甲醇浓度对Pt/C催化剂氧还原活性的影响

采用半池考察了Pt/C催化剂在含不同浓度甲醇的0.5mol/L硫酸中的氧还原活性(ORR).研究发现,当甲醇浓度为0.1mol/L时,Pt/C催化剂的ORR活性最高,在催化层上热压商品NafionNRE-212膜后也出现同样趋势.线性扫描伏安曲线显示,压膜前后的Pt/C催化剂的ORR活性在含0.1mol/L甲醇的0.5mol/L硫酸中几乎没有变化.电化学阻抗谱结果表明,在该溶液中,Nafion膜的电阻比在其它电解液中低,这可能是导致Pt/C催化剂ORR活性提高的主要原因.有必要关注Nafion膜的这一异常性质并通过特殊设计后用于电池堆,以提高燃料电池性能.

Effect of methanol concentration on oxygen reduction reaction activity of Pt/C catalysts

The oxygen reduction reaction (ORR) activity of Pt/C catalysts was investigated in electrolytes of 0.5 mol/L H₂SO₄ containing varying concentrations of methanol in a half-cell. It was found that the ORR activity was improved notably in an electrolyte of 0.5 mol/L H₂SO₄ containing 0.1 mol/L CH₃OH as compared with that in 0.5 mol/L H₂SO₄, 0.5 mol/L H₂SO₄ containing 0.5 mol/L CH₃OH, or 0.5 mol/L H₂SO₄ containing 1.0 mol/L CH₃OH electrolytes. The same tendency for improved ORR activity was also apparent after commercial Nafion^® NRE-212 membrane was hot-pressed onto the catalyst layers. The linear sweep voltammetry results indicate that the ORR activities of the Pt/C catalyst were almost identical in the 0.5 mol/L H₂SO₄+0.1 mol/L CH₃OH solution before and after coated with the Nafion^® membrane. Electrochemical impedance spectroscopy results demonstrated that the resistance of the Nafion^® membrane is smaller in the electrolyte of 0.5 mol/L H₂SO₄+0.1 mol/L CH₃OH than in other electrolytes with oxygen gas feed. This exceptional property of the Nafion^® membrane is worth investigating and can be applied in fuel cell stacks to improve the system performance.