Factors affecting photocatalytic activity of visible light-responsive titanium dioxide doped with chromium ions
Factors affecting photocatalytic activity of visible light-responsive titanium dioxide doped with chromium ions
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DOI：
10.1039/c8cy01411f
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发表时间：
2018-09
影响因子：
5
通讯作者：
N. Nishiyama;Keisuke Kozasa;T. Okajima;M. Fujitsuka;T. Majima;S. Yamazaki
中科院分区：
文献类型：
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作者：
N. Nishiyama;Keisuke Kozasa;T. Okajima;M. Fujitsuka;T. Majima;S. Yamazaki
采用溶胶-凝胶法制备了掺杂Cr离子的二氧化钛（Cr - tio2），仅以水为溶剂，透析制备。在200℃下烧结的Cr - tio2，在可见光照射下，Cr掺杂量为0.68 ~ 1.3原子%时，4-氯苯酚（4-CP）降解率约为90%。当掺杂量大于1.7原子%时，300-500℃烧结的Cr-TiO2的4-CP降解率增加。x射线光电子能谱和x射线吸收近边结构测量表明，在200°C和400°C烧结的Cr - tio2样品表面只存在Cr(III)，并且在400°C烧结时，大块中的部分Cr（III）被氧化为Cr（VI）。随着体中Cr(VI)/Cr（III）比例的增加，4-CP的降解增强，表明在可见光照射下，Cr（III）在表面发生了空间分离：电子从Cr（III）被激发到TiO2的导带，然后被捕获在掺杂的Cr（VI）上，而光生成的Cr（IV）氧化4-CP。时间分辨漫反射光谱用于评价光生电子的寿命。在200℃下烧结的Cr-TiO2的光催化活性最高。这种高活性归因于氧空位的存在，它充当了电子捕获的位置。
Titanium dioxide doped with Cr ions (Cr–TiO2) was synthesized by a sol–gel method, with only water as the solvent, and dialysis. For Cr–TiO2 sintered at 200 °C, ca. 90% of 4-chlorophenol (4-CP) was degraded at Cr doping amounts of 0.68–1.3 atom% under visible light irradiation. At doping amounts above 1.7 atom%, the 4-CP degradation ratio increased for Cr–TiO2 sintered at 300–500 °C. X-ray photoelectron spectroscopy and X-ray absorption near edge structure measurements showed that only Cr(III) was present on the surfaces of Cr–TiO2 samples sintered at 200 or 400 °C and some of the Cr(III) in the bulk was oxidized to Cr(VI) by sintering at 400 °C. The 4-CP degradation was enhanced with increasing Cr(VI)/Cr(III) ratio in the bulk, suggesting the spatial separation of Cr(III) on the surface under visible light irradiation: electrons are excited from Cr(III) to the conduction band of TiO2 and then trapped at the doped Cr(VI) whereas the photogenerated Cr(IV) oxidizes 4-CP. Time-resolved diffuse reflectance spectroscopy was used to evaluate the lifetimes of the photogenerated electrons. The highest photocatalytic activity was obtained with ca. 0.8 atom% Cr–TiO2 sintered at 200 °C. This high activity is ascribed to the presence of oxygen vacancies, which act as electron-trapping sites.