摘要:
为评价直接甲醇燃料电池（DMFC）阳极的稳定性,利用扫描电化学显微镜和常规电化学技术,研究了变压加载过程中DMFC阳极性能的变化。结果表明,在探针扫描过程中,经不同电压加载后的DMFC阳极表面的扫描电流呈相似的锯齿状分布。当阳极加载2 h,随加载电位升高,扫描峰电流的数量减少,对应峰电流的数值则先增大再减小,表明阳极的催化活性处于不均匀分布状态且随加载时间延长和加载电位升高而逐渐降低。在不同加载电位下,随加载时间延长,循环伏安曲线上的正向和反向电流峰先负移再正移,但抗CO性能持续降低。DMFC阳极在0.6 V下分别加载16 h和72 h后,催化剂粒径由3.4 nm分别增大到3.6 nm和4.4 nm。在0.8 V下加载72 h后,Pt/Ru重量比由2.0增加到3.9。变压加载使催化活性的不均匀分布加剧催化剂粒径长大,Ru流失加快,从而导致阳极催化性能衰减。
Abstract:
By scanning electrochemical microscopy ( SECM ) and traditional electrochemical method, the effect of loading potential variation on direct methanol fuel cell ( DMFC ) anode performance was studied. When the anode was loaded for 2 h at different potential, the number of peak current reduced with loading potential increasing while the corresponding peak current value increased first and then decreased, which manifested that the anodes catalytic distributed rather differently and reduced with loaded time and potential. The forward and the reverse sweep current peaks in cyclic voltammetry also first moved to negative and then shifted to positive with loaded time increasing while its resistance ability to CO continuously decreased. After loaded for 16 h and 72 h at 0.6 V, the average size of catalysts changed from 3.4 nm to 3.6 nm and 4.4 nm, respectively. While loaded for 72 h at 0.8 V, the weight ratio of Pt/Ru in catalyst changed from 2.0 to 3.9. Changing loaded potential exacerbated the uneven distribution of catalytic site, catalyst particle enlargement and Ru lose, which contributed to the catalytic activity deterioration.
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