Fe3O4 catalyst supported on spherical γ-Al2O3 was prepared with and without ultrasonic treatment during the impregnation step,and the heterogeneous catalytic oxidation of dimethoate wastewater was conducted with Fent...Fe3O4 catalyst supported on spherical γ-Al2O3 was prepared with and without ultrasonic treatment during the impregnation step,and the heterogeneous catalytic oxidation of dimethoate wastewater was conducted with Fenton reagent.Then,the physical and chemical properties of the catalysts were analyzed by means of XRD,ICP-AES and SEM,especially the effect of Fe3O4 dispersity on γ-Al2O3.The results showed that the activity of the supported catalysts prepared with ultrasonic treatment for dimethoate was higher than those without ultrasonic treatment and the corresponding degradation rate doubled those of the catalyst obtained by impregnation.The probable cause was that for catalysts prepared with ultrasonic treatment,Fe3O4 was well dispersed on the catalyst surface with small particle size,or existed in non-crystalline amorphous state,and Fe content on the catalyst surface was higher than those without ultrasonic treatment.展开更多
文摘Fe3O4 catalyst supported on spherical γ-Al2O3 was prepared with and without ultrasonic treatment during the impregnation step,and the heterogeneous catalytic oxidation of dimethoate wastewater was conducted with Fenton reagent.Then,the physical and chemical properties of the catalysts were analyzed by means of XRD,ICP-AES and SEM,especially the effect of Fe3O4 dispersity on γ-Al2O3.The results showed that the activity of the supported catalysts prepared with ultrasonic treatment for dimethoate was higher than those without ultrasonic treatment and the corresponding degradation rate doubled those of the catalyst obtained by impregnation.The probable cause was that for catalysts prepared with ultrasonic treatment,Fe3O4 was well dispersed on the catalyst surface with small particle size,or existed in non-crystalline amorphous state,and Fe content on the catalyst surface was higher than those without ultrasonic treatment.
文摘研制高活性的Fe/N/C氧还原催化剂对于降低燃料电池成本、实现商业化应用有重要意义.为实现Fe/N/C催化剂的理性设计,需要深入研究其活性位结构.本文发展一种研究活性位结构的新策略,以预先合成好的聚间苯二胺基Fe/N/C催化剂(Pm PDA-Fe Nx/C)为起始物,对其在1000~1500 o C高温下再次进行热处理并使其失活,通过关联催化剂热处理前后的结构变化与氧还原催化性能来揭示活性位结构.实验结果表明,随着热处理温度升高,活性中心结构被破坏,铁原子析出团聚并形成纳米颗粒,氮元素挥发损失,导致催化剂失活.XPS分析显示,低结合能含氮物种的含量与催化剂的ORR活性呈良好的正相关性,表明活性中心很可能是由吡啶N和Fe-N物种构成的.
