金红石相TiO_2纳米棒的氢化处理及其光催化活性

以钛酸四丁酯为钛源,通过盐酸调制的水热法制备出了具有棒状结构的金红石相纳米TiO2,并进一步进行高温氢化处理.采用X射线衍射(XRD),透射电镜(TEM),紫外-可见-近红外漫反射(UV-Vis-NIR DRS),电子顺磁共振(EPR)和表面光伏(SPS)等测试手段对样品进行表征,以气相乙醛和液相苯酚为目标污染物考察催化剂的光催化活性.结果表明:随着高温氢化处理时间的延长,TiO2样品的可见光吸收逐渐增强,其颜色逐渐由白色转变成灰色,这主要与引入的Ti3+/氧空位缺陷有关.表面光电压谱和羟基自由基测试表明,适当时间的氢化处理有利于光生电荷的分离.在光催化氧化降解气相乙醛和液相苯酚过程中,经适当时间氢化处理的样品表现出高的可见光催化活性.并且可见光催化活性的规律与紫外光下的是一致的.这是因为氢化处理后在导带底下方引入了缺陷能级,拓展了可见光响应.过度的氢化处理会在TiO2导带下方引入较低的缺陷能级,使光生电荷的复合加剧,导致光催化活性降低.

Hydrogenated Rutile TiO2 Nanorods and Their Photocatalytic Activity

TiO₂ rutile nanorods were successfully synthesized by a hydrochloric acid-modified hydrothermal process, using butyl titanate as the titanium source, followed by hydrogenation treatment. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-Vis near infrared (NIR) diffuse reflection spectroscopy (UV- Vis- NIR DRS), electron paramagnetic resonance (EPR), surface photovoltage spectroscopy (SPS), and the photodegradation of gas-phase acetaldehyde and liquid-phase phenol to evaluate the photocatalytic activity of the catalysts. The results show that the photoresponse of TiO₂ gradually expands from the ultraviolet region to the visible and near-infrared regions upon increasing the hydrogenation time at high temperature. Its color changed from white to gray, and this is attributed to the introduction of Ti³⁺ defects and oxygen vacancies. Based on surface photovoltage spectroscopy responses and the amount of hydroxyl radicals produced, hydrogenation treatment promoted the photogenerated charge separation significantly. This is responsible for the improved photocatalytic degradation activity toward gasphase acetaldehyde and liquid-phase phenol under visible or ultraviolet irradiation. Therefore, a specific amount of defects and/or vacancies can induce new and appropriate surface states below the conduction band of the TiO₂ samples. However, if the amount of introduced defects or vacancies is too high, low-level surface states are produced and this is not favorable for photogenerated charge separation, and detrimental to photocatalytic reactions.