TiO 2 nanocrystals containing oxygen defects were successfully prepared by a hydrothermal method with reductive sintering in a 5% H 2 + 95% Ar mixed atmosphere. The high-resolution transmission electron microscopy and X-ray diffraction results showed that the prepared samples were all anatase TiO 2 . X-ray photoelectron spectroscopy analysis showed that the reductive sintering converted Ti 4+ to Ti 3+ . The Ti 3+ /Ti 4+ molar ratio of the TiO 2 nanocrystals increased with increasing sintering time. The results of the electron paramagnetic resonance spectroscopy analysis showed that the reduced and sintered TiO 2 nanocrystals produced strong signals at g = 2.0010 and 1.9478, corresponding to the presence of oxygen defects and Ti 3+ , respectively. Furthermore, stronger signals were generated with increasing sintering time, indicating a progressively higher concentration of oxygen defects. The TiO 2 nanocrystalswere used as anode materials for lithium-ion batteries. One sample, H-TiO 2 -5, containing a moderate concentration of oxygen defects, presented a higher lithium ion diffusion coefficient ( D = 5.1 × 10 -13 cm 2 s −1 ) compared to the other TiO 2 samples. This sample had a Ti 3+ /Ti 4+ molar ratio of 0.179 and excellent cycling stability after 100 cycles. The discharge capacity was 124 mAh.g −1 after 500 cycles at a current density of 1C, which means that it has good cyclic stability.
The ultrafine TiO 2 nanoparticles are encapsulated in SiO 2 nanospheres by StÖber method to form (SiO x /TiO 2 )@CN composite combined with TiO 2 crystalline transformation and carbon coating process. TiO 2 nanocrystals uniformly embedded in SiO 2 nanospheres to construct a conductivity network that accelerates lithium-ions diffusion, broadens the activation range, and releases the compressive stress induced by volume change. The uniform incorporation of nitrogen elements in the homogeneous surface carbon layer can further enhance the electrical conductivity of the composite. The synergistic combination of the above advantages can work together to endow (SiO x /TiO 2 )@CN with outstanding structural stability, high specific cycle capacity and excellent rate performance. The mass discharge capacity of M5@CN is stable at 547 mA h g − 1 after 500 cycles at 1.0 A g − 1 . The specific capacities of mass discharge at 0.2, 0.5, 1.0, 2.0, and 5.0 A g − 1 are 604, 577, 496, 375, 216 mA h g − 1 , respectively. This research provides a significant reference point for future modifications of SiO 2 -based anode materials.
To reveal the ways and causes of conversion efficiency enhancement for quantum dot-sensitized solar cells (QDSSCs), chalcopyrite structure CuInS 2 quantum dots (QDs) was synthesized in oil phase by the high temperature hot injection method. Then, QDs were transferred from oil phase to water phase with 3-mercaptopropionic acid as a ligand exchange reagent and loaded inducer of QDs. 3-mercaptopropionic acid coated QDs in water phase were sensitized on TiO 2 nanocrystalline thin films to fabricate QDSSCs. The sensitization time of QDs and pH value in QDs solution are two important factors to affect the loading amounts of QDs and performance of the final assembled QDSSCs. Long-time sensitization of QDs on the TiO 2 porous thin film will cause QDs to agglomerate and stack on the film. The pH of QDs aqueous solution influences the stable existence in solution of QDs and adsorption on the surface of TiO 2 . By balancing the influence of the above two factors, the optimal sensitization condition of CuInS 2 QDs is adsorption in pH = 11 QDs solution for 2 h. In addition, the interface between QD-sensitized TiO 2 porous thin film and FTO is another factor to affect the photoelectric conversion efficiency of QDSSCs. By adding Zn-doped TiO 2 compact layer with high conductivity and electron mobility on QDSSCs to modify this interface, the photoelectric conversion efficiency of QDSSCs was further increased by 66.4 %.
危险品化学品经营许可证（带存储）