Na助剂调控Fe(111)表面上CO2加氢制低碳烯烃反应路径及产物相对选择性的理论研究OA

Fe-based catalysts,owing to the low cost and excellent catalytic performance,are widely used in CO2 hydrogenation to light olefins.Na can significantly increase the selectivity of light olefins,but the underlying mechanism remains unclear.The influence of Na as a promoter on the reaction pathways and product relative selectivities of CO2 hydrogenation to light olefins on the Fe(111)surface was studied by combining density functional theory(DFT)calculations and microkinetic modeling(MKM)analysis.DFT calculations show that Na doping modifies the electron density of the Fe(111)surface and significantly promotes CO2 adsorption and activation.Moreover,Na reduces the energy barriers of C2H4* formation and desorption from 0.81 eV and 1.10 eV to 0.61 eV and 0.46 eV,respectively,and increase the energy barrier of CH4 formation from 0.95 eV to 1.15 eV.MKM analysis shows that Na doping substantially increases the rates of C2H4* formation and desorption and reduces the rate of CH4 formation.The rate-determining step of the entire reaction network shifts from C2H4* formation and desorption to CH4 formation.The above results reveal the intrinsic mechanism that Na increases the rates of C2H4 formation and reduces the rates of byproduct CH4 formation to increase the C2H4 relative selectivity by regulating electronic structures of the Fe(111)surface at the molecular level.