Density functional theory study on the interactions between H4POx (X = 6,7,8) groups and F,Si-doped reduced CeO1.979(111) surfaces

Abstract

The structure of F,Si-doped reduced CeO1.979(111) surfaces were studied using DFT+U method, and the interaction between F,Si-doped CeO1.979(111) surfaces and H4POx (X = 6,7,8) groups on KDP surfaces was studied. The adsorption potential energy surface, bonding structure and electronic structure of stable adsorption of H4POx groups in the interaction systems were calculated and analyzed. The results indicate that the oxygen vacancy formation energy on the Ce0.979Si0.021O1.979(111) surface decreases by 1.396 eV, while on the CeO1.958F0.021(111) surface increases by 0.271 eV. The most stable adsorption sites of H4PO6, H4PO7, and H4PO8 groups have changed to the Cebri, Ot, and Ot sites on reduced surfaces. Two Si-O bonds and two Ce-O bonds on Ce0.979Si0.021O1.979(111) surface are broken to form a cavity. The number of Ce-O(H4POx) bonds and H bonds between Ce0.979Si0.021O1.979(111) surface and H4POx groups decreases by one. The number of Ce-O(H4POx) bonds and H bonds between the CeO1.958F0.021(111) surface and H4POx groups is still 3 and 2, but the bonding length is shortened. After the interaction between three reduced surfaces and H4POx groups, the band gaps all narrow and exhibit semi-metal properties. There was no charge transfer between Si and O(H4POx) in Si-doped system, while Bader charge transfer between O(H4POx) and Ce increase in F-doped system. The density of states of Ce0.979Si0.021O1.979(111) and CeO1.958F0.021(111) surfaces with H4POx groups move towards lower energy levels, and the latter moves more and is more stable.