Sustainable removal of NO by mediated electrocatalytic reduction at ambient temperature electro-scrubbing using electrogenerated Ni(I) electron mediator.

Direct catalysis is generally proposed for nitrous oxide (NO) abatement but catalysis is expensive, requires high temperatures, and suffers from media fouling, which limits its lifetime. In the present study, an ambient temperature electroscrubbing method was developed, coupling wet-scrubbing with an electrogenerated Ni(I) ([Ni(I)(CN)]) mediator, to enable NO reduction in a single process stage. The initial studies of 10 ppm NO absorption into 9 M KOH and an electrolyzed 9 M KOH solution showed no removal. However, 95% NO removal was identified through the addition of Ni(I) to an electrolyzed 9 M KOH. A change in the oxidation/reduction potential from -850 mV to -650 mV occurred following a decrease in Ni(I) concentration from 4.6 mM to 4.0 mM, which confirmed that NO removal was mediated by an electrocatalytic reduction (MER) pathway. Online analysis identified the reaction product to be ammonia (NH). Increasing the feed NO concentration increased NH formation, which suggests that a decrease in electrolyzed solution reactivity induced by the increased NO load constrained the side reaction with the carrier gas. Importantly, this study outlines a new regenerable method for NO removal to commodity product NH at ambient temperature that fosters process intensification, overcomes the limitations generally observed with catalysis, and permits product transformation to NH.