Current fuel cell research is focused on reducing manufacturing costs by reducing platinum catalyst loading without sacrificing performance. Although improvements have been demonstrated by using platinum supported on porous carbon nanoparticles, significant losses in "active" platinum surface area within the catalyst layer (CL) still occur. Optimizing the reactant gas/Nafion (R) /platinum triple phase boundary (TPB) in the CL (i.e., CL morphology) will result in increased "active" catalyst area and overall fuel cell performance. In this study, the effect of temperature on the formation of Nafion (R) nanofibers in the CL during fuel cell operation and its subsequent improvement on fuel cell performance was clearly characterized. Post mortem scanning electron micrographs clearly show that Nafion (R) nanofibers improve the TPB, where Nafion (R) nanofibers act as a more efficient proton transport route from the catalyst particles to the polymer electrolyte membrane reducing ohmic and mass transport resistance. (c) 2008 Elsevier B.V. All rights reserved.