Catalysis Research Center, Hokkaido University, North 21, West 10, Sapporo 001-0021, Japan.
Phys Chem Chem Phys. 2010 Mar 14;12(10):2344-55. doi: 10.1039/b917399d. Epub 2010 Jan 12.
Fifteen commercial titania (titanium(iv) oxide; TiO(2)) powders were modified with gold by photodeposition to prepare photocatalysts that work under irradiation with light in the visible range (vis). The gold-modified titania (Au/TiO(2)) powders were characterized by diffuse reflectance spectroscopy (DRS), field-emission scanning electron microscopy (FE-SEM), scanning transmission microscopy (STEM) and X-ray powder diffraction (XRD). It was shown that all tested powders could absorb visible light with an absorption maximum at localized surface plasmon resonance (LSPR) wavelengths (530-600 nm) and that the size and shape of gold nanoparticles determined the absorption ranges. The photocatalytic activity of Au/TiO(2) powders was examined both under ultraviolet and vis irradiation (mainly >450 nm) for acetic acid and 2-propanol photooxidation. It was found that the activity depended strongly on gold and titania properties, such as particle size and shape, surface area and crystalline form. Under vis irradiation, large rutile particles loaded with gold particles of a wide range of sizes showed the highest level of photocatalytic activity, possibly due to greater light absorption ability in a wide wavelength range resulting from transverse and longitudinal LSPR of rod-like gold particles. Action spectrum analyses showed that visible-light-induced oxidation of organic compounds by aerated gold-titania suspensions was initiated by excitation of LSPR absorption of gold. Although photocatalytic activity of nanosized gold particles under vis irradiation with a wavelength of ca. 430 nm and catalytic activity of gold-modified titania during dark reactions were also found, it was shown that the activities of Au/TiO(2) particles originated from activation of LSPR of gold by light of wavelength of 530-650 nm. Participation of molecular oxygen as an electron acceptor and titania as a conductor of electrons is suggested by comparing with results obtained under deaerated conditions and results obtained using a system containing gold-deposited silica instead of gold-titania, respectively. On the basis of these results, the mechanism of visible-light-induced oxidation of organic compounds on gold-titania is proposed.
十五种商用锐钛矿（钛（IV）氧化物；TiO2）粉末通过光沉积被金修饰，以制备在可见光（vis）照射下工作的光催化剂。金修饰的二氧化钛（Au/TiO2）粉末通过漫反射光谱（DRS）、场发射扫描电子显微镜（FE-SEM）、扫描透射显微镜（STEM）和 X 射线粉末衍射（XRD）进行了表征。结果表明，所有测试的粉末都可以吸收可见光，最大吸收位于局域表面等离子体共振（LSPR）波长（530-600nm），并且金纳米粒子的尺寸和形状决定了吸收范围。Au/TiO2 粉末的光催化活性在紫外光和可见光照射下（主要为>450nm）均进行了考察，用于乙酸和 2-丙醇的光氧化。结果发现，活性强烈依赖于金和二氧化钛的性质，例如颗粒大小和形状、表面积和晶体形式。在可见光照射下，负载大小范围广泛的金颗粒的大锐钛矿颗粒表现出最高的光催化活性，这可能是由于棒状金颗粒的横向和纵向 LSPR 导致在宽波长范围内具有更大的光吸收能力。作用光谱分析表明，含氧金-二氧化钛悬浮液中有机物的可见光诱导氧化是由金的 LSPR 吸收激发引发的。尽管还发现了在可见光波长约 430nm 下纳米金颗粒的光催化活性以及黑暗反应中金修饰的二氧化钛的催化活性，但结果表明，Au/TiO2 颗粒的活性源自波长为 530-650nm 的光对金的 LSPR 的激活。通过与脱氧条件下的结果和分别使用含有沉积金的二氧化硅代替金-二氧化钛的系统获得的结果进行比较，提出了分子氧作为电子受体和二氧化钛作为电子导体参与的建议。基于这些结果，提出了金-二氧化钛上有机化合物可见光诱导氧化的机理。
