화학공학소재연구정보센터
Electrochimica Acta, Vol.281, 410-419, 2018
In-situ electrochemical formation of nickel oxyhydroxide (NiOOH) on metallic nickel foam electrode for the direct oxidation of ammonia in aqueous solution
A nickel foam-supported Ni(OH)(2)/NiOOH electrode, synthesized in-situ at a specific electrode over-potential, was used to study the oxidation of ammonia in aqueous solution. Results of voltammetric analysis showed the formal potential of Ni(OH)(2)/NiOOH transition at +0.6 V (vs. Hg/HgO, pH 11) at which the current profile was improved by electron transfers of NH3 in the electrolyte. Selectivity of NH3 conversion to NO3- and N-2 was evaluated by batch constant current experiments. Electrochemical parameters, including solution pH (6-12), temperature (20-40 degrees C), current density (0.2-3 mA cm(-2)), and initial NH3-N concentration (20-450 mg-L-1), that may affect ammonia oxidation toward nitrogen selectivity were studied. At constant current density of 1.5 mA cm(-2) A, ammonia removal reached 98.5% and NO3- was the major product at initial NH3-N concentration of 50 mg-L-1 in 7 h. By contrast, N-2 evolution dominated at low current density (<1 mA cm(-2)) and high initial NH3-N concentration (i.e., >100 mg-L-1). A surface steady-state approach, with NH3 deprotonation as the rate-limiting step, provided the reaction pathways of NH3 conversion to molecular nitrogen byproduct. (c) 2018 Elsevier Ltd. All rights reserved.