PEMFC电化学氢泵活化方法及其强化机制

Electrochemical hydrogen pump activation method and mechanism of PEMFC

质子交换膜燃料电池(proton exchange membrane fuel cell,PEMFC)通常需活化才能发挥其最佳性能。与传统的活化方法相比,电化学氢泵可以节约时间和氢气成本。电化学氢泵是一种使氢气在阳极氧化成质子,然后质子在外加电场作用下迁移到阴极并且被还原成氢气的方法。借助极化曲线测试、交流阻抗测试和循环伏安测试等方法研究电化学氢泵活化后PEMFC的发电性能、内部阻抗和催化剂电化学活性比表面积(electrochemical specific area,ECSA)的变化,进而分析其活化机理。此外,研究不同电流密度、进气湿度和活化温度对氢泵活化效果的影响。结果表明:氢泵活化后,燃料电池发电性能显著提升,Tafel斜率降低,电荷传输阻抗和质量传输阻抗降低,欧姆阻抗基本不变,ECSA增加,因此氢泵活化机制与催化剂活性物种数量、催化层微观结构有关。在电流密度200 mA·cm^(-2)下氢泵活化的效果强于100 mA·cm^(-2)。在进气湿度为150%RH下氢泵活化的效果强于100%RH和200%RH。另外,活化温度对氢泵活化效果的影响不大,在常温下氢泵活化30 min即可使燃料电池完全活化。

Proton exchange membrane fuel cell(PEMFC)usually need an activation process to obtain its best electrochemical performance.Compared with the traditional activation methods,electrochemical hydrogen pump has the advantages of saving time and hydrogen cost.The electrochemical hydrogen pump is a method in which hydrogen is oxidized into protons at the anode,and the protons migrate to the cathode with an applied electric field,and then are reduced to hydrogen again.The performance,internal impedance and electrochemical specific area(ECSA)changes of PEMFC after electrochemical hydrogen pump activation were studied with the help of polarization curves,electrochemical impedance spectroscopy(EIS)and cyclic voltammetry(CV)tests.Then the mechanism of the hydrogen pump activation was analyzed.Moreover,the influence of different current densities,inlet humidities and activation temperatures were investigated.The results show that after the hydrogen pump activation,the fuel cell performance is improved obviously,the slope of Tafel curve is decreased,the charge transfer resistance and mass transfer resistance get lower values,while the ohmic resistance is basically unchanged,and the ECSA is increased.Therefore,the mechanism of the hydrogen pump activation is related to the quantity of active species and microstructure of catalyst layer.The performance of hydrogen pump activation under 200 mA·cm^(-2)is better than that of under 100 mA·cm^(-2).The performance of hydrogen pump activation under the inlet humidity of 150%RH is better than that of 100%RH and 200%RH.In addition,the activation temperature has little impact on the PEMFC performance after hydrogen pump activation,and the fuel cell can be fully activated by hydrogen pump activation for 30 min at room temperature.