Synthesis Of Novel TiO₂ Composites And Its Applications In Energy Storage And Photocatalysis

Titanium dioxide(Ti O2) has attracted great attentions due to its low cost, minimal toxicity, advanced chemical stability, excellent performance and safety. It has been used in many fields, such as lithium ion batteries and photocatalyst. As the anode materials in lithium ion batteries, Ti O2 owns excellent theoretical capacity corresponding to the insertion of one Li+ per formula unit and high structure stability. But the relatively low capacity and Li+ transportation have decreased the value of Li+ insertion(~0.6), actually. As photocatalyst, Ti O2 possesses advanced activity and stability. But it has relativity wide band gap(3.2 e V), which hinders the absorption of solar energy. So the tuning and improvement of the physicochemical properties of Ti O2 still remains a lot of room to deliberate. This article based on the reviews on the structure, synthesize and the physicochemical properties improvement of Ti O2, combined with the experiment on the Ti O2 and its composites to investigate their microstructure and physicochemical properties, promulgating the relationship between them. This study established a theoretical foundation for optimizing the lithium storage of Ti O2 and enlarging its photo response scope. The details have been listed as follow:(1) The hybrid nanostructure of one Dimensional Ti O2 nanoneedle and two Dimensional graphene sheet has been synthesized by a facile hydrothermal method. The microstructure research shows the as prepared Ti O2 nanoneedles were rutile which dispersed on the graphene sheets homogeneously, leading to higher structure stability. The electrochemical measurement of Ti O2 and its composites were investigated, Ti O2/r GO composites exhibit high initial reversible discharge capacity(427.6 m Ah g-1), high-rate discharge capacity(149 m Ah g-1,5C). At 1C after 50 cyclings, the composites still remain advanced reversible discharge capacity(190 m Ah g-1). Further studies indicate that this special structure with 1D/2D architecture would shorten the diffusion length of lithium ions and electron, leading to a faster lithium transportation and better structure stability.(2) The Ti O2/Bi2WO6 was synthesized via a hydrothermal route. It could be demonstrated from the XRD pattern that the as prepared composites was composed of anatase Ti O2 and tetragonal Bi2WO6. Futher researches indicate that the tooth-like Bi2WO6 nanosheet tightly dispersed on the Ti O2 nanobelt homogeneously. The UVvis diffusion measurement and the result of degradation pollutions(X-3B) under visibile light indicate that the as prepared Bi2WO6/Ti O2 nanobelt exhibits red shift with the absorption spectrum and excellent degradation performance under visible light(60%), even better than the initial Bi2WO6 nanosheet. Bi2WO6 owns a narrow band gap which could make use of the visual light during the photodegradation. The combination with Ti O2, would not only be good for the separation of photoelectrons and holes but also contribute to broaden the scope of light respond.(3) Si O2 and Chlorella are used as the template to form hollow Ti O2 square respectively. Characterization by XRD shows the as prepared Ti O2 were both anatase. SEM images demonstrate that the Si O2 synthesized by stober method disperses uniformed and almost has the same particle size while the Chlorella presents different particle size and irregular surface. The measurements of photodegrade methyl orange(MO) in UV light were investigated, the hollow Ti O2 squares synthesized by Si O2 as template exhibit much better photocatalytic performance. In the case of the hollow Ti O2 squares synthesized by Chlorella as template, the higher of calcining temperature, the better of the photocatalytic performances. Focusing on the hollow Ti O2 squares synthesized by Si O2, their performance varies by different times in alkali solutions. The photocatalytic performance advanced as the time extended, the time of 21 h owns the best performance, which MO could be degraded completed in 45 min. Then corresponding performance becomes variation with the much long time in alkali solutions. Combined with XRD and SEM image, the longer of the time in alkali solutions, the more percentage of Ti O2 they have. And before 21 h, the morphology is still integrity, but it starts to collapse during the following time in alkali solutions, this is why their performance differs. In order to further investigation, N2 absorption/desorption test was performed. The value of each specific surface area is in line well with the photocatalytic performance of each sample.