三组Pt-Ru/C催化剂前驱体对其性能的影响

The Influence of Three Groups of Pt-Ru/C Catalyst′s Precursors on Its Performance for Direct Methanol Fuel Cell

分别以三组不同的Pt和Ru化合物为前驱体,采用热还原法制备了Pt-Ru/C催化剂,比较不同前驱体对催化剂性能的影响;通过XRD和TEM技术对催化剂的晶体结构及微观形貌进行了分析.结果表明以H2PtCl6+RuCl3和自制(NH4)2PtCl6+Ru(OH)3为前驱体的催化剂Pt和Ru没有完全形成合金状态,在Pt(111)和Pt(200)之间有Ru(101)存在;以Pt(NH3)2(NO2)2和自制含钌化合物为前驱体制备的催化剂未检测出Ru金属或其氧化物的衍射峰,Pt-Ru颗粒在载体上分散均匀,粒径最小,为3.7nm.利用玻碳电极测试了循环伏安、记时电流和阶跃电位曲线,考核了上述催化剂对甲醇阳极催化氧化活性的影响;结果表明:以Pt(NH3)2(NO2)2和自制含钌化合物为前驱体制备的催化剂对甲醇的电催化氧化活性最高,循环伏安曲线峰电流密度达11.5mA·cm-2.

This research is aimed to increase the activity of platinum-ruthenium alloy （Pt-Ru/C） catalysts and thus to lower the catalyst loading in anodes for methanol electrooxidation. The direct methanol fuel cell （DMFC） anode catalysts, Pt-Ru/C, were prepared from three groups of precursors by thermal reduction. The phase structure, particle size, size distribution and the morphology of reduced catalysts were determined by means of highresolution transmission electron microscopy （TEM） and X-ray diffraction （XRD）. It is found that XRD patterns of all the catalysts show Pt reflexion of a face centered cubic （fcc） crystal structure. But there are diffraction peaks indicating the presence of either pure Ru or Ru-rich hexagonal close packed （hcp） phase, which is not alloyed with Pt in Pt-Ru/C catalysts prepared from （NH4）2PtC16＋Ru（OH）3, or H2PtC16＋RuC13 as precursors. The catalyst prepared from Pt （NH3）2 （NO2）2 and Ru compound of self-prepared as precursors had a more homogeneous distribution of Pt-Ru alloy in carbon and a small particle size of about 3.7 nm. Their performance was tested using a glassy carbon working electrode by cyclic voltammetry（CV）, chronoamperometric and amperometric i-t curves in a solution of 0.5 mol·L^-1 CH3OH and 0.5 mol·L^-1 H2SO4 at 25℃. The electrocatalytic activity of Pt-Ru/C catalysts prepared from Pt（NH3）2（NO2）2 and Ru compound of self-prepared as precursors has the highest catalyficactivity for methanol electrooxidation. The peak current density in CV is 11.5 mA·cm^-2.