锐钛矿(001)与(101)晶面在光催化反应中的作用

采用水热法制备了(001)和(101)晶面暴露的单晶锐钛矿TiO₂颗粒. 利用光还原沉积贵金属(Au, Ag, Pt)和光氧化沉积金属氧化物(PbO₂, MnO_x)的方法研究了暴露的锐钛矿(001)和(101)晶面在光催化中的作用. 通过透射电子显微镜(TEM)、扫描电子显微镜(STM)、能量色散X射线光谱仪(EDX)和X射线光电子能谱(XPS)的表征, 发现发生光还原反应生成的贵金属粒子主要沉积在暴露的锐钛矿(101)晶面上, 而发生光氧化反应产生的金属氧化物颗粒主要沉积在暴露的锐钛矿(001)晶面上. 此结果表明光激发产生的电子与空穴主要并分别分布在单晶锐钛矿TiO₂的(101)与(001)晶面上, 并在其上参与光催化还原反应和氧化反应. 同时也表明暴露的不同晶面对光生电荷具有分离效应. 基于本研究可以认为同时暴露分别进行氧化和还原反应的晶面可以有效促进光催化反应.

Roles of (001) and (101) Facets of Anatase TiO2 in Photocatalytic Reactions

Single crystals of anatase TiO₂ with exposed (001) and (101) facets were synthesized by a hydrothermal method. We carried out photocatalytic reduction reactions to deposit noble metals (Au, Ag, and Pt) and photocatalytic oxidation reactions to deposit metal oxides (PbO₂ and MnO_x) on the surface of TiO₂. The deposited anatase TiO₂ samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) to study the roles of the two facets of anatase TiO₂ in photocatalytic reactions. The noble metals were selectively deposited on the exposed (101) facet, while metal oxides were selectively deposited on the exposed (001) facet. This result indicated that photogenerated electrons and holes mainly accumulated on the (101) and (001) facets, and then took part in photocatalytic reduction and oxidation reactions, respectively. These results also suggested that the simultaneous exposure of the two facets could facilitate charge separation. Therefore, it was proposed that the simultaneous exposure of two facets with different functions will be a new strategy to effectively promote photocatalytic reaction.