Chemometrics-boosted protocols for effortless evaluation of factors affecting the electrochemical nitrate reduction to ammonia

Abstract

Food production demand is constantly growing, entailing a proportional increment in fertilisers and pharmaceuticals use, which are eventually introduced to the environment, leading, among others, to an imbalance in the nitrogen cycle. Electrochemical nitrate reduction reaction is a delocalised route for nitrates elimination and green ammonia production. In the present study, we carry out nitrates electroreduction over a commercial MoS₂ catalyst, focusing on optimising selected input factors affecting the reaction. Concretely, Doehlert design of experiment and response surface methodology are employed to find the proper combination of supporting salt concentration in the electrolyte, applied potential, and catalyst loading at the working electrode, with the overall aim to boost Faradaic efficiency (FE) and ammonia production. As a matter of fact, varying these input factors, the obtained FE values ranged from ∼2% to ∼80%, highlighting the strength of the newly conceived approach. Moreover, our multivariate strategy allows the quantification of each factor effect and elucidates hidden interactions between them. Finally, successful extended durability tests are performed for 100 h at both FE and productivity (P) optimal conditions. In parallel, cell electrodes are characterised by in-depth structural, morphological, and surface techniques, before and after ageing, overall demonstrating the outstanding stability of the proposed electrochemical reactor.