A MECHANISTIC STUDY OF THE INTERACTION AMONG C, N AND Ti_3O_s(100) SURFACE BASED ON DENSITY FUNCTIONAL THEORY

摘要

The mechanism on the interaction among C, N and Ti_3O_5(100) surface in the process of Ti(C,N) formation has been investigated using the density functional theory (DFT). The results revealed that there are three stages in the reaction process: oxygen vacancy generation, competition of C and N adsorption onto the oxygen vacancy site, and the internal diffusion of O, C and N. In the first step, C is favorably adsorbed onto the three top O sites of the Ti_3O_5( 100) surface to form CO, the oxygen vacancy could be generated after the CO dissociates from the surface. In the second step, C and N are competitively adsorbed onto the oxygen vacancy sites, the adsorption energy for N is larger than that for C. In the third step, internal diffusion of O, C and N takes place in the Ti_3O_5(100). The barrier for C to diffuse into the Ti_3O_5(100) is estimated to be 0.38eV, which is lower than that for N and O. The results suggest that internal diffusion of O in the Ti_3O_5(100) is controlling the formation of Ti(C,N).