A DFT Study Of NO_x Adsorption On Intrinsic And Modified LaFeO₃（010） Surface

The adsorption of NO_x on the solid surface is the key to catalytic reduction.In this paper,the density functional theory method was used to study the adsorption behaviors of single NO and NO₂ on the intrinsic LaFeO₃（010）surface,meanwhile,the effects of B-site ions(B=Ni²⁺,Cu²⁺,Zn²⁺)doping and oxygen vacancy defects on the adsorption performance was explored.The best adsorption model was LaFe_1-xNi_xO_3-δ（010）surface,and the co-adsorption of NO and NO₂ on the surface of LaFe_1-xNi_xO_3-δ（010）was further studied.Get the lowest energy structure by optimizing adsorption systems,further analysis of the adsorption energy,structural parameters,Millikan population,electron density,electron density difference and density of states to obtain the optimal point and mechanism of surface adsorption.The DFT calculation results of NO adsorption on the intrinsic LaFeO₃（010）surface show that the best site for NO adsorption on the surface is the Fe atom.After adsorption,the atomic charges of the adsorption system were redistributed,and a Fe-N covalent bond is formed between NO and LaFeO₃（010）surface.The density of states show that the adsorption mechanism is a hybrid reaction between the Fe atom 3d orbit and the N atom 2p orbit.In the B-site ions(B=Ni²⁺,Cu²⁺,Zn²⁺)doped LaFeO₃（010）surface,NO adsorbed at the Ni atom on the surface of Ni²⁺doped LaFeO₃（010）.The presence of oxygen vacancy changed the surface structure and atomic charges distribution of LaFeO₃（010）.However,the calculation results show that the oxygen vacancy have no significant effect on the NO molecule adsorption.The Fe site on the intrinsic LaFeO₃（010）surface is also the best site for NO₂ adsorption.During the adsorption process,electrons are transferred from the LaFeO₃（010）surface to NO₂ molecules,and NO₂ is an electron acceptor.After adsorption reaction,a Fe-N covalent bond is formed between the surface of NO₂ and LaFeO₃（010）,and the bonding mechanism was the hybridization between the N atom 2p orbit and the 3d Fe atom orbit.Ni²⁺,Cu²⁺,and Zn²⁺doping can enhance the adsorption of NO₂ on the LaFeO₃（010）surface,and NO₂preferentially adsorbs on the Ni site on the LaFe_1-xNi_xO₃（010）surface to form stable adsorption.The presence of oxygen vacancy enhances the adsorption performance of NO₂on the LaFeO₃（010）surface,and NO₂ tends to adsorb on Fe atoms near the oxygen vacancy on the LaFeO₃（010）surface.When NO and NO₂ are adsorbed together on the LaFe_1-xNi_xO_3-δ（010）surface,the optimal configuration is that NO is adsorbed on Fe atoms near oxygen vacancy and NO₂ is adsorbed on Ni atom on the surface.The density of states results show that the adsorption of NO and NO₂ on the LaFe_1-xNi_xO_3-δ（010）surface are chemisorption,and the LaFe_1-xNi_xO_3-δ（010）surface can effectively activate NO and NO₂ molecules.The adsorption mechanism of NO_x on LaFeO₃（010）surface obtained in this paper and the method of improving the adsorption performance provide theoretical basis for the experimental design of the LaFeO₃material in the NO_x catalytic reaction.