Particle Size-Dependent Trap States of Photoexcited Carriers in Anatase TiO2 Nanoparticles
Particle Size-Dependent Trap States of Photoexcited Carriers in Anatase TiO2 Nanoparticles
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锐钛矿型 TiO2 纳米粒子中光激发载流子的粒径依赖性陷阱状态
DOI：
10.1021/acs.jpcc.2c08125
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Akira Yamakata
中科院分区：
文献类型：
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作者：
Shimpei Naniwa;Kosaku Kato;Akira Yamamoto;Hisao Yoshida;Akira Yamakata
多相光催化是一种很有前景的人工光合作用和环境修复技术。高效光催化剂的开发需要更好地了解光激发载流子的陷阱态，因为它决定了载流子的反应性。尽管表面形貌以及表面原子的配位环境应取决于光催化剂纳米颗粒的尺寸，但陷阱状态如何随颗粒尺寸变化仍不清楚。在这里，我们发现锐钛矿型 TiO2 颗粒上的电子陷阱深度随着颗粒尺寸的增加而减小。结果表明，大多数光激发电子被深深地捕获在超细纳米颗粒（6.3 nm）的中带隙状态（距离导带最小值 3.1 至 0.7 eV），但当通过退火将颗粒尺寸增加到 14.5 nm 时，部分电子以自由电子的形式保留在导带中。进一步增加到 28.6 nm 仅显示自由电子。这些结果表明，颗粒尺寸的增加降低了深电子陷阱的密度，使得光生电子即使在微秒区域也能存活而不会被捕获。我们的结果表明，粒径是锐钛矿型 TiO2 纳米粒子中光激发载流子陷阱状态的决定因素。
Heterogeneous photocatalysis is a promising technology for artificial photosynthesis and environmental remediation. The development of efficient photocatalysts requires a better understanding of trap states of photoexcited carriers since it determines the reactivity of the carriers. Although the surface morphology as well as coordination environment of surface atoms should depend on the size of photocatalyst nanoparticles, how the trap states change with the particle size remains unclear. Here we found that the depth of electron traps on anatase TiO2particles decreases with increasing their particle size. It was shown that most photoexcited electrons are deeply trapped in the midgap states (3.1 to 0.7 eV from the conduction band minimum) in ultrafine nanoparticles (6.3 nm), but a part of electrons survived as free electrons in the conduction band when particle size was increased to 14.5 nm by annealing. Further increase to 28.6 nm exhibits only free electrons. These results show that an increase in the particle size decrease the density of deep electron traps, allowing photoexcited electrons to survive without being trapped even in the microsecond region. Our results identify particle size as a determining factor of trap states of photoexcited carriers in anatase TiO2nanoparticles.