Enhanced activity and stability of a Au decorated Pt/PdCo/C electrocatalyst toward oxygen reduction reaction

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 5.5 nm, 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 (E1/2) shifts 35 mV 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 E1/2 for Pt/Au/PdCo/C shifts 22 mV toward higher potentials. After the AAT, the ECSA decreases only 26%, and the E1/2 shifts 13 mV 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.

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► Pt/Au/PdCo/C was obtained by consecutive UPD-replacement on PdCo/C substrate.
► Pt mass activity toward the ORR for Pt/Au/PdCo/C was 4-fold of that for Pt/PdCo/C.
► The stability of Pt/Au/PdCo/C was enhanced significantly via Au decoration.
► The improvements were ascribed to the suppressed OH coverage on Au decorated Pt.