Anion leaching induced amorphous Cu/CuOx on N-doped carbon for efficient electrochemical nitrate reduction to ammonia

Abstract

The electrochemical valorization of nitrate-containing industrial wastewater into green ammonia (NH₃) presents a carbon-neutral pathway for simultaneously addressing environmental remediation and sustainable chemical production. Copper-based catalysts exhibit inherent advantages in the nitrate reduction reaction (NtRR) due to their optimal d-band electronic structure for *NO₃⁻ adsorption/activation. However, their performance is fundamentally constrained by insufficient active site density. Herein, we propose an anion leaching-driven dynamic reconstruction strategy to engineer self-optimizing Cu/CuO_x heterostructured catalysts through chronoamperometric activation of CuCl-decorated nitrogen-doped carbon black (CuCl-N/CB). Spectroscopic characterization studies reveal that potential-induced Cl⁻ leaching triggers structural reconstruction, creating abundant dual-active Cu⁰–Cu⁺ sites for the NtRR. The resulting amorphous Cu/CuO_x-N/CB reveals the highest NH₃ yield rate of 6.94 mg cm⁻² h⁻¹ with a faradaic efficiency (FE) of 92.4% at −0.76 V vs. RHE, which are 1.20 and 1.21 times higher than those of the directly prepared Cu-N/CB catalyst in terms of NH₃ yield rate and FE, respectively. Scaling to proton-exchange membrane (PEM) electrolyzers demonstrates industrial relevance, delivering 68.11 mg h⁻¹ NH₃ production at 96.8% FE under 88.7 mA cm⁻². This work provides an effective strategy to prepare Cu-based catalysts from CuX (X = Cl, Br, or I), which show high activity and NH₃ selectivity in the NtRR.