Photocatalytic reactions are governed by photogenerated charge carriers upon band gap excitation. Therefore, for better understanding of the mechanism, the dynamics of photocarriers should be studied. One of the attractive materials is TiO₂, which has been extensively investigated in the field of photocatalysis. This review article summarizes our recent works of time-resolved visible to mid-IR absorption measurements to elucidate the difference of anatase, rutile, and brookite TiO₂ powders. The distinctive photocatalytic activities of these polymorphs are determined by the electron-trapping processes at the defects on powders. Powders are rich in defects and these defects capture photogenerated electrons. The depth of the trap is crystal phase dependent, and they are estimated to be < 0.1 eV, ∼0.4 eV and ∼0.9 eV for anatase, brookite, and rutile, respectively. Electron trapping reduces probability to meet with holes and then elongate the lifetime of holes. Therefore, it works negatively for the reaction of electrons but positively works for the reaction of holes. In the steady-state reactions, both electrons and holes should be consumed. Hence, the balance between the positive and negative effects of defects determines the distinctive photocatalytic activities of anatase, rutile, and brookite TiO₂ powders.

带隙激发后，光催化反应受光生载流子控制。因此，为了更好地理解该机理，应该研究光电载流子的动力学。有吸引力的材料之一是TiO ₂，它已经在光催化领域进行了广泛的研究。这篇综述文章总结了我们最近的时间分辨可见光到中红外吸收测量结果，以阐明锐钛矿，金红石和板钛矿TiO ₂的区别粉末。这些多晶型物的独特光催化活性由粉末上缺陷处的电子俘获过程确定。粉末中富含缺陷，这些缺陷会捕获光生电子。陷阱的深度取决于晶体的相位，对于锐钛矿，板钛矿和金红石，据估计它们分别<0.1 eV，〜0.4 eV和〜0.9 eV。电子俘获降低了与空穴相遇的可能性，然后延长了空穴的寿命。因此，它对电子的反应有负面影响，但对空穴的反应有正面影响。在稳态反应中，电子和空穴都应被消耗。因此，缺陷的正面和负面影响之间的平衡决定了锐钛矿，金红石和板钛矿TiO ₂的独特光催化活性。 粉末。