Studies On Coupling Reactions Of Molecules On Anatase TiO₂?001? Surface

Titanium dioxide(TiO2)has attracted enormous research attention for its extensive applications.In order to further improve and push the practical applications of this material,it is quite vital to study the mechanism of the interactions between TiO2 surfaces and the adsorbates.In this thesis,we study the adsorption behavior and the coupling reactions of acetaldehyde and methanol molecules on the anatase TiO2(001)-(1×4)surface by using temperature programmed desorption(TPD)technology.The main contents are shown in bellow.Chapter 1,an overview of the basic theory of TPD and the TPD spectra under various desorption orders are presented.We summarized research significance,bulk structure and electronic structure of TiO2 as well as the reconstruction and ball-stick model of anatase TiO2(001)surface.The apparatus used in experiments and the working principle of quadrupole mass spectrometer are all described.The sample preparation and the growth rate of samples are all clearly introduced.Chapter 2,it is focused on the physical-chemistry of acetaldehyde on the anatase TiO2(001)surface.The experimental results showed that acetaldehyde only desorbed in molecular form rather than reacting on the perfect lattice sites of the as-grown surface.However,the coupling reactions of acetaldehyde to form 2-butanone and butene were preferred on the reduced surface.By controlling the coverages of acetaldehyde and the surface condition of the samples,we found that the coupling reactions occurred on the oxygen vacancies of the surface.In addition,the decomposition of acetaldehyde to CO could take place on the anatase TiO2(001)surface without ultraviolet irradiation.Chapter 3,on the anatase Tio2(001)surface,we studied the coupling reactions of methanol with a large amount of exposure at 270 K.Under this condition,the couplings of methanol to form the products containing multi-carbon and desorbing from the surface around 350 K.And the products could be ·C2H5O,·C2H3O,C3H8O2 and C3H6O2.Furthermore,the formation of the products was related to the surface structure and the adsorption temperatures.We proposed a possible process of the coupling reactions of methanol.