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.

摘要采用X射线衍射/扫描电镜/原子吸收/程序升温还原/X射线吸收近边吸收谱/X射线光电子能谱/氮吸附等手段对水热合成(HS)/等体积浸渍(PVI)与离子交换(IE)法制备的CuSAPO-34样品进行了表征, 并评价了老化前后催化剂上C3H6-SCR与NH3-SCR脱除模拟柴油车尾气中NOx的反应活性. 结果表明, IE法制得的催化剂活性最高, 尤其在C3H6-SCR低温阶段; PVI法制得的催化剂活性最差. 制备方法影响CuSAPO-34催化剂的比表面积/孔径分布和活性组分价态从而改变其催化活性. 各催化剂均存在Cu+和Cu2+, 但比例明显不同. HS样品以Cu2+为主, 另两种样品则含较多的Cu+. 老化不仅部分破坏了分子筛的形貌/降低了分子筛的比表面积, 尤其是表面Cu含量, 而且有部分Cu生成了CuSO4, 使得老化后催化剂的脱硝活性降低. PVI法制得的催化剂老化后活性下降幅度最小, 表明该分子筛抗老化能力较强.

Graphical AbstractThe ORR activity of 20 wt% Pt/C catalyst was enhanced notably due to a smaller resistance of Nafion membrane in the electrolyte of 0.5 mol/L H2SO4 containing 0.1 mol/L methanol with oxygen gas feed.Figure optionsDownload as PowerPoint slide