Transport Issues in Polymer Electrolyte Fuel Cells

This paper describes recent attempts to define and understand important transport issues that control performance and durability of polymer electrolyte fuel cells. The transport phenomena occurring in fuel cells are characterized by a large range of length and time scales. As examples, we will discuss oxygen/proton transport and water distribution in the microscopically complex catalyst layer at the pore level (microscale, ~µm), water management in the membrane-electrode assembly (MEA) (mesoscale, ~mm), lateral diffusive transport of species and electron transport in the gas diffusion layer over the land between two neighboring gas channels (mesoscale), and multi-dimensional flow, thermal transport, and multi-component species transport on the macroscale (~cm). In addition, a comprehensive physico-chemical modeling framework of combining electrochemistry with multi-scale transport is presented for an industrial-scale fuel cell. Areas for future research into transport issues in fuel cells are pointed out wherever appropriate. 1