铈掺杂TiO_2光催化降解甲基橙的研究

Study on Photocatalytic Degradation of Methyl Orange by Cerium-Doped TiO_2

采用溶胶-凝胶法制备纯的及掺杂不同量Ce的TiO2纳米粒子,利用UV-Vis漫反射光谱及XRD等对所制备样品进行表征和解释,以高压汞灯为光源,甲基橙水溶液的脱色为模型反应,研究了CeO2/TiO2的光催化降解反应活性。实验发现:掺杂Ce的TiO2纳米粒子反射光谱特性向可见光方向红移到了500 nm;掺杂Ce的TiO2纳米粒子比纯的TiO2纳米粒子对光的吸收率高、吸收能力强;掺杂的Ce4+仅有少量进入TiO2晶格中,而大部分的Ce4+没有进入TiO2晶格中,而是以小团簇的CeO2形态均匀地分散在TiO2纳米粒子中或者是覆盖在其表面上,说明掺杂Ce能提高TiO2光催化反应活性,且掺杂Ce量有最佳值。实验结果表明:在TiO2中掺杂Ce的摩尔百分含量为2%,甲基橙起始浓度为20 mg.L-1,CeO2/TiO2用量为0.400 g,双氧水用量为5.88 mmo.lL-1,pH值为6.4时,光照8 h,甲基橙的脱色率可达96.8%。

The nano-TiO2 particles pure and doped with varying content of Ce were prepared by a sol-gel process and characterized and explained by UV-V and XRD spectra. Being a model reaction, the photocatalytic degradation of methyl orange in aqueous solution in the present of CeO2/TiO2 nano-particles was investigated. The results show that Ce doping makes the reflective spectral characteristic of nano-TiO2 move to the visible region with a red shift to 500 nm, and Ce doping is favorable to enhancing the absorption of visible and UV light of nano-TiO2. It indicates that a few Ce^4＋ doped enter into the crystal lattices of TiO2, and a lot of Ce^4＋ doping does not enter into the crystal lattices of TiO2 and disperses uniformly into TiO2 or covers onto TiO2 as the form of CeO2 with small size, which suggests that Ce doping increases its photocatalyric activity, and has the optimum content of CeO2 in CeOE/TiO2 existed. The results show that the decolorizing efficiency of methyl orange can reach 96.8 % by using Ce doping 2% （molar fraction） in CeOE/TiO2 as heterogeneous photocatalyst, with initial concentration of methyl orange is 20 mg· L^- 1, amount of catalyst 2 0.400 g, amount of H202 2 5.88 mmol· L^-1, pH 2 6.4, illumination time 2 8 h.