Dynamic Reconstruction of Cu Catalyst Under Electrochemical NO Reduction to NH₃

The electrochemical reduction of nitric oxide (NO) to ammonia (NH₃) offers a sustainable way of simultaneously treating the air pollutant and producing a useful chemical. Among catalyst candidates, Cu emerges as a stand-out choice for its superb NH₃ selectivity and production rate. However, a comprehensive study concerning its catalytic behavior in the NO reduction environment is still lacking. Here, we unravel the dynamic rearrangement of Cu catalysts during NO reduction: the emergence of a bundled nanowire structure dependent on the applied potential. This unique structure is closely linked to an enhancement in double-layer capacitance, leading to a progressive increase in current density from 236 mA cm⁻² by 20 % over 1 h, while maintaining a Faradaic efficiency of 95 % for NH₃. Characterizations of Cu oxidation states suggest that the nanostructure results from the dissolution-redeposition of Cu in the aqueous electrolyte, influenced by the interaction with NO or other reactive intermediates. This understanding contributes to the broader exploration of Cu-based catalysts for sustainable and efficient NH₃ synthesis from NO.