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Abstract: Pt nanoparticles are encapsulated in the fourth-generation hydroxyl-terminated poly (amidoamine) (PAMAM) dendrimer (G4-OH) and anchored onto carbon to realize a novel cathode catalyst for polymer electrolyte fuel cells (PEFCs). Extensive physical and electrochemical characterizations confirm that Pt/G4-OH-C catalyst exhibits significant enhancement of catalytic activity towards oxygen reduction reaction (ORR). The mass activities (AmgPt −1) at 0.9V vs. RHE for Pt/G4-OH-CI and Pt/G4-OH-CII, both prepared by different routes, are enhanced by 3.6 and 2.6 times, respectively, in relation to Pt/C catalyst. Dendrimer template studied here provides size-controlled preparation of Pt-based catalyst and facilitates uniform dispersion and loading of the catalyst onto carbon support. It is noteworthy that a PEFC comprising Pt/G4-OH-C catalyst with a Pt loading of ∼0.1mgcm−2 delivers a power density of 712mWcm−2 at 0.6V with H2 and O2 feeds. By contrast, the PEFC using Pt/C with a Pt loading of ∼0.2mgcm−2 delivers a power density of only 370mWcm−2 while operating under similar conditions. [Copyright &y& Elsevier]