Reconstruction and Dissolution of Copper Catalysts during Electrocatalytic Nitrate Reduction

Copper-based electrocatalysts are widely explored for electrochemical nitrate remediation, yet their stability under operating conditions remains poorly understood. While nanoscale and subnanoscale Cu motifs are known to restructure during the nitrate reduction reaction (NO₃RR), how these transformations translate into irreversible material loss remains unclear. Here, we quantify Cu dissolution during NO₃RR as a function of catalyst architecture and electrolyte chemistry using two model systems: single-atom Cu (Cu₁) and Cu nanoparticles (Cu_NP). Time-resolved leaching measurements, integrated with in situ X-ray absorption spectroscopy (XAS), reveal measurable Cu loss for both catalysts during NO₃RR. Dissolution is concentrated at the initiation of electrolysis, coinciding with rapid restructuring, and depends strongly on morphology, with Cu_NP consistently exhibiting greater Cu loss than Cu₁. In situ XAS reveals that Cu₁ forms transient metallic clusters under reduction that largely redisperse upon returning to open-circuit voltage, whereas Cu_NP undergoes reduction of an oxidized surface layer accompanied by sustained Cu loss during electrolysis. Notably, the presence of nitrate significantly intensifies restructuring and Cu loss, highlighting the critical role of electrolyte composition. These findings establish a direct link between electrochemical restructuring and Cu dissolution, unveiling electrolyte-dependent interactions as key determinants of catalyst durability in electrochemical nitrate conversion.