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Trondheim, Norway

Burheim O.,Institute Kjemi | Vie P.J.S.,Institute for Energy Technology of Norway | Moller-Holst S.,Sintef | Pharoah J.,Institute Kjemi | Kjelstrup S.,Institute Kjemi
Electrochimica Acta | Year: 2010

A calorimeter has been constructed and used to measure the total heat production of a single polymer electrolyte fuel cell that is operated on hydrogen and oxygen at 50 °C and 1 bar. The cell had a SolviCore Catalyst Coated Backing and Nafion membranes 112, 115 and 117. We report that the total heat production plus the power production corresponds to the enthalpy of formation of water for cell potentials above 0.55 V. For cell potentials less than 0.55 V, we measured a linear decrease in the reaction enthalpy with decreasing cell potential. This effect was obtained independently of membrane thickness and current density. We propose therefore that the main power loss at low cell potentials and the inflection point in the polarisation curve is due to hydrogen peroxide formation at the cathode. The total heat production was decomposed into reversible and irreversible effects (non-ohmic and ohmic). The non-ohmic part was evaluated using Tafel plots. We show that it is possible to determine the overpotential of an electrode also from its thermal signature. Crown Copyright © 2009.

Burheim O.,Institute Kjemi | Vie P.J.S.,Institute for Energy Technology of Norway | Pharoah J.G.,Institute Kjemi | Pharoah J.G.,Queens RMC Fuel Cell Research Center | Kjelstrup S.,Institute Kjemi
Journal of Power Sources | Year: 2010

In this paper thermal properties for materials typically used in the proton exchange membrane fuel cell (PEMFC) are reported. Thermal conductivities of Nafion membranes were measured ex situ at 20 °C to be 0.177 ± 0.008 and 0.254 ± 0.016 W K-1 m-1 for dry and maximally wetted membranes respectively. This paper also presents a methodology to determine the thermal conductivity of compressible materials as a function of applied load. This technique was used to measure the thermal conductivity of an uncoated SolviCore porous transport layer (PTL) at various compaction pressures. For the dry PTL at 4.6, 9.3 and 13.9 bar compaction pressures, the thermal conductivity was found to be 0.27, 0.36 and 0.40 W K-1 m-1 respectively and the thermal contact resistivity to the apparatus was determined to be 2.1, 1.8 and 1.1 × 10-4 m2 K W-1, respectively. It was shown that the thermal contact resistance between two PTLs is negligible compared to the apparatus' thermal contact resistivity. For a humidified PTL, the thermal conductivity increases by up to 70% due to a residual liquid saturation of 25%. © 2009 Elsevier B.V. All rights reserved.

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