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纳米技术与精密工程第11卷第2期
以500℃下煅烧制备的TiO2样品为催化剂,考察了pH值对COU反应液荧光强度的影响,结果如图9所示,其中,COU质量浓度为1.0×10-3mol/L,催化剂用量为1g/L,紫外光照射时间为1h.可以看出,在酸性条件下,随着溶液pH值的减小,反应液的荧光强度逐渐增强,表明产生的·OH逐渐增多.这是由于随着pH值的减小,TiO2的导带和价带电位呈下降趋势,价带电位降低使得空穴氧化H2O/OH-产生·OH的能力增强,从而导致·OH产量的增加.此外实验发现,在碱性环境中,COU的性质开始发生变化,因此难以通过COU与·
果表明随着煅烧温度的升高,TiO2颗粒逐渐从锐钛相转变为金红石相,带隙从3.21eV减小为3.04eV,颗粒逐渐增大、主要以类球形为主.光催化实验表明,随着煅烧温度的升高,样品的光催化活性呈现出先增大后减小的趋势,500℃下煅烧制备的样品光催化性能最好;随着催化剂用量的增加,光催化效率呈先增大后减小的趋势,最佳催化剂用量为4.0g/L;在pH值不太高时(≤7.2),光催化效率随pH值的升高呈下降趋势.·OH检测表明,其产率随样品煅烧温度、催化剂用量及pH值的变化规律与光催化效率的变化规律基本一致,表明·OH可能是光催化降解有机染料的主要活性物种.参考文献:
OH的反应来准确检测反应溶液中·OH的信息.
250200荧光强度150100500350
400
450500
波长/nm
pH=1.5pH=3.7pH=6.1
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