Hydrothermal Synthesis Of Ti-Supported TiO₂ Nanotubes And The Growth Mechanism,Properties Investigation

TiO₂ nanomaterials have attracted extensive attention because of its unique properties and wide application in photovoltaic, photocatalytic, solar cells, sensors and so on. Layered titanates have been considered to be promising precursors for controllably synthesizing TiO₂ nanostructures, because the original morphology of titanates can be reserved when transformed into TiO₂ nanomaterials. It is well known that the crystal structure and morphology of the nanomaterials play critical roles in determining their fundamental properties and photoelectrochemical performance. As a result, the morphology controlled synthesis of titanate and further understanding of the formation mechanisms can play key roles in optimizing the morphologies and properties of TiO₂ nanomaterials.This work intends to clarify the different effects of sodium salts and organic solvents on the morphology of Ti-supported TiO₂ nanomaterials. Titanates were chosen as the precursor to synthesis TiO₂ nanomaterials. Titanates were prepared by hydrothermal treating Ti foils in NaOH solution under 200°C for 24 h. The as-prepared titanates were acid treated and annealed at 500 °C for 3 h in air to obtain TiO₂ nanomaterials.The main research content and results of this paper is divided into three parts:?1? The influence of organic solvents on the growth of titanate precursor. Based on our experiments, titanate nanotubes with thick tube walls?8-10 nm on one side? were obtained in alkaline aqueous solution. Organic solvents can dramatically influence the morphology and mass loading of titanate on Ti foils. Ethylene glycol can lead to the titanate nanotubes aggregating together to form network structures, while ethanol helps to produce nanosheets, which may be caused by different vapor pressure and polarity of organic solvents.?2? The influence of sodium salts on the growth of titanate precursor. Based on our experiments, the addition of NaCl can lead to the formation of titanate nanosheets, while the addition of NaF or NaBr has no obvious effect on the formation of nanosheets and nanotubes were still obtained. These ware caused by the different effects of anionic.?3? The photoelectrochemical performances of titanate-derived TiO₂ nanomaterials. Based on our experiments, TiO₂ nanosheets prepared with NaCl have the best photoelectrochemical performance compared with others, which may be caused by the different exposed facets. The increased photoelectrochemical activity of sample prepared with ethanol may be caused by the high mass loading. The sample prepared with ethylene glycol has the lowest current density, which may be caused by the collapse of the network structure and cannot accept much light for the deeper layers.This work provides basis for further study on controlling the morphology and properties of titanate as well as TiO₂ nanomaterials on Ti foils.