Studies Of Photochemistry On R-TiO₂?110? And ZnO?0001? Surface Using Temperature Programmed Desorption

As an important method for the kinetics and dynamics study of surface chemistry,Temperature Programmed Desorption(TPD)spectrum can be used to detect the chemical reaction products on surface in situ.Based on high-sensitive mass spectro-metry,we developed a surface photochemical apparatus and applied to invest the photocatalysis of small molecules on R-TiO2(110)and ZnO(0001).D2 formation from the photolysis of CD3OD on the clean and formate modified R-TiO2(110)surfaces at 266 nm has been investigated using TPD and DFT(density functional theory)methods.About 18.5%of the dissociated D atoms contribute to D2 formation on the DCOO-modified surfaces.The value is much higher than that on the clean surfaces,suggesting that surface DCOO-can enhance D2 production from CD3OD photolysis.DFT calculation suggests that the BBO-CH-O-Ti5c structure of HCOO-on the surface will reduce the barrier of the BBOv mediated recombinative H2 desorption,leading to efficient H2 production.Ethylene glycol is studied as a model of pollutant degradation and is also widely used in industry.Using TPD method,we studied the photoreaction process of ethylene glycol on Rutile TiO2(110).CH2O and CH3CHO products are identified at low temperature(<300 K).The C-C bond cleavage channel to produce CH2OTi and BBO-H dominates at very low EG coverage.The C-O bond cleavage channel to produce CH3CHO and water on the Ti5c sites dominates at high EG coverage,which may be affected by the accumulation of BBO-H atoms and steric hindrance of EG.The band structure of ZnO is similar to TiO2.We also studied thermochemistry and photochemistry of methanol on ZnO(0001).Dissociation of CH3O is much easier than CH3OH.Laser irradiation promotes the dissociation of CH3OH/CH3O to form CH2O,which will be further converted to HCOO-.Both temperature and illumination promote the desorption of CH3 from CH3O.