第一过渡系金属离子掺杂的TiO2纳米粒子光催化活性的研究

用溶胶-凝胶法制备纯的和分别掺杂第一过渡系金属离子(V5 、Cr3 、Mn2 、Fe3 、Co2 、Ni2 、Cu2 和Zn2 )的TiO2纳米粒子,以甲基橙的光催化氧化评价纳米粒子的活性,借助XRD考察掺杂对TiO2相变及粒径的影响,探讨金属离子的物化性质与其对TiO2性能影响的关系,研究掺杂改性的机制.结果表明:除Cr3 外的其它离子掺杂均能提高TiO2活性且最佳掺杂量相近,反应过程中V2O5析出使0.1%V-TiO2活性逐渐降低;掺杂均能轻微抑制锐钛矿向金红石的转变,对晶粒长大轻微抑制或无影响;离子适中的Ea/r及全充满或半充满的电子构型均有利于TiO2活性提高,两者谁占主导地位随掺杂离子不同而不同;离子化合价高于 4时高化合价对催化剂活性的正效应能完全克服不适的Ea/r与电子构型的负效应.第一过渡系金属离子掺杂对TiO2活性的影响由金属离子的Ea/r、电子构型及价态共同决定,与掺杂对TiO2结构相变和粒径的影响关系不大.

An Investigation on Photocatalytic Activities of the First Transition Metal Ions Doped TiO2 Nanoparticles

Pure and the first transition metal ions (V5+, Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+ and Zn2+) doped TiO2 nanoparticles were prepared by the sol-gel method. The photocatalytic oxidation of methyl orange was taken to evaluate the activity of nanoparticles. Effects of doping on the phase transformation and crystallite size of TiO2 were tested by XRD. The relationship between physicochemical properties of metal ions and their effects on the activity of TiO2 was discussed and the mechanisms of doping were studied. The results showed that most metal ions except Cr3+ doping could improve the activity of TiO2 and their optimum doping concentration was similar. The activity of 0.1%V-TiO2 gradually decreased with the increasing reaction time because of the segregation of V2O5. Doping could all slightly inhibit the transformation from anatase to rutile and slightly inhibit or had no effect on the grain growth. The proper Ea/r and the fully or half occupied electron configuration of metal ion were both benefit to improve the activity of doped TiO2, which occupies the leading position varying with metal ion type. Only when the valence of ion was higher than +4 can the positive effect brought by high valence completely overcome the negative effect brought by improper Ea/r and electron configuration on the activity of catalysts. Effects of the first transition metal ions doping on photocatalytic activity of TiO2 nanoparticles are found to be simultaneously dependent on Ea/r, electron configuration and valence of metal ions and independent on the effects of metal ions on the phase transformation and crystallite size of TiO2.