Analysis of Gas Diffusion Layer and Flow-Field Design in a PEMFC Using Neutron Radiography

Abstract

A carbon-cloth gas diffusion layer ͑GDL͒ displays better performance than a carbon-paper GDL under humidified conditions. A straight flow field displays better performance than a serpentine flow field. To investigate these phenomena, neutron radiography was used to compare the amount of liquid water that accumulated in test fuel cells. It was found that a larger amount of water accumulated in a carbon-cloth GDL than in a carbon-paper GDL. From the viewpoint of cell performance, the carbon-cloth GDL was less influenced by the accumulated water than the carbon-paper GDL. It is assumed that the broader pore distribution of a carbon-cloth GDL creates oxygen-diffusion paths even if water accumulates in the GDL. With a serpentine flow field, water accumulated in the corner and the gas bypassed the flow field. These phenomena are the main causes of performance deterioration with a serpentine flow field.

Experimental measurement of effective diffusion coefficient of gas diffusion layer/microporous layer in PEM fuel cells

“…Consequently, better water transport in carbon-cloth GDL over carbon-paper GDL under humidified conditions can be expected [27]. Many features of GDL can be controlled during its manufacturing to obtain desired properties.…”

Modification of gas diffusion layers properties to improve water management

“…In this context, it may be stated that a more homogeneous current density distributions would likely extend the life time of the fuel cell, as mentioned in [23,24]. It should be noted that the water management is influenced by many effects, e.g., water removal due to high reactant flow rate [25] or GDL oxidation by substances as hydrogen peroxide and sulfuric acid degrades fuel cell operation [16,26].…”

New Concepts in the Chemistry and Engineering of Low‐Temperature Fuel Cells

“…However, quantitative experimental data regarding the dynamic behavior of water within the gas diffusion layer (GDL) structure is critical to developing accurate water distribution models [239]. The three major imaging techniques for monitoring water transport in a fuel cell are neutron radiography, X-ray microtomography (microCT), and magnetic resonance imaging (MRI) [233,234,[236][237][238]242]. Neutron radiography provides two-dimensional maps of liquid water in fuel cells and thus can neither determine the location of the liquid water, such as within the GDL or in the flow field, nor resolve water distribution throughout the three-dimensional GDL [236].…”