Quantum chemical study of the effect of oxygen-containing functional groups on N2O adsorption on char

Abstract

This work aims to investigate the effect of oxygen-containing functional groups (OFGs) on nitrous oxide (N2O) adsorption on char based on density-functional theory (DFT) at M06-2X/6-311G(d) level using pristine and defective zigzag char models. The char model configurations were geometrically optimized and single-point energy was calculated. The adsorption energy, bond length, Mayer bond order (MBO), atomic dipole moment corrected Hirshfeld (ADCH) charges, electrostatic potential (ESP), partial density of states (PDOS) and interaction region indicator (IRI) were analyzed. Results show that the presence of OFGs has little influence on the structure of char model but increases its activity. In addition, it was found that the effect of OFGs on N2O adsorption on char surface is related to char model and adsorption configurations. Further char configurations analysis after adsorbing N2O molecules suggests that the OFGs addition can significantly affect adsorption energies by changing chemical bond length and MBO. Moreover, the ESP analysis indicates that the OFGs addition increases the overall level of ESP on char surface, leading to the formation of orbital hybridization and electrons transfer and further promoting N2O adsorption on char surface. ADCH analysis indicates that OFGs affect the active site charge and facilitate N2O adsorption. IRI analysis reveals a variety of weak interactions in the structure after the incorporation of OFGs. Therefore, this study provides a theoretical foundation for a better understanding of the heterogenous adsorption of N2O on char.