Electrochemical hydrogen pump activation method and mechanism of PEMFC

Abstract

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.

Keywords

• proton exchange membrane fuel cell
• electrochemical hydrogen pump activation
• electrochemical impedance spectroscopy
• cyclic voltammetry