Sustainable removal of N₂O by mediated electrocatalytic reduction at ambient temperature electro-scrubbing using...

Direct catalysis is generally proposed for nitrous oxide (N₂O) 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)₄]^3-) mediator, to enable N₂O reduction in a single process stage. The initial studies of 10 ppm N₂O absorption into 9 M KOH and an electrolyzed 9 M KOH solution showed no removal. However, 95% N₂O 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 N₂O removal was mediated by an electrocatalytic reduction (MER) pathway. Online analysis identified the reaction product to be ammonia (NH₃). Increasing the feed N₂O concentration increased NH₃ formation, which suggests that a decrease in electrolyzed solution reactivity induced by the increased N₂O load constrained the side reaction with the carrier gas. Importantly, this study outlines a new regenerable method for N₂O removal to commodity product NH₃ at ambient temperature that fosters process intensification, overcomes the limitations generally observed with catalysis, and permits product transformation to NH₃.