Title : Applied potential-dependent structural evolution of copper nanoparticles during electrochemical nitric oxide reduction to ammonia
Abstract:
The electrochemical nitric oxide reduction reaction (NORR) to ammonia (NH3) provides a sustainable route for clean energy and chemical production, with copper (Cu) serving as a leading catalyst owing to its high selectivity. However, the dynamic behavior of Cu under NORR conditions remains poorly understood. In this study, we investigate the potential-dependent morphological evolution of Cu nanoparticle catalysts using a flow-through electrochemical cell. Our results show that applying high overpotentials (-0.7 V RHE to -0.9 V RHE) induces a dramatic transformation of spherical Cu nanoparticles into a distinct bundled nanowire structure. This structural rearrangement results in a nearly twofold increase in double-layer capacitance (CDL), driving a gradual rise in total current density over time. Comprehensive characterizations (SEM, XRD, XPS) reveal that this adaptive nanostructure develops via a dynamic dissolution-redeposition mechanism, uniquely enabled by the strong chemical interactions between Cu and NO or its reactive intermediate, hydroxylamine (NH2OH). Importantly, long-term stability tests up to 24 hours confirm that despite these dynamic morphological changes, the exceptional Faradaic efficiency for NH3 is robustly maintained, reaching up to 95% at -0.6 V RHE and achieving a maximum partial current density of 263 mA cm-2. This work offers critical mechanistic insights into the self-adaptive behaviors of Cu-based catalysts, providing a key foundation for designing highly efficient electrocatalysts for nitrogen upcycling.
