Investigating the role of graphite and reduced graphene oxide in the fabrication of microporous layers for proton exchange membrane fuel cells

Proton exchange membrane fuel cells (PEMFCs) require efficient water management. Microporous layers (MPLs) are crucial to solve this problem due to their positive effects on the two-phase mass transfer process. The performance of MPLs is mainly determined by the properties of the materials used for their construction as well as other basic transport properties, including morphology, porous structure, wettability, and electrical resistivity. In this study, graphite and reduced graphene oxide (rGO) were used as the main components to fabricate MPLs for use in PEMFCs because they are highly conductive and thermally efficient. Single-layer MPLs are prepared by compressing MPL powders with different proportions of ingredients. In contrast, two-layer gas diffusion layers were fabricated by applying MPL pastes to a benchmark Toray carbon paper using a screen-printing process. FTIR and XRD analysis of main components and some samples are performed to investigated functional groups and the nature of MPLs' surface, respectively. An analysis of the effects of graphite, rGO, and hydrophobic agents' constituents on the physical properties (electrical resistivity, contact angle, roughness, porosity, and permeability) of the fabricated MPL or MPL-coated carbon papers by screen-printing method has been performed. Also, the effect of different coating methods (screen-printing and spraying) on different properties of graphite-based and rGO-based MPLs has been investigated. The results show that composites based on rGO have higher electrical resistivity than that of graphite-based MPLs, but lower roughness. However, MPLs based on rGO exhibit better contact angle, higher porosity, and improved gas permeability. Moreover, as expected, the contact angle and electrical resistivity increase, while the porosity and permeability decrease when the hydrophobic agents (polytetrafluoroethylene, and polyvinylidene difluoride) which are also used as binders, are increased. On the other hand, screen printed graphite-based MPL has lower electrical resistivity, while screen printed rGO-based MPL has higher porosity percentage, roughness, and permeability than the sprayed one. [GRAPHICS]