Studies on photocatalytic activity of monophasic and biphasic TiO₂ have been well explored. However, detailed studies on the photocatalytic activity of triphasic titania, as opposed to monophasic or biphasic TiO₂ are scarce. Here we report a comparative structure-sensitive photocatalytic study of triphasic versus anatase TiO₂, both have been synthesized under near-identical conditions through a customized sol–gel approach. The composition of the phases is tuned just by varying the thermal pre-treatment conditions of TiO₂ gel that has been subsequently subjected to calcination at 300 °C. Interestingly, when the pre-treatment temperature of the gel is systematically increased from 50 to 250 °C, a transition from anatase to triphasic (anatase, rutile, and brookite) and then again to anatase has been observed. The synthesized TiO₂ phase compositions have been thoroughly characterized for their structural, optical, electrical, surface and morphological properties. Among the different phase compositions, triphasic titania having a significant proportion of rutile has been found to exhibit the highest photocatalytic activity, as probed using model organic pollutants, Methylene Blue (MB) and 4-Chlorophenol (4-CP). In addition to the earlier known factors such as effective heterojunction, and favorable position of the valence band (VB), an important contribution to the high photocatalytic activity of triphasic TiO₂ has been experimentally found to stem from the additional electron density in VB that is attributed to the lattice contraction of anatase phase owing to the coexistence of other two phases. The study provides fundamental insights into the energetics that impact the photocatalytic activity of triphasic versus anatase TiO₂.

已经对单相和双相TiO _2的光催化活性进行了深入研究。然而，与单相或双相TiO ₂相比，关于三氧化钛的光催化活性的详细研究很少。在这里，我们报告了三相和锐钛矿型TiO _2的结构敏感的光催化比较研究，两者都是通过定制的溶胶-凝胶方法在接近相同的条件下合成的。仅通过改变TiO ₂的热预处理条件即可调整相的组成凝胶，随后在300°C下进行煅烧。有趣的是，当凝胶的预处理温度从50°C升高到250°C时，已经观察到从锐钛矿到三相（锐钛矿，金红石和板钛矿）的转变，然后又再次转变为锐钛矿。合成TiO ₂相组合物的结构，光学，电学，表面和形态学特性已得到充分表征。在不同的相组成中，已发现使用模型有机污染物亚甲基蓝（MB）和4-氯苯酚（4-CP）探测到的具有显着金红石比例的三氧化钛具有最高的光催化活性。除了较早的已知因素（例如有效的异质结和价带（VB）的有利位置）外，对三相TiO ₂的高光催化活性也有重要贡献在实验上已经发现，由于其他两相的共存，VB的附加电子密度可归因于锐钛矿相的晶格收缩。该研究为影响三相和锐钛矿型TiO ₂的光催化活性的能量学提供了基本见识。