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The significant use of platinum for catalyzing the cathodic oxygen reduction reactions (ORRs) has hampered the widespread use of polymer electrolyte membrane fuel cells (PEMFCs). The construction of well-defined electrode architecture in nanoscale with enhanced utilization and catalytic performance of Pt might be a promising approach to address such barrier. Inspired by the highly efficient catalytic processes in enzymes with active centers embedded in charge transport pathways, here we demonstrate for the first time a design that allocates platinum nanoparticles (Pt NPs) at the boundaries with dual-functions of conducting both electrons by aid of polypyrrole and protons via Nafion® ionomer within hierarchical nanoarrays. By mimicking enzymes functionally, an impressive ORR activity and stability is achieved. Using this brand new electrode architecture as the cathode and the anode of a PEMFC, a high mass specific power density of 5.23 W mg−1Pt is achieved, with remarkable durability. These improvements are ascribed to not only the electron decoration and the anchoring effects from the Nafion® ionomer decorated PPy substrate to the supported Pt NPs, but also the fast charge and mass transport facilitated by the electron and proton pathways within the electrode architecture. [ABSTRACT FROM AUTHOR]

Abstract: Carbon-supported Pt/PdCo and Pt/Au/PdCo catalysts with a low Pt loading were prepared by a combined underpotential deposition and galvanic replacement route. The X-ray diffraction results show that after annealing in H2/Ar atmosphere, the alloy degree of PdCo is enhanced. The average metal particle size of PdCo/C, PdCo/C-H, Pt/PdCo/C and Pt/Au/PdCo/C, characterized by transmission electron microscopy, is about 2.6, 4.1, 5.3 and 5.5nm, respectively. The electrochemical characterizations show that the Pt/PdCo/C electrocatalyst exhibits a high activity toward the oxygen reduction reaction (ORR) but is unstable in electrochemical environment. After the accelerated aging tests (AAT), the electrochemical surface area (ECSA) for the Pt/PdCo/C catalyst decreases by 48% and the half-wave potential of the ORR polarization curve (E 1/2) shifts 35mV negatively. After decorated by Au, both the catalytic activity and stability of the Pt/PdCo/C catalyst are improved significantly. Compared to Pt/PdCo/C, the E 1/2 for Pt/Au/PdCo/C shifts 22mV toward higher potentials. After the AAT, the ECSA decreases only 26%, and the E 1/2 shifts 13mV negatively for Pt/Au/PdCo/C. The enhanced catalytic activity and stability should be due to the high resistance to be oxidized for Pt and the suppressed OH adsorption on the Au-decorated Pt surface. [Copyright &y& Elsevier]