(208b) Tailoring Pore Structure and Properties for Improved Water Management in PEM Fuel Cells Using Porous Bipolar Plates

Proton exchange membrane fuel cells (PEMFCs) have attracted much interest due to their potential applications in transportation and in stationary, portable, and emergency backup power. One of the critical issues associated with the performance and durability of PEMFCs is water management, which is of concern, especially for devices operating below 100 °C when liquid water is present. In such devices, it becomes necessary to maintain a balance between membrane dehydration and electrode flooding. Sufficient water activity is required for the hydration of the proton exchange membrane to obtain adequate proton conductivity. However, water accumulation in gas diffusion layers must be avoided so that the flow of reactant gases (H₂ and air/oxygen) is not inhibited.

In this study, a microporous bipolar plate was designed and characterized to improve water management in PEMFCs. The bipolar plates were synthesized using graphite particles of different shapes and sizes, a thermally curable phenolic resin, and different pore-forming additives (porogens). The porosity of the plates was tailored for the desired up-take of water (produced during fuel cell operation) through capillarity while offering sufficient resistance to permeability and leakage of reactant gases. Additionally, the pore surface was chemically modified using surface modification methods, including acid, hydrogen peroxide, and metal oxide treatment, to enhance hydraulic permeability. Operational characteristics such as water-uptake by wicking and suction (vacuum fill), gas breakthrough pressure, hydraulic permeability, electrical conductivity, and flexural strength of the plates, were measured and correlated with the graphite grade, porogen type, and plate porosity.¹ The results of these studies will be presented and discussed.

References:

1. Krishnan, S.; Harrington, M.; Pitchiya, A. P.; Putnam, Z.; Orlowski, D., Material Compositions And Methods For Porous Graphite-Polymer Composite Bipolar Plates. U.S. Patent Application 16/558,857: 2020.