Hydrothermal N-doped TiO2: Explaining photocatalytic properties by electronic and magnetic identification of N active sites
Hydrothermal N-doped TiO2: Explaining photocatalytic properties by electronic and magnetic identification of N active sites
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DOI：
10.1016/j.apcatb.2009.09.024
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发表时间：
2009-11-25
影响因子：
22.1
通讯作者：
Morazzoni, Franca
中科院分区：
文献类型：
--
作者：
D'Arienzo, Massimiliano;Scotti, Roberto;Morazzoni, Franca
采用水热法成功合成了可见光范围内具有高光活性的n掺杂TiO2纳米晶体，然后在不同温度（350-600℃）下进行热退火，以使不同的氮扩散到TiO2晶格中。通过漫反射光谱、电子顺磁共振和x射线光电子能谱分析研究了TiO2的光学和磁性能，发现TiO2被有效掺杂。热处理诱导氮以氮阴离子N-的形式插入到TiO2晶格中，通过EPR检测到N-中心点，其离子性质随退火温度的变化而变化。n -中心点的数量在450℃前增加，然后减小。在可见光照射（λ > 385 nm）下，苯酚的光矿化也有类似的趋势：在450℃退火的N- tio2中，N掺杂样品的光活性达到最大值。总体结果表明，催化剂的效果取决于N-中心捕获光生空穴的能力。这种效应降低了电子-空穴复合的速率，并允许N中心点（N- + h(+)）中心作为强氧化剂。(C) 2009 Elsevier B.V.版权所有
N-doped TiO2 nanocrystals with high photoactivity in the visible range, were successfully synthesized by hydrothermal method, followed by thermal annealing at different temperatures (350-600 degrees C), in order to allow differential nitrogen diffusion into the TiO2 lattice. Optical and magnetic properties, studied by diffuse reflectance spectroscopy, electron paramagnetic resonance and X-ray photoelectron spectroscopy analysis, revealed that TiO2 was effectively doped. The thermal treatment induces insertion of nitrogen into TiO2 lattice in the form of nitride anion N-, detected as N-center dot by EPR, whose ionic character varies with the temperature of annealing. The amount of N-center dot increases till 450 degrees C, then it decreases. Similar trend was observed for the photomineralization of phenol under visible light irradiation (lambda > 385 nm): the photoactivity of N-doped samples becomes maximum for N-TiO2 annealed at 450 degrees C. The overall results suggest that the efficacy of the catalyst depends on the ability of N- centers to trap photogenerated holes. This effect lowers the rate of electron-hole recombination and allows the N-center dot (N- + h(+)) center acts as strong oxidizing agent. (C) 2009 Elsevier B.V. All rights reserved.