In-situ electrochemical formation of nickel oxyhydroxide (NiOOH) on metallic nickel foam electrode for the direct oxidation of ammonia in aqueous solution

Yu Jen Shih, Yao Hui Huang, C. P. Huang

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)

Abstract

A nickel foam-supported Ni(OH)2/NiOOH electrode, synthesized in-situ at a specific electrode overpotential, 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 N2 was evaluated by batch constant current experiments. Electrochemical parameters, including solution pH (6–12), temperature (20–40 °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−2A, 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, N2 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.

Original languageEnglish
Pages (from-to)410-419
Number of pages10
JournalElectrochimica Acta
Volume281
DOIs
Publication statusPublished - 2018 Aug 10

All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)
  • Electrochemistry

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