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

• Published in: Green chemistry : an international journal and green chemistry resource : GC Vol. 25; no. 18; pp. 7157 - 7165
• Main Authors: Cohen, Sam, Johnston, Sam, Nguyen, Cuong K, Nguyen, Tam D, Hoogeveen, Dijon A, Daniel Van Zeil, Giddey, Sarbjit, Simonov, Alexandr N, MacFarlane, Douglas R
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 18.09.2023
• Subjects: Ammonia; Catalysts; Chemical synthesis; Corrosion; Corrosion products; Corrosion resistance; Electrocatalysts; Electrochemistry; Fertilizers; Green chemistry; Metal foams; Nitrites; Nitrogen dioxide; Noble metals; Optimization; Ostwald ripening; Oxidation; Robustness; Substrates; Sustainable production
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/d3gc01835k

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.