Optimization of gas diffusion media for elevated temperature polymer electrolyte fuel cells

Elevated temperature operation (above 80 °C) of polymer electrolyte fuel cell (PEFC) is characterized by more difficult membrane hydration and low availability of oxygen to the cathode catalyst layer. Better membrane hydration and less resistance to oxygen transport are required for improved performance of PEFC, operated at elevated temperatures. Hence, diffusion media, being a gateway for reactant and product water transport between the gas channel and catalyst layer, require optimization to ensure an improved PEFC performance at elevated temperatures. In the present study, a functional dependence of cell voltage on diffusion media properties is characterized and a two-dimensional single-phase, non-isothermal model is used to study the effect of diffusion media properties on the performance of fuel cell operated at 95 °C. It was found that there exists an optimum value of effective diffusive length of diffusion media that provides peak performance. In addition, a functionally graded diffusion media design is proposed that provides a better performance than conventional diffusion media at elevated temperature operation.