The First Principles Study On Adsorption And Dissociation Mechanism Of Methanol On Modified Anatase TiO₂?101?Surface

Titanium dioxide(TiO2)is a periodic semiconductor material composed of Ti and O atoms.Due to its stable physical properties,high mechanical strength,long carrier application life,good biocompatibility and harmless to the environment,it has widely application prospect in many fields,such as solar cells,sensors and photocatalysis.With the demand for new energy materials,the photocatalytic decomposition of methanol by modified TiO2 has attracted extensive attention.In this thesis,the influence of Co atom doping on the electronic structure of anatase TiO2 surface with perfect and oxygen vacancy defects,and the adsorption and initial dissociation mechanism of methanol molecules on its surface were discussed based on the first principles.The research content includes the following parts:(1)The adsorption and dissociation of methanol on the perfect TiO2(101)surface doped with Co atoms were studied using the first principles.The calculation results revealed that the dissociation state of methanol is more stable than that of molecular state after doping Co atoms on the TiO2(101)surface.Meanwhile,the energy barrier of methanol dissociation is only 0.13 eV,which is significantly lower than that on the perfect TiO2(101)surface.The results showed that Co atom doping was beneficial to the initial dissociation of methanol molecules on the TiO2(101)surface.(2)The influence of Co atom doping on the surface structure and methanol adsorption and dissociation mechanism on the oxygen defective TiO2(101)were studied.After doping Co atoms,the surface oxygen vacancy(Vosur)of TiO2(101)surface was more stable than subsurface oxygen vacancy(Vosub).After adsorption of methanol molecules,Vosub migrated upward and form Vosur.The results revealed that the dissociation state of methanol is more stable than the molecular state on the oxygen vacancy TiO2(101)surface with Co atom doped.On the Vosur-TiO2(101)surface doped with 5 or 6 coordination Co atoms,the methanol overcomes the energy barrier of 0.52 eV and 0.35 eV,respectively,and the dissociated methoxyl group moves to the Vosur position.On the Co6c@Vosub-TiO2(101)surface methanol O-H was broken and the transition state energy barrier was 0.45 eV,which indicating that the presence of oxygen defect could promote the initial dissociation of methanol in the 6-coordinate Co system.