二氧化钛复合纳米管的管壁设计及其调控光生电荷行为的机制

The modulation of chemical composition and morphology of anodized TiO2 nanotubes is effective for achieving higher photocatalytic properties. The method of anodizing of Titanium alloy can in situ tailor the chemical composition of TiO2 nanotubes, TiO2 composite nanotubes were obtained. However, it still cannot tailor the tube morphology effectively. The method of tube wall design can tailor the tube morphology and nanotubes with double wall structure were obtained, but its ability of tailoring the chemical composition of nanotube is limited. In order to improve the photocatalytic properties of nanotubes more effectively, we think the advantages of above two methods can be integrated together, the morphology and chemical composition of nanotube can be simultaneously modulated during anodization process. Therefore, this project intends to combine the two methods together, TiO2 composite nanotubes will be prepared and their tube wall will be further designed. On the surface of various Titanium alloy (TiNi, TiW and Ti-Mo-Ni etc.), double wall TiO2 composite nanotubes will be prepared through anodization method. By comparing with single wall nanotubes, we will explore its formation mechanism and details of sintering process. With further measuring the photocatalytic properties, the modulation mechanism of tube wall morphology and chemical composition on the behavior of photo-generated charges will also be investigated. The successful implementation of this project will be beneficial for enriching the synthesis methods of photocatalytic materials, deepening understanding of the electrochemical self organization process and exploring novel nanotube materials.

阳极氧化TiO2纳米管的化学组成和形貌调控是提升其光催化性能的有效途径。钛合金阳极氧化法可原位调控纳米管化学组成，制得TiO2复合纳米管。但其尚不能有效调控纳米管的形貌。管壁设计法可调控纳米管形貌并得到具有双壁结构的纳米管，但其调控纳米管化学组成的能力有限。为更有效提升纳米管光催化性能，我们认为可汇集两种方法的特色，在阳极氧化时对纳米管形貌和化学组成同时进行调控。因此，本课题拟融合两种方法，制备TiO2复合纳米管并对其管壁进行设计。在不同钛合金（TiNi, TiW和Ti-Mo-Ni等）表面，采用阳极氧化法制备双壁TiO2复合纳米管。通过与单壁纳米管进行对比，探究其形成的详细机理和烧结的特征规律。进一步通过光催化性能测试，就纳米管管壁形貌和化学组成对其光生电荷行为的调控机制进行研究。该项目的顺利实施对丰富光催化材料的制备方法，加深对电化学自组装机理的认识，研制新型纳米管材料将起到积极作用。

二氧化钛复合纳米管阵列薄膜可采用阳极氧化法制备，纳米管管壁形貌和成分结构可在阳极氧化过程中进行设计。为得到更为优异的太阳能转化性能，管壁设计的规律及机制有待进一步研究。本课题在金属钛片、锆片、TiCr合金、Ti6Al4V合金和Ti6Al7Nb合金表面采用阳极氧化法制得了双壁纳米管阵列薄膜。形貌和成分分析结果表明：低电解质溶液水含量及高阳极氧化电压是形成双壁结构的关键；Cr元素能够促进纳米管的生长，Ti6Al4V及Ti6Al7Nb合金中a相和β相的阳极氧化行为不同；烧结过程中，纳米管中Al、V、Nb元素的存在能够抑制锐钛矿晶型向金红石晶型的转变。光催化测试结果表明：经过钛酸锶、Cr掺杂后，双壁二氧化钛纳米管阵列薄膜的光催化性能可得到进一步提高，纳米管阵列薄膜中Cr2O3、Al、V、Nb的掺杂降低了薄膜的光催化性能。此外，我们还在钛纱及泡沫钛表面制备得到二氧化钛纳米管阵列薄膜。经过电化学还原、氢化作用及碳点复合，纳米管阵列薄膜的光吸收性能得到明显提高，光热性能增强。将二氧化钛复合纳米管阵列薄膜用于光热驱动水蒸发，水蒸发速率达到了7.10 kg•m-2•h-1，光热转化效率为82.4%。