A major challenge to full commercialization of the polymer electrolyte fuel cell (PEFC) is the cost of materials and performance. A focus for research and development is to reduce material costs while maintaining or improving performance under practical operating conditions. The challenge to reach optimal performance in commercial fuel cells requires optimization of electrochemical activity over the entire active area. This is necessary because in a practical fuel cell as reactants pass along the flow field channels between inlet and outlet the composition and other parameters will change as the reactant is consumed and products are formed.