Celtec-V is a proton exchange membrane based on polybenzimidazole ͑PBI͒ comprising an interpenetrating network of polyvinylphosphonic acid designed for application in the direct methanol fuel cell. The properties and fuel cell performance of Celtec-V are investigated and compared against a Nafion 117 standard. It is shown that with the PBI-based membrane, fuel cell performance can be sustained to higher methanol feed concentration at around half the methanol crossover rate. Above 1.0 M methanol, Celtec-V outperforms Nafion 117. Furthermore, lower water permeation is observed, with Celtec-V having an electro-osmotic drag coefficient of around 1 compared to a value of 4-5 for Nafion 117. Room for improvement is identified in the ohmic resistance of the membrane and the cathode-membrane interface, where higher losses are observed at increasing current density.
The CO tolerance of commercial Pt and PtRu anode electrodes from different suppliers (E‐Tek and Tanaka) has been examined in polymer electrolyte fuel cells (PEFC) using AC‐impedance spectroscopy along steady‐state current‐voltage curves. A simple mathematical model has been derived in order to extract important kinetic parameters for CO poisoning on different anode electrodes. The Tanaka PtRu (40:60) electrode demonstrated the best CO tolerance under the selected operating conditions.Inductive behavior in the low frequency region of the impedance spectra for the E‐Tek Pt and PtRu electrode proved to be characteristic for CO poisoning. However, the impedance spectra of the Tanaka PtRu electrode did not show any inductive behavior and its CO surface coverage, extracted by fitting the experimental data to the model, was lower than the surface CO coverage of the E‐Tek electrodes.
In another paper in this volume, it is demonstrated that the electrochemical interface in MEAs, and thus the polarization performance of the resulting fuel cells, can be improved by optimising the hot‐pressing procedure in the MEA preparation. In particular, the extent of drying of the membrane during MEA preparation was shown to be critical. In the present investigation, the effect of the drying process, and thus water content, on the hydrophilicity, wetting, and surface energies of some fuel cell membranes is examined. Wetting and surface energies are well known to influence the bonding behaviour of materials. Conclusions about how membrane drying and changes in water content influence membrane bonding and the relative importance of these surface effects are drawn.
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