The Mechanism And Improvement Of O₂ Adsorption On The Anatase TiO₂（101） Surface

It is the persistent research hot that improving the photocatalysis activity of titanium dioxide（TiO₂）which is a famous hetergeneous photocatalyst.The studys of its photocatalytic mechanism show that the redox reactions which happened on the surface have a great influence on its photocatalytic activity,and the first step is gas adsorption on the surface.The adsorption of O₂ is a key step,which maybe generate several key active species.The obvious features of adsorption of O₂ are electron transfer and oxygen reduction.Anatase shows a good photocatalytic property.Its stable and main exposed surface is the（101）surface,but hard to adsorb O₂.To understand this probrem,we start our research based on the truth that when O₂ adsorbed on the surface,the electrons on the surface would transfer to O₂.According to our results,a mechanism model for adsorption of O₂ was given and two improvment ways were provided.To find out the reason for O₂ hard to adsorb on anatase（101）surface,we stuied the results of O₂ adsorbing on the Fe doped TiO₂（p type）,Cr doped TiO₂（n type）,and the TiO₂ surface only with an oxygen vacanay.The results showed that only the case with an oxygen vacanay could adsorb the O₂.A further research indicates that only when the defect energy level generated by defect is close to the conduction band and occupied by electrons,the O₂ would adsorb on the surface and obtain eletrons from the surface.We optimized the calcultions,provided the mechanism and put forward an absorption model.According to model,two improvement methods were given:making oxygen vacanay on surface or introducing extraneous electron.The absorption of O₂ have been observed on the surfaces after treatment.And the adsorption energy is lower in the extraneous electron case,which may be better for desorption and dissociation of O₂.