A CoOxHy/β-NiOOH electrocatalyst for robust ammonia oxidation to nitrite and nitrate

Sam Cohen, Sam Johnston, Cuong K. Nguyen, Tam D. Nguyen, Dijon A. Hoogeveen, Daniel Van Zeil, Sarbjit Giddey, Alexandr N. Simonov, Douglas R. MacFarlane

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As the global demand for fertilisers and other nitrogenous products increases, so does the demand for robust, cost-effective and sustainable alternatives to the Ostwald process for the oxidation of ammonia to NOx compounds. Attention has turned to the electrochemical ammonia oxidation to nitrite and nitrate ([NO2/3]) - a process that could enable distributed production of these important commodity chemicals. Studies of the ammonia oxidation reaction (AOR) for the synthesis of [NO2/3] are now trending towards more selective and cheaper catalytic materials, rather than the optimisation of Pt and other known noble metal-based catalysts that are subject to poisoning and/or corrosion. Towards this goal, we describe a composite of CoOxHy and β-NiOOH on a Ni foam substrate as an electrocatalyst for the AOR that enables generation of [NO2/3] under alkaline conditions over extended periods of operation. Specifically, the average [NO2/3] yield rate of 1.5 ± 0.5 nmol s−1 cm−2 with a faradaic efficiency of 79% ± 10% is demonstrated over 4 days of continuous operation. These results represent a step forward in the development of more robust, corrosion-resistant, and industrially practical materials for the sustainable production of nitrates and nitrites.

Original languageEnglish
Pages (from-to)7157-7165
Number of pages9
JournalGreen Chemistry
Issue number18
Publication statusPublished - 21 Sept 2023

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