Preparation Of Modified TiO₂ Nanotube Catalyst And Its Photocatalytic Activity Of Hydregen Evolution From Water Splitting Under Visible Light

Procedures and optimized conditions were studied by microwave irradiation method for preparation of TiO2 nanotube. Based on this method, a series of CdS-TiO2 nanotube and Fe-TiO2 nanotube with different CdS or Fe content were synthesized. Their photocalytical activity was also evaluated by hydrogen production from water splitting. The crystal phase and structure were characterized by the modern techniques such as UV-Vis, TEM, XRD and XPS. The connection between catalysts structure and their photocatalytic activity was also investigated. The dissertation contents are mainly as follows:TiO2 nanotube was synthesized by microwave irradiation method. TEM images showed that the optimal craftworks of TiO2 nanotubes were synthesized when the microwave power was 300w and that the irradiation time is 120 min. The diameter of nanotube was about 5~10nm and its length were from 150nm to 200nm.CdS-TiO2 nanotube (CdS-TiO2NT) catalyst was synthesized on the basis of the microwave irradiation method. The CdS-TiO2NT showed good quality nanotube form. Through UV-Vis, visible light absorbance of CdS-TiO2NT was fewer than CdS but obviously much more than physical-mixed CdS+TiO2NT and TiO2NT. The results of hydrogen production from water splitting under visible light proved that CdS-TiO2NT had the best photocatalytic activity compared with CdS, TiO2 and CdS+TiO2. A series of CdS-TiO2NT with different CdS content (wt %) were also synthesized. The 1.96CdS-TiO2NT (CdS: wt%1.96) showed the best photocatalytic activity with a hydrogen production rate 12.90μmol/(h?g). The XRD and XPS results indicated that CdS had possibly formed certain kind of composite with TiO2 under microwave irradiation and that CdS enhanced photocatalytic activity of the catalyst.Fe-TiO2 nanoparticles (Fe-TiO2NP) with different Fe content (mols %) were synthesized by co-deposition method. The Fe-TiO2NT catalysts were synthesized by microwave irradiation method on the basis of Fe-TiO2NP. TEM and EDS images showed Fe element existed in the Fe-TiO2NT. UV-Vis spectrum showed that visible-light absorbance of Fe-TiO2NT increased as their Fe-doped content rose except for 2%Fe-TiO2NT. 2%Fe-TiO2NT has the most visible-light absorbance than other Fe-TiO2NT catalysts because of its good quality rutile phase structure proved by XRD results. The other Fe-TiO2NT catalysts were all anatase and titanate mixed phase. The test of hydrogen production from water splitting showed that the Fe-TiO2NT catalysts had no photocatalytic activity under visible light (>420nm). In full spectrum (200~1100nm), their photocatalytic activity increased as their Fe-doped content rose, but their photocatalytic activities were all less than pure TiO2NT. The XPS analysis indicated that Fe3+ replaced Ti4+ in the TiO2 crystal and became the recombination center of photo-excited electrons and holes, which reduced the life-span of photo-excited electrons and holes and reduced the possibility of photo-excited electrons getting the surface of catalyst. So the photocatalytic activity of Fe-TiO2NT was reduced.