用溶胶-凝胶法制备了La或Ce改性的0.3%Ni/TiO2(即La-Ni/TiO_2或Ce-Ni/TiO_2),考察了La-Ni/TiO_2或Ce-Ni/TiO_2在催化降解甲基橙水溶液过程中的重复利用性能,并用XRD、N_2吸附-脱附以及XPS等手段对催化剂进行了表征分析.研究表明,适宜La和Ce掺杂量(La/Ti、Ce/Ti摩尔比)分别为0.15%和0.1%,适宜焙烧温度为400℃.在酸性条件下(pH=3),La-Ni/TiO_2和Ce-Ni/TiO_2与Ni/TiO2光降解甲基橙的能力相当,但La或Ce掺杂使Ni/TiO_2催化剂的重复使用能力提高.催化剂上存在低结合能的低价钛离子(如Ti~(3+)),低价钛离子的含量和结合能大小是衡量催化剂光催化降解活性的重要因素.可能是La或Ce使催化剂在使用过程中低价钛离子得到较好保留,从而使催化剂活性得到较好维持,催化剂重复使用性能提高.
La-Ni/TiO_2 and Ce-Ni/TiO_2 were prepared by the sol-gel method and characterized by X-ray diffraction (XRD),X-ray photoelectron spectroscopy (XPS) and N_2 adsorption-desorption. The photocatalytic activities of the catalysts were investigated by degradation of methyl orange in aqueous solution. Both La-Ni/TiO_2 and Ce-Ni/TiO_2 photocatalytic activities were almost equal to that of Ni/TiO_2 in acid aqueous solution(pH=3). The photocataltic activities on used La-Ni/TiO_2 and Ce-Ni/TiO_2 were much more than that on used Ni/TiO_2. It was found that there were low valence titanium ions with lower binding energy (such as Ti~(3+)) on the surface of Ni/TiO_2,La-Ni/TiO_2 and Ce-Ni/TiO_2. The percentage and the binding energy value of low valence titanium ions on the catalysts were important in photocatalytic degradation of pollutants. It is speculated that lanthanum and cerium make the loss of nickel in the La-Ni/TiO_2 and Ce-Ni/TiO_2 lower and low valence titanium ions be more in used La-Ni/TiO_2 or used Ce-Ni/TiO2 than that in used Ni/TiO_2. This was the reason why the photodegradation activity of La-Ni/TiO_2 and Ce-Ni/TiO_2 were higher than that of Ni/TiO_2 in recycling processes.
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