Membrane electrode assemblies for PEM fuel cells: A review of functional graded design and optimization

The use of platinum as a catalyst and the nonuniform distribution of current density inside a membrane electrode assembly result in high cost and low durability, which strongly hinders the wide adoption of proton exchange membrane fuel cells. For proton exchange membrane fuel cells operated at various loads, the required activities and mass transport rates are different because the reactant and product are nonuniformly distributed inside the membrane electrode assembly. Thus, a rational design for a membrane electrode assembly with a spatial distribution of functional components is helpful for reducing the usage of precious components, improving cell performance, and achieving uniform distributions of current density and heat. Herein, the graded design of the functional components in the gas diffusion layer, microporous layer, catalyst layer, and membrane along both the through-plane and in-plane directions within the membrane electrode assembly are reviewed for the purpose of reducing the cost and improving the performance and durability of proton exchange membrane fuel cells.