Jiang Baojiang, Tang Yunqi, Qu Yang, Wang Jian-Qiang, Xie Ying, Tian Chungui, Zhou Wei, Fu Honggang
Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education of the People's Republic of China, Heilongjiang University, Harbin 150080, China.
Nanoscale. 2015 Mar 21;7(11):5035-45. doi: 10.1039/c5nr00032g.
Black TiO2 containing Ti(3+) attracts enormous attention due to its excellent visible-light driven photocatalytic activity. Herein, an in situ thermal decomposition approach to synthesize uniform thin carbon coated Ti(3+)-TiO2 nanocrystals is presented. During the oleic acid-assisted solvothermal process, the crystal size and morphology of TiO2 were controlled through oleic acid with carboxylic acid groups. Then the residual small quantities of oleic acid anchored on TiO2 were used as a carbon source, which could be in situ pyrolyzed into a carbon layer on TiO2 at high temperature and under an inert atmosphere. Meanwhile, Ti(4+) species were partly reduced into Ti(3+) states/oxygen vacancies on the surface of TiO2 due to the carbothermal reduction reaction for the carbon-encapsulated Ti(3+)-TiO2 structure. A series of characterizations indicated that the 20-25 nm TiO2 nanocrystals obtained were wrapped evenly by 1-2 nm carbon layers, which had an important effect on the energy band structure change of TiO2. The presence of the carbon layer also improves the Ti(3+) stability and the conduction behavior of the composites. The Ti(3+) states/oxygen vacancies created on the surface of TiO2 were responsible for the remarkable photogenerated charge separation and extended visible-light absorption range. Furthermore, Ti(3+) states/oxygen vacancies and the carbon layer together could enhance the adsorption ability of O2 so as to promote the photogenerated electrons captured by the adsorbed O2, leading to a great increase in the charge separation. As a result, the composites exhibit high photocatalytic performance for organic pollutants under visible light irradiation. This simple and new method may pave the way to practical applications for efficient photocatalytic degradation under visible light.
含Ti(3+)的黑色二氧化钛因其优异的可见光驱动光催化活性而备受关注。在此，提出了一种原位热分解方法来合成均匀的薄碳包覆Ti(3+)-TiO2纳米晶体。在油酸辅助的溶剂热过程中，通过具有羧酸基团的油酸控制TiO2的晶体尺寸和形貌。然后，将锚定在TiO2上的少量残留油酸用作碳源，其可在高温和惰性气氛下原位热解为TiO2上的碳层。同时，由于碳包覆Ti(3+)-TiO2结构的碳热还原反应，TiO2表面的Ti(4+)物种部分还原为Ti(3+)态/氧空位。一系列表征表明，所获得的20-25 nm TiO2纳米晶体被1-2 nm碳层均匀包裹，这对TiO2的能带结构变化有重要影响。碳层的存在还提高了Ti(3+)的稳定性和复合材料的导电行为。TiO2表面产生的Ti(3+)态/氧空位导致了显著的光生电荷分离和扩展的可见光吸收范围。此外，Ti(3+)态/氧空位和碳层共同作用可增强对O2的吸附能力，从而促进被吸附的O2捕获光生电子，导致电荷分离大幅增加。结果，该复合材料在可见光照射下对有机污染物表现出高光催化性能。这种简单的新方法可能为可见光下高效光催化降解的实际应用铺平道路。
