Unveiling the role of microwave induction on V2O5@AC catalysts with enhanced activity for low temperature NH3-SCR reaction: an experimental and DFT study

Abstract

Supported V₂O₅@AC catalysts synthesized under microwave assistance were applied for selective catalytic reduction of NO by NH₃ (NH₃-SCR). The activity evaluation demonstrated that introducing microwaves during the impregnation could significantly improve the deNO_x performance of V₂O₅@AC catalysts, of which 3V₂O₅@AC-300 achieves the highest deNO_x activity at low temperature. Several comprehensive characterization methods including SEM, H₂-TPR, Raman, EPR, and XPS manifested that microwaves induce the high dispersion of V₂O₅ species and more exposed active sites. Additionally, 3V₂O₅@AC-300 exhibits excellent redox properties and abundant surface chemisorbed oxygen species, which may be due to the strong coupling interaction induced by microwaves between activated carbon and vanadium species, thereby creating more coordination-unsaturated V species and defects. DFT calculations further verified that oxygen vacancy doping could greatly promote the adsorption and activation of reactants, which is beneficial to SCR activity. Moreover, 3V₂O₅@AC-300 possesses a larger adsorption capacity for NH₃ than 3V₂O₅@AC, indicating that microwave irradiation could effectively modulate the adsorption sites of reactants on catalysts, especially Lewis acid sites. In situ DRIFTS results revealed a high amount of adsorbed NO₂ and monodentate nitrate species, due to abundant oxygen vacancies, were formed in 3V₂O₅@AC-300, leading to the acceleration of the SCR process.