First Priciples Study On The Activity Of TiO₂-based And CeO₂-based Catalyst

TiO2-and CeO2-based catalysts are widely concerned and used. TiO2-based catalysts with a non-toxic, easy to use and stable the physical and chemical property, are widely used in the degradation of environmental organic pollutants. However, the bandgap of pure anatase TiO2is3.2eV, it only can make use of5%of sunlight. CeO2-based catalysts have unique ability for Oxygen Storage Capacity (OSC) and in rich of cerium resources. It is widely used in the three-way catalyst through a series of oxidation-reduction reaction to complete the car exhaust CO, HC and NOx and other toxic gas conversion. However, the OSC ability of CeO2and redox properties should be improved. It is sitll lack of theoretical research in the field of CO molecules adsorped on CeO2-bansed catalyst. In response to these problems, we in-vestigated photocatalytic activity in metal-nonmetal codoped TiO2systems, oxygen storage and oxygen release capacity of Mn, Fe mono-doped CeO2and the adsorption behavior of CO molecules adsorped in theCeFeO2(111) surface by the first-principles.The main contents are as follows:To solve the problem such as narrow range response and low photocatalytic reduction of TiO2, first of all, the general principles for improving photocatalycit activity of TiO2is induced through theoretical derivation and in combination of the photocatalytic mechanism of TiO2;a) using donor-acceptor codoped band engineering to modify the photocatalytic activity of TiO2;b) anions which p with higher atomic p orbital energies than that of0to a such as N, C and S to broaden the absorption range of visible lights for TiO2; Cations as donors which3d,4d and5d with higher atomic d orbital energies than that of Ti to make sure that the CBM energy level is not lowered and high electron mobility is maintained;(c) The quantitative criterion of doped system for TiO2is:the appropriate band gap should lower0.48eV, namely about2.72eV. And its CBM should raise0.24eV. Secondly, study the electronic density of states of3d,4d and5d transition metal monodoped TiO2system and drive the relationship between d orbitals of transition metal and that of Ti-3d orbital.Then, study photocatalytic activity of various metal-nonmetal codoping TiO2sytems.In order to improve the capacity of oxygen storage and oxygen release and catalytic reduction of CeO2material, in this paper, we researched the Mn and Fe mono-doped CeO2system by investigating geometry distortion and electronic structure as well as OSC. Then, we studied the affection of catalytic activity on Fe-doped CeO2(111) surface. Ultimately we studied the CO adsorption behavior of CO adsorped at different sites in CeFeO2(111) surface through adsorption energy, geometry and harder charge.As mentioned, the doped band engineering way used in research of wide band gap(WBG) semiconductor TiO2is also applies to other WBG gap semiconductor system. In this paper, theoretical results of improving catalytic activity of TiO2-based and CeO2-based catalysts by doping method provide a theoretical basis for experimental research and practical application.