Gradient Carbon Composite Materials for Hydroagen Processing Technologies

Consideration is given to the state of the art in the production of materials of carbon felt-based gas diffusion layers. It is shown that the nature of a hydrophobic polymer (polyvinylidene-fluoride, PVDF, and polytetrafluorethylene, PTFE) has no crucial effect on the water contact angle (limiting wetting angle), however, it is of fundamental significance in terms of regulation of the macroporous structure and surface electrical resistance of the obtained materials. Thus, polytetrafluorethylene concentrates predominantly in the near-surface layers while polyvinylidenefluoride spreads uniformly through the thickness of the carbon support. Furthermore, the concentration of an impregnating solution of PTFE (fluorine plastic) suspension makes it possible to regulate efficiently the surface properties of felts, which can be directly used in the development of gas diffusion layers of fuel cells. On the whole, the use of viscose fiber-based carbon felts allows the production of gas diffusion materials with a level of surface electrical resistance below 1 Ω/m².