IFP Energies Nouvelles, Rond point de l'Échangeur de Solaize, BP 3, 69360 Solaize, France.
ACS Appl Mater Interfaces. 2012 Feb;4(2):752-60. doi: 10.1021/am201397n. Epub 2012 Jan 17.
Metastable TiO(2) polymorphs are more promising materials than rutile for specific applications such as photocatalysis or catalysis support. This was clearly demonstrated for the anatase phase but still under consideration for brookite, which is difficult to obtain as pure phase. Moreover, the surface doping of anatase with lanthanum ions is known to both increase the thermal stability of the metastable phase and improve its photocatalytic activity. In this study, TiO(2) nanoparticles of almost only the brookite structure were prepared by a simple sol-gel procedure in aqueous solution. The nanoparticles were then doped with lanthanum(III) ions. The thermal stability of the nanoparticles was analyzed by X-ray diffraction and kinetic models were successfully applied to quantify phases evolutions. The presence of surface-sorbed lanthanum(III) ions increased the phase stability of at least 200 °C and this temperature shift was attributed to the selective phase stabilization of metastable TiO(2) polymorphs. Moreover, the combination of the surface doping ions and the thermal treatment induces the vanishing of the secondary anatase phase, and the photocatalytic tests on the doped brookite nanoparticles demonstrated that the doping increased photocatalytic activity and that the extent depended on the duration of the sintering treatment.
介稳相 TiO2 多晶型物比金红石在某些特定应用中更有应用前景，如光催化或催化剂载体。这在锐钛矿相上已经得到了明确的证明，但在对很难获得纯相的板钛矿相上仍在考虑之中。此外，用镧离子对锐钛矿进行表面掺杂，既能提高亚稳相的热稳定性，又能提高其光催化活性。在本研究中，采用简单的水相溶胶-凝胶法制备了几乎只有板钛矿结构的 TiO2 纳米粒子。然后用镧(III)离子对纳米粒子进行掺杂。通过 X 射线衍射分析了纳米粒子的热稳定性，并成功地应用了动力学模型来定量分析相演化。表面吸附的镧(III)离子的存在将至少 200°C 的相稳定性提高了，这种温度偏移归因于亚稳 TiO2 多晶型物的选择性相稳定。此外，掺杂离子和热处理的结合导致了二次锐钛矿相的消失，掺杂板钛矿纳米粒子的光催化测试表明，掺杂提高了光催化活性，而这种程度取决于烧结处理的持续时间。
