Density functional theory study on the catalytic reduction of nitric oxide over the bio-char surface during biomass reburning: The influence of inherent potassium

Abstract

Active sites on char surface have been proven to be effective for nitric oxide (NO) reduction. In this work, density functional theory was used to study the catalytic reduction of NO over the zigzag char surface. Two bio-char models with or without potassium were established and the reaction paths during char-NO interaction were built. The effect of inherent potassium and active sites on NO reduction was taken into consideration. Mulliken charge results showed that the migration of electron from potassium(K) atom to carbon atom would increase the electron density on char surface, which further improved the electron-donating capacity. Orbital electron distribution and ESP results proved that char(K) was more likely to donate electron to NO than char-1 during char-NO interaction. Reaction potential energy results indicated that the bonded K atom on char surface would enhance the chemisorption of NO via electrical charge transfer and reduced energy barriers from 173.7 kJ/mole to 31.6 kJ/mole, which was consistent with the kinetic analysis results. The bonding of –O-K to carbon atoms on char surface greatly activated the NO reduction during char-NO interaction, which enhanced the adsorption and reduction of NO.