Flaky and nanospherical birnessite and birnessite-supported Pt catalysts were successfully prepared and characterized by means of Xray diffraction (XRD),transmission electron microscopy (TEM),energy dispersive spectroscopy (EDS) and N2 adsorption-desorption.Effects of the birnessite morphology and Pt reduction method on the catalytic activity for the complete oxidation of formaldehyde (HCHO) were investigated.It was found that flaky birnessite exhibited higher catalytic activity than nanospherical birnessite.The promoting effect of Pt on the birnessite catalyst indicated that the reduction method of the Pt precursor greatly influenced the catalytic performance.Flaky birnessite-supported Pt nanoparticles reduced by KBH 4 showed the highest catalytic activity and could completely oxidize HCHO into CO2 and H2O at 50℃,whereas the sample reduced using H2-plasma showed lower activity for HCHO oxidation.The differences in catalytic activity of these materials were jointly attributed to the effects of pore structure,surface active sites exposed to HCHO and the dispersion of Pt nanoparticles.
Linlin LiuHua TianJunhui HeDonghui WangQiaowen Yang
采用一种简单的原位塌陷自组装法利用高锰酸钾(KMnO4)和油酸(OA)在O/W乳液界面上发生的"Baeyer test for unsaturation"反应,用乙醚作为共溶剂来制备氧化锰纳米结构.与之前相比,加入乙醚(EE)最大的优点是减少了反应过程中油酸的用量,大大简化了产品的洗涤过程,降低了制备成本.得到的产品分别用SEM,TEM和XRD进行了表征.产品的形貌和尺寸可以通过调控OA/乙醚体积比,KMnO4/OA物质的量比,油相/水相体积比和反应温度来实现.当OA/乙醚的体积比在10∶0～3∶7之间,KMnO4/OA物质的量比小于1∶1,或油相/水相体积比小于2∶45时,得到的产品形貌为蜂窝状;当OA/乙醚体积比低于3∶7,KMnO4/OA物质的量比大于0.67∶1,或油相/水相体积比大于2∶75时,得到的产品形貌为片状结构;当反应温度从25℃升高到33℃,产品的形貌、结构和尺寸变化不大,继续升高到45℃时,颗粒中的纳米片数量有所减少.依据所得的结果推断反应是通过一个纳米片不断塌陷的过程形成的.
