Electroreduction from Nitrite to Ammonia over Cobalt Sulfide Nanorods on Nickel

Abstract

Electrochemical nitrite reduction reaction (NO 2 RR) can meet the need to remove nitrite (NO 2 − ) pollutants and provide a sustainable way to produce ammonia (NH 3 ). However, the conversion process from NO 2 − to NH 3 is a complex multistep process involving six-electron transfer, posing a significant challenge for designing efficient catalysts for the NO 2 RR. Here, a series of cobaltbased sulfide (Co x S y ) nanorods (NRs) anchored on nickel foam (NF) with varying sulfur contents (CoS 1.035 NRs/NF, CoS 2 NRs/NF, Co 3 S 4 NRs/NF, and CoS 1.097 NRs/NF) were synthesized through phase-controlled synthesis. The optimal cobalt-based sulfide nanorods (CoS 2 NRs/NF) exhibit superior performance in the NO 2 RR, with an extremely high NO 2 − conversion rate (97.8%), Faradaic efficiency (97.9%), and NH 3 selectivity (98.7%). These results surpass those of previously reported NO 2 RR catalysts. Controlled experiments confirm that for the different cobalt sulfide phases, the higher the sulfur content, the more active hydrogen produced, which is more conducive to the electroreduction from NO 2 − to NH 3 . This research presents novel insight into the rational design of NO 2 RR catalysts.