CO Adsorption and Oxidation on N-Doped TiO2 Nanoparticles

In order to oxidize CO to CO2 during the process of steam pyrolysis nuclear graphite waste, the adsorption and oxidation of a CO molecule on undoped and N-doped TiO2 nanoparticles has been studied by first-principles calculations, including the adsorption energies, bond lengths, local density of states (LDOSs), 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. CO2 and carbonate form during the adsorption process on the dangling oxygen atom. The CO over the undoped and N-doped nanoparticles forms CO2 by detaching the dangling oxygen atom. Less than 0.22 eV energy gained can drive the CO2 away to a distance greater than 3.01 angstrom. Therefore, the CO molecule can be oxidized to CO2 by TiO2 nanoparticle, and the physically adsorbed CO2 molecule can spontaneously dissociate at room temperature, apart from the energies released in the adsorption process. The adsorption energy for an undoped particle is -093 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.