Kerem Bozkurt

Abstract

This study focuses on the role of the combined gas diffusion layer and membrane on thermal diffusion coefficient and its effects on water transport in polymer electrolyte membrane fuel cell. Thermal diffusion coefficients were reported for water in typical membrane-electrode assemblies. Gas diffusion layers and, in some cases, microporous layers, surrounded the membrane in the center. The sign of the coefficient depended on the materials used. While the Teflon-coated and microporous layer-containing Sigracet 10BC type gas diffusion layer has positive coefficients, the Sigracet type 10BA and 10AA without such microporous layer have negative coefficients. The thermal diffusion coefficient has an activation energy, supporting the idea of water movement by activated jumps. We conclude that hydrophobic layers may significantly improve water and heat transport away from the cathode, and this is why reversible heat transfer should not be neglected in fuel cell studies.

Abstract

This study aims to measure thermo-osmotic water fluxes through membrane electrode assemblies consisting of membranes with different thicknesses and gas diffusion layers with different porosity and hydrophobicity properties. The experiments showed that the direction of thermo-osmotic water flux relies on the porosity of gas diffusion layers and the magnitude of the thermo-osmotic water flux change with the thicknesses of the membranes. This study is essential to clarify the disagreements on the thermo-osmotic water flux among the studies given in the literature.