Electro-oxidation has attracted attention in the removal of ammonia because of its high efficiency and less chemical by-product. This study synthesized an AgO/Ag2O loaded on nickel foam electrode for NH3 oxidation, which the N2 selectivity could be improved by an asymmetric cell. The AgO/Ni anode was electroplated under 3 V for 5 min on Ni Foam, followed by calcination at 400 oC for one hour. On the other hand, the Cu/Ni cathode was prepared with the addition of benzethonium chloride. The crystal structure, micromorphology, chemical state, and composition of the surface composition were characterized by XRD, SEM, EDS, and XPS. Batch constant current experiments were carried out to assess the performance of AgO/Ni paired to Cu/Ni electrodes. The voltammetry showed that NH3 was irreversibly oxidized via dehydrogenation by electron transfer between chemical phases of AgO/Ag2O and NiOOH/Ni(OH)2. AgO/Ni was effective in NH3 removal (R = 100%, initial NH3 = 50 mg L-1), and pairing the active cathode of Cu/Ni improved the N2 up to 76%. A steady-state kinetic, which concluded a rate-limiting step of surface adsorption, explained the reaction pathways of NH3 conversion to nitrogen compounds.

Improvement in N2 selectivity of direct electrochemical ammonia oxidation by asymmetric cells composed of AgO/Ni anode and Cu/Ni cathode

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