Reaction mechanism of selective catalytic reduction of NO with NH3 on Fe3O4 (111) surface: Experimental and DFT studies

•Surface lattice oxygen are the main factors to improve the catalytic efficiency.•Regulated the exposure of high SCR active crystal surface Fe3O4 catalyst.•The formation of NH2NO intermediates is rate-determining steps in catalytic cycle.•Combined with experiment and calculation, the reaction pathway of SCR was explored. Iron-based catalysts have vast potential for application prospect in selective catalytic reduction of NOx with NH3 (NH3-SCR). These catalysts offer excellent SCR activity at medium and high temperatures, N2 selectivity and environmental performance. Among these catalysts, Fe3O4 catalyst is highly active and significant in the denitration reaction due to the presence of both ferrous and ferric ions. This study utilized density functional theory (DFT) in combination with experimental measurements to investigate the reaction pathway of NH3-SCR on the Fe3O4(111) surface. The research found that the surface was favorable for the adsorption of NO molecules and followed the NO activation mechanism. Upon activation of NO at the Feoct site, it reacted with NH3 to form NH2NO, This compound then underwent decomposition into N2 and H2O. The presence of O2 on the catalyst facilitated the surface dehydrogenation reaction and completed the SCR cycle reaction. Based on the DFT results, the formation of NH2NO intermediate was the rate-determining step of SCR reaction. The Fe3O4(111) surface followed the L-H mechanism, which was in line with the experimental results. This study provided novel insights into the SCR reaction process and can be useful in developing new iron-based SCR catalysts.