Electron-Transfer Reaction of Oxygen Species on TiO2 Nanoparticles Induced by Sub-band-gap Illumination
Electron-Transfer Reaction of Oxygen Species on TiO2 Nanoparticles Induced by Sub-band-gap Illumination
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DOI：
10.1021/jp909678e
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发表时间：
2010-01-21
影响因子：
3.7
通讯作者：
Harima, Yutaka
中科院分区：
文献类型：
--
作者：
Komaguchi, Kenji;Maruoka, Takanori;Harima, Yutaka
通过原位电子自旋共振 (ESR) 和漫反射光谱研究了部分还原的 TiO2（金红石）纳米颗粒表面形成的分子氧物种。 O-2(-) (g(z) = 2.020) 和 Ti3+ 产生的 ESR 信号在 77 K 的可见光照射下出现，并在黑暗中升高温度后消失。亚带隙照明形成的O-2(-)和Ti3+自由基数量相等，表明过氧O-2(2-)物质与TiO2表面氧空位处相邻Ti4+离子之间存在可逆电子转移：Ti4+中心点中心点中心点O-2(2-)中心点中心点中心点Ti4+ -> Ti3+ + O-2(-)中心点 中心点 中心点 Ti4+（正向反应）。 ESR强度因长时间照射而饱和，并且吸附在氧空位位点的O-2分子的表面覆盖率被评估为1.3×10(13)位点cm(-2)。 O-2(-) 生成速率的光谱响应在 480 nm 附近呈现出宽峰，与漫反射测量观察到的吸收带一致。结果表明，TiO2 次表面层产生的F型色心吸收可见光，间接诱导表面氧空位位点从O-2(2-)到Ti4+的电子转移反应。
Molecular oxygen species formed on the surface of partially reduced TiO2 (rutile) nanoparticles have been studied by in situ electron spin resonance (ESR) and diffuse-reflectance spectroscopies. ESR signals due to O-2(-) (g(z) = 2.020) and Ti3+ appeared upon visible-light illumination at 77 K and vanished by raising the temperature in the dark. The numbers of O-2(-) and Ti3+ radicals formed by sub-band-gap illumination were equal, suggesting a reversible electron transfer between peroxo O-2(2-) species and the adjacent Ti4+ ion at an oxygen vacancy site on the TiO2 surface: Ti4+center dot center dot center dot O-2(2-)center dot center dot center dot Ti4+ -> Ti3+ + O-2(-)center dot center dot center dot Ti4+ (forward reaction). The ESR intensity was saturated by a prolonged illumination and a surface coverage of O-2 molecules adsorbed at the oxygen vacancy site was evaluated as 1.3 x 10(13) sites cm(-2). The spectral response for the generation rate of O-2(-) exhibited a broad peak, at around 480 nm, in agreement with the absorption band observed by the diffuse-reflectance measurements. It was concluded that F-type color centers generated in subsurface layers of TiO2 absorb the visible light to induce indirectly the electron-transfer reaction from O-2(2-) to Ti4+ at the surface oxygen vacancy site.