric oxide reduction (NORR) has emerged as a promising alternative to the Haber-Bosch process, which requires high temperatures and pressures. However, NORR still faces critical challenges, including side reactions, limited mass transfer, and high overpotential requirements. Transition metals have been widely employed to address these issues owing to their favorable NO adsorption properties; however, they suffer from intermediate overbinding and require high overpotentials to achieve meaningful catalytic activity. To overcome these limitations, we introduce a noble-metal alloying strategy that combines the high electron-transfer kinetics of noble metals with the tunable NO adsorption properties of transition metals, thereby synergistically enhancing catalytic activity for selective NH3 production. We designed Ru-Cu alloy nanoparticles supported on nitrogen-doped carbon nanorods (Ru x Cu100-x @NCNR), and the optimized Ru5Cu95@NCNR catalyst exhibited an ammonia yield of 32.66 +/- 4.38 mu mol cm-2 h-1 and a Faradaic efficiency of 94 +/- 1.25% (FENH3) at -0.2 V vs RHE, notably lower overpotential than that reported for conventional NORR catalysts, demonstrating energy-efficient ammonia production. Long-term stability tests confirmed the sustained catalytic performance, and its practical applicability was further validated through integration into a Zn-NO battery system, highlighting its potential for next-generation energy conversion devices. Mechanistic investigations revealed that precise control of Ru content induces structural modulation of the RuCu alloy, thereby regulating the strength of NO adsorption and facilitating efficient protonation, ultimately governing high NH3 selectivity.