GrafTech GRAFCELL® GDB Graphite Gas Diffusion Barrier

GRAFCELL® Gas Diffusion Barrier (GDB) material is a thin, perforated structure made from a continuous matrix of expanded natural graphite with excellent electrical conductivity, thermal conductivity, and corrosion resistance. GDB material can be engineered to provide the liquid and vapor permeability characteristics that are required to achieve an optimum balance of oxidant and product. It can be used as a standalone component or in conjunction with a gas diffusion layer to passively regulate the balance of incoming air and product water. It enables a method of operation that reduces or eliminates the need for an actively controlled external balance of plant systems. It also enables simplified flow field plate designs. GrafTech manufactures diffusion barrier material as a continuous roll good with open areas of 3%-15% . GDB material is used in applications such as self humidified PEM fuel cell stacks and air cooled PEM fuel cell stacks. In self humidified PEM fuel cell stacks, GDB passively regulates the diffusion of product water from the cathode, keeping the polymer electrolyte membrane hydrated and maximizing proton conductivity without the need for an external humidification system. In air cooled PEM fuel cell stacks, GDB’s directional permeability and water retention characteristics enable the stack to be operated with air flow rates that are sufficient to cool the stack, eliminating the need for liquid coolant pumps and external radiators.