Investigation of Pt/CNT-based electrodes in proton exchange membrane fuel cells using ac impedance spectroscopy

Abstract

An integrated platinum/carbon nanotube (CNT)-based electrode for proton exchange membrane fuel cells (PEMFCs) was efficiently prepared by combining in situ CNT growth and direct Pt sputter-deposition processes. This Pt/CNT-based electrode demonstrated a pronounced improvement in polarization curve characterization compared with two carbon black-based electrodes with commercial Pt/VXC72R catalysts. In situ electrochemical impedance spectroscopy (EIS) was used to investigate the impedance behavior of the Pt/CNT-based electrode, and results showed that the performance improvement of the Pt/CNT-based electrode can be attributed to its enhanced charge-transfer and mass transport properties. The EIS results were further verified by the transmission electron microscopy micrographs on the microstructure of the integrated Pt/CNT catalyst. In addition, the overall effectiveness of the Pt/CNT-based electrode has been validated at both the anode and the cathode by polarization curve and EIS characterizations. It has been revealed that the EIS technique can provide more explicit information than polarization curves on the performance dependence on charge-transfer and mass transport processes at different overpotential regions. It also provides insightful information in optimizing the structure and synthesis for PEMFC electrodes. © 2010 The Electrochemical Society.