CO Adsorption and Oxidation on N-Doped TiO₂ Nanoparticles

In order to oxidize CO to CO 2 during the process of steam pyrolysis nuclear graphite waste, the adsorption and oxidation of a CO molecule on undoped and N-doped TiO 2 nanoparticles has been studied by first-principles calculations, including the adsorption energies, bond lengths, local density of states (LDOS s ), and the charge density difference (CDD). In the adsorption process, two electrons transfer from CO to the particle resulting in the reduction of the Ti sites. CO 2 and carbonate form during the adsorption process on the dangling oxygen atom. The CO over the undoped and N-doped nanoparticles forms CO 2 by detaching the dangling oxygen atom. Less than 0.22 eV energy gained can drive the CO 2 away to a distance greater than 3.01 Å. Therefore, the CO molecule can be oxidized to CO 2 by TiO 2 nanoparticle, and the physically adsorbed CO 2 molecule can spontaneously dissociate at room temperature, apart from the energies released in the adsorption process. The adsorption energy for an undoped particle is −0.93 eV, while that for an N-doped particle is −2.47 eV or −2.52 eV. N-doped nanoparticles have stronger oxidation ability. The doped nitrogen site (N site) in N-doped nanoparticles is also a chemical adsorption site. N-doped anatase (101) surfaces have stronger adsorption ability than the undoped surface, but weaker than the N-doped anatase nanoparticles adsorption. The results show that the N-doped anatase particles can react with CO molecule more efficiently.