Volume 14, Issue 55, 2025 (July – September)
Review Article
Bio-inspired Cobalt Complexes for Homogeneous Nitrite Reduction: A Mini Review
Suman Kr Dey
Keywords: Electrocatalytic nitrite reduction, cobalt catalysts, ammonia synthesis, ligand design
DOI:10.37273/chesci.cs022056041
Full Text – PDF
Abstract
Ammonia (NH3) is one of the most indispensable feedstocks for many fertilizers/chemicals and pharmaceutical products and Haber-Bosch process is the process which makes synthetic ammonia available on an industrial scale, with most of this ammonia used for fertilizers. Despite decades of research, no milder alternative has replaced the Haber–Bosch process. Electrocatalytic reduction of nitrate and nitrite to produce ammonia offers an effective approach for fixing the artificial nitrogen cycle and replacing energy demanding Haber-Bosch process. Nitrite reduction can also help to alleviate global nitrite accumulation problems in wastewater due to anthropogenic activities, which have caused severe nitrogen unbalance and pose a threat to human health. Moreover, Nitrite reduction catalysts can function as models of nitrite reduction enzymes such as cytochrome c nitrite reductases and the siroheme-containing nitrite reductase. However, nitrite reduction is complicated by a variety of factors. Nitrite has complex aqueous phase chemistry with the formations several species like NO2−, HNO2, and NO+ depending on the acidity of the solution. Additionally, multiple thermodynamically favoured nitrite reduction products exist, many of which have similar reduction potentials, presenting a concern on selectivity of the products. Hence the mechanism of converting nitrite into ammonia warrants careful investigation. Molecular cobalt catalysts are regarded as promising systems for nitrite reduction reactions (NO2−RR). However, designing and controlling the coordination environment of molecular catalysts is crucial for studying the mechanism of NO2−RR and catalyst design. In the review, we tried to focus on cobalt based molecular electrocatalysts reported so far for homogeneous reduction of nitrite.
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