Thermally activated epoxy-functionalized carbon as an electrocatalyst for efficient NOx reduction

Abstract

Large toxic emissions like nitrogen and sulphur oxides (NOx, SO2) are causing serious environmental and health issues. Catalytic reduction of NOx and SOx into friendly gases is considered one of the best approaches. However, regeneration of catalyst, higher bond-dissociation energy for NOx,i.e., 150.7 kcal/mol, escape of intermediate gas (N2O, a greenhouse gas) with treated flue-gas, and limited activity of catalyst remains a great challenge. Here, a cheap, binderless naturally-extracted bass-wood thin carbon electrode (TCE) was fabricated, which shows excellent catalytic activity towards NOx reduction. The bass-wood carbonization was carried out at 900 °C followed by thermal activation in the presence of CO2 gas at 750 °C. The thermal activation resulted in increased epoxy groups on the surface of the TCE and enhancement in the surface area as well as the degree of graphitization. The TCE unique 3D strongly inter-connected network through hierarchical micro/meso/macro pores that allow large electrode/electrolyte interface. Owing to these characteristics, the TCE exhibited excellent catalytic efficiency towards NOx (∼83.3%) under ambient conditions and enhanced catalytic response around neutral pH and sulphite exposure as well as excellent stability up to 168 h. Moreover, a temperature-dependent activity trend was found where the highest catalytic activity was achieved at 80 °C beyond which the electrolyte became evaporative and resulted in performance decrease. The designed electrocatalyst is low-cost, sustainable and showed great potential for effective NOx-reduction, which might be used for NOx abatement at large scale..