Electrochemical surface oxidation of platinum supported on carbon black (Vulcan XC-72, Pt/C) and carbon nanostructures (Pt/CNS) was studied to understand and compare the durability as catalyst support in polymer electrolyte membrane fuel cells (PEMFCs). The subsequent electrochemical characterization at different treatment time intervals suggests that CNS is more electrochemically stable than carbon black due to its higher degree of graphitization. Furthermore, the reported membrane electrode assembly durability measurements suggest that highly ordered CNS would be a better catalyst support than turbostratic Vulcan XC-72.