Seto Sugianto Prabowo Rahardjo, Yu-Jen Shih, Zhi-Lun Wu
Electrochemical ammonia oxidation reaction (EAOR) has emerged as an effective method for treating water containing low NH3 concentrations. Unlike energy-oriented systems, where oxidation often targets power generation, the selectivity conversion of ammonia to non-toxic nitrogen (N2) remains a major challenge in complex wastewater matrices. In this study, a series of noble metals were plated onto copper crystals (M-Cu, M = Ru, Rh, Pd, Pt, Ag) aimed at mitigating Cu passivation, thereby enhancing the EAOR performance. The Cu sublayer effectively initiated NH3 adsorption and dehydrogenation at 0 V (vs. RHE), while the surface M metals improved the electrochemically active surface area, corrosion resistance, and catalytic stability of copper. Among M-Cu electrodes, PtCu and AgCu achieved nearly complete ammonia removal with high N2 selectivity (> 80%) at + 1.0 V (vs. RHE) and pH 11, and AgCu obtained the lowest energy consumption. Mechanistic analyses revealed that the strong affinity of OH- to the neighboring M sites lowered the activation barrier for NHx dehydrogenation mediated by the reversible Cu2O/CuO redox couple, followed by dimerization to N2. The treatability of an optoelectronic wastewater (250 mg-N L−1) was further demonstrated via constant-current electrolysis (2 mA cm−2) using the M-Cu electrodes and a steady-state kinetic model was established to evaluate the mechanistic insights of the EAOR process. © 2026 Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Department of Aquaculture, Faculty of Fisheries and Marine Science, Universitas Brawijaya, East Java, Indonesia; Institute of Environmental Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan; Brawijaya University, Indonesia
