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The sluggishness of the oxygen reduction reaction (ORR) on the Pt surface at the cathode and the accompanying large amounts of Pt necessary to fabricate a single cell have been significant drawbacks in the commercialization of proton exchange membrane fuel cells (PEMFCs). Numerous strategies have been reported for either controlling the electronic structure of the catalyst favorable to oxygen reduction or enlarging the surface area of the catalyst by revealing a specific surface crystalline plane, controlling the nanostructure, making a transition metal alloy, or controlling the particle size and dispersion. However, in spite of the significant enhancement in the ORR activity, most of the novel nanostructured electrocatalysts can hardly be used in membrane electrode assembly due to difficulties in complex synthesis and in fabricating supported catalysts on carbon. Therefore, Pt-based alloy catalysts on carbon are a promising candidate to replace the pure platinum catalyst in the near future. However, there are barriers to the application such Pt alloy catalysts, such as dissolution of the second metal and the different reducing speed of ions during synthesis due to the different reduction potentials. Studies attempting to overcome the latter problem have focused on adding various types of stabilizer to balance the different reducing speeds. However, there are numerous candidate transition metals for making Ptbased alloy catalysts including Co, Fe, Ni, and Y. Finding an optimal stabilizer to make these alloys more effectively, i.e., the alloy content, particle size/size distribution, and dispersion on carbon, is a very important prerequisite in the development of an alloy catalyst for PEMFCs. We have recently reported that the PtCo/C alloy catalyst synthesized in the presence of CTAB (hexadecyltrimethylammonium bromide, C19H42BrN) as a stabilizer exhibited twice the mass activity toward ORR compared to commercial Pt/C, which is superior to other stabilizer-mediated synthesized PtCo/C catalysts. In this study, as a part of the attempts to find a suitable stabilizer for the synthesis of other Pt-transition metal alloy catalysts, we investigated the use of a series of stabilizers in the synthesis of PtFe/C. We consider that the study results will support the discovery of a universal and effective stabilizer for alloying many transition metals with Pt. Such a stabilizer will support the development of a Ptbased binary alloy, as well as ternary alloy catalysts with an activity significantly enhanced compared to that of the binary alloy catalyst. The transmission electron microscopy (TEM) analysis results of the PtFe/C catalysts synthesized with various surfactants are depicted in Figure 1(b) to (d), in comparison with commercial 40% Pt/C catalyst (a). The stabilizers were added to give a content equivalent to 5 times the total molar content of Pt and Fe ions. Since any residual stabilizer on the catalyst surface after synthesis deteriorates the activity of the catalysts by blocking the surface, all PtFe/C catalysts were heat treated to remove the stabilizers from the catalyst surface at either 250 C (CTAB and TOAB (tetraoctylammonium bromide, C32H68BrN)) or 350 C (OAM, oleylamine, C18H37N), where these temperatures were predetermined from temperature-programmed reduction. The particle size and size distribution of each catalyst have different aspects. In the case of the commercial Pt/C catalyst (Fig. 1(a)), the Pt nanoparticles of diameter 1 to 5 nm were well

Stabilizer-mediated Synthesis of High Activity PtFe/C Nanocatalysts for Fuel Cell Application