分析了"自呼吸式"直接甲醇燃料电池膜电极性能衰减的因素及其影响程度。通过对膜电极进行2 000 h恒电流(25 m A/cm2)放电,对比了放电前后的极化曲线、交流阻抗谱及电化学活性面积。恒电流放电后,膜电极的最大功率密度从初始的29.1 m W/cm2下降到21.8 m W/cm2,开路电压基本不变;交流阻抗谱定量分析表明,阴极的电阻明显大于阳极,并且对膜电极性能衰减的影响程度是:阴极>>阳极>质子交换膜;循环伏安测试显示阴极催化剂电化学活性面积的衰减为21%,明显大于阳极催化剂的衰减2%。
Extremely small PtRu/C nanocatalysts were prepared via a carbonyl route. A thorough in situ reduction X-ray structural characterization of these catalysts was performed. After synthesis and storage under ambient condi- tions, the diffraction patterns of PtRu/C catalysts were seriously modified, indicating the surface oxide formation. In the reduced state, the particle size is around 2 nm. The observed relative fluctuations of lattice constants are 3%, which is far too large to be explained by a compositional fluctuation. Their origin is attributed to strong but isotropic strains and is related to the alloy formation. The annealing experiments show all the catalysts present an exceptional thermal stability when annealed in inert ambient, especially that of the Pt1Ru1/C catalyst. Besides, it is interesting to note that there is no thermal expansion evidence from the patterns.
