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贵金属修饰的TiO2空心纳米光催化材料由于具有大的比表面积、低的质量密度、良好的表面渗透性、强的光吸收能力以及界面电荷的快速转移,因而表现出优异的光催化性能.为了制备结构可控且精良的贵金属修饰TiO2空心纳米光催化材料,人们先后采用湿化学法、高温固相法、声化学法及光化学沉积法等.由于在制备过程中涉及多种异相材料的合成和结构控制,因此上述合成方法通常需要复杂且多步过程(有些过程甚至很容易导致结构破坏),从而限制了其在光催化领域的实际应用.本文开发了一种简单的模板诱导法,成功制备了Ag纳米粒子修饰的TiO2空心八面体光催化剂.合成过程包括模板指导沉积和原位模板溶解.以Ag2O八面体为模板, TiF4水溶液为前驱体,首先通过TiF4水解形成TiO2纳米粒子沉积在Ag2O模板表面,而TiF4水解产生的酸性HF水溶液可原位溶解碱性的Ag2O模板,从而一步制得TiO2空心八面体.同时,利用Ag2O以及Ag+离子的光敏特性,在光照条件下使Ag2O和Ag+离子生成Ag纳米颗粒,直接沉积在TiO2空心八面体的内外表面,得到Ag/TiO2光催化剂.由此可见,该合成方法具有明显的步骤少的优点.扫描电镜、透射电镜、能量散射和紫外-可见光谱等表征结果表明成功制得内外Ag纳米粒子修饰的TiO2空心八面体光催化剂,其中TiO2空心八面体的壁厚约为25 nm,边长约为1μm,而修饰在其表面的Ag纳米粒子尺寸仅为5–10 nm.此外,通过控制TiF4前驱体浓度,还可制备核壳结构的Ag2O@TiO2八面体以及不同壁厚Ag修饰的TiO2空心八面体,表明该方法在Ag/TiO2形貌合成上的多样性和可控性.为了获得良好的光催化活性,对制备的Ag纳米粒子修饰的TiO2空心八面体光催化剂进行了不同温度的热处理. X射线衍射结果表明,即使在600 oC高温下,制备的Ag/TiO2空心八面体光催化剂依然能够保持原有的特殊形貌和锐钛矿TiO2晶型.该温度明显高于TiO2从锐钛矿向金红石转变的温度.这说明合成的Ag/TiO2能在保持高活性锐钛矿相的同时获得更好的结晶性.这可能是由于分散在TiO2原始晶粒周围的Ag纳米粒子能阻止其进一步长大,从而抑制了其晶型转变.不同样品光催化降解甲基橙的结果表明,经600oC高温热处理的样品表现出最高的光催化活性,相应的反应速率常数为0.11 min？1.这应得益于该光催化剂具有以下三个特点：(1) TiO2空心八面体的薄壁结构能够缩短光照条件下光生电子和空穴从内部扩散到表面的距离；(2)由于贵金属Ag纳米粒子沉积在TiO2薄壁的内外两个表面以及TiO2和Ag形成肖脱基势垒,因此在它们接触的界面上能够发生更快的界面电荷转移；(3)高温处理导致TiO2良好的晶化以及高活性锐钛矿TiO2晶型的保持.

Noble metal/titania hollow nanomaterials usually exhibit excellent photocatalytic activity because of their high specific surface area, low density, good surface permeability, strong light‐harvesting capacity, and rapid interfacial charge transfer. However, the present preparation methods usually include complicated and multistep procedures, which can cause damage to the hollow nanostruc‐tures. In this paper, a facile template‐induced synthesis, based on a template‐directed deposition and in situ template‐sacrificial dissolution, was employed to prepare Ag‐modified TiO2 (Ag/TiO2) hollow octahedra using Ag2O octahedra as templates and TiF4 as the precursor. In the synthetic strategy, the shells of TiO2 hollow octahedra were formed by coating TiO2 nanoparticles on the sur‐face of Ag2O templates based on the template‐directed deposition. Simultaneously, the Ag2O tem‐plates can be in situ removed by dissolving the Ag2O octahedral template in HF solution produced via the hydrolysis reaction of TiF4 in the reaction system. In addition, Ag nanoparticles were depos‐ited on the inside and outside surfaces of TiO2 shells by effectively using the photosensitive proper‐ties of Ag2O and Ag+ions under light irradiation, along with the formation of TiO2 hollow octahedra. The Ag/TiO2 hollow octahedra exhibited high photocatalytic activity because of their (1) short dif‐fusion distances between photogenerated electrons and holes because of the thin shells of Ag/TiO2 hollow octahedral, (2) deposition of Ag nanoparticles on the inside and outside surfaces of TiO2 shells, and (3) rapid interfacial charge transfer between TiO2 shells and Ag nanoparticles. This work may also provide new insights into preparing other Ag‐modified and hollow nanostructured photo‐catalysts.