here Pt, was deposited on the CNNs. The influence of surfactant type, Na-AOT or Triton X-100, carbon synthesis catalyst type, Fe, Co or Pt, and loading on the electrolyte accessible surface area (ESA) and carbon corrosion resistance was evaluated in a three-electrode half-cell. CNNs grown from Fe and synthetized in Na-AOT microemulsions resulted as the best combination in terms of ESA and carbon corrosion resistance and were used for subsequent investigations. The CNNs grown on CP (CNNs/CP) were electrochemically oxidized prior to Pt electro-deposition by means of potential cycling. The effect of oxidation of the CNNs on the size and spatial distribution of the electrodeposited Pt catalyst was evaluated. Increasing the number of functionalizing oxidation cycles from 0 to 100 decreased the average catalyst crystallite size from 19 to 9 nm. The CNNs/CP samples showing the highest electrochemically active surface area (ECSA) were compared to a commercial catalyst with respect to ECSA, catalyst utilization, and durability to potential cycling. The ECSA for the CNNs/CP samples turned out to be lower than that of the commercial catalyst due to the larger catalyst size. On the other hand, the CNN/CP samples proved to be more durable and higher Pt utilization was achieved.