DMFC阳极催化剂的制备与性能影响因素研究

Preparation and influence of performance of anodic catalysts for direct methanol fuel cell

采用化学还原法制备了Pt-Ru/C催化剂,比较了在惰性气氛中还原和在空气中还原、升温后加入还原剂和加入还原剂后升温以及热处理温度对催化剂性能的影响;利用粉末微电极的动电位扫描和恒电位极化研究了上述催化剂对甲醇阳极催化氧化活性的影响;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:在惰性气氛保护下制备的催化剂性能优于在空气中还原制备的催化剂,Pt-Ru颗粒在碳载体上分布均匀,粒径较小,为4.5 nm.还原剂加入先后顺序不同影响催化剂的催化性能,在溶液升温后加入还原剂所制备的催化剂性能好于0℃加入还原剂再逐渐升温到还原温度所制备的催化剂.催化剂的热处理能够提高Pt-Ru金属的合金化程度,改变催化剂的结构,使Pt-Ru相互间分散的更加均匀,改善催化剂的稳定性,提高催化剂的使用寿命.

This research aims to increase the utilization of platinum-ruthenium alloy （Pt - Ru） catalysts and thus to lower the catalyst loading in anodes for methanol electrooxidation. The DMFCs anodic catalysts, Pt - Ru/C, were prepared by chemical reduction with a reducing agent added in hot solution under inert gases or air, and in cold solution under inert gases. The catalysts were treated at different temperatures. Their performance were tested by cyclic vohammetry and potentiostatic polarization with a powder microelectrode from them in 0.5 mol/L CH3OH and 0.5 mol/L H2SO4 solution, and their structures and micro-surface images were determined and observed by X - ray diffraction and transmission electron microscopy, respectively. The catalyst prepared in inert gases showed a better catalytic performance for methanol electrooxidation than that in air. It resulted in a more homogeneous distribution of the Pt - Ru alloy in carbon. Its size is small, about 4.5 nm. The catalytic performance is affected by different orders at reducing agent added. The performance of catalyst prepared by adding the reductant constant temperature of the solution is better than that prepared by adding it in the solution at 0 ℃ and then heated it up to the reducing temperature. The catalyst structure was modified, and there was an increase in the conversion of ruthenium into the alloyed state and an increase of particle size with the increase of heat treatment temperature. Its stability was improved after heat treatment.