Mechanism on the effect of sodium on the heterogeneous reduction reaction of NO by Char(N)

[Display omitted] •The reaction energy barrier was reduced when doped with Na.•Char(N)–NO on the surface of the armchair was easier to occur than that of the zigzag one.•The heterogeneous reduction was a unidirectional reaction that proceeds spontaneously at high temperatures. Sodium in high alkali coal promotes the heterogeneous reduction of NO in nitrogen-containing char. In order to deeply understand the mechanism of the effect of sodium on the reaction, two edge models, armchair and zigzag were employed to investigate the reaction paths before and after sodium doping, based on density function theory. It was found that after the addition of sodium, the reaction energy barriers were lowered and the exotherm of the reaction was increased, thereby the reaction was promoted. Four reaction pathways were obtained, the order of reaction difficulty is as follows: armchair@Na > armchair > zigzag@Na > zigzag. Thermodynamic analysis showed that four reactions were unidirectional reactions proceeding spontaneously. Kinetic analysis showed that the involvement of sodium the reaction rate constant was increased. Therefore, an in-depth study of the mechanism of the effect of sodium on the heterogeneous reduction of NO with nitrogen-containing char is important for promoting the clean utilization of coal and developing new carbon-based materials for detecting and removal of NO.