Pt, Au and Pd Based Binary and Ternary Catalysts for the Oxygen Reduction Reaction
Other noble metals were also considered for the activation of the ORR in acidic medium, such as palladium and gold. Amongst pure metals, palladium leads to the highest activity towards the ORR, just after platinum. A review paper of Antolini  cited numerous publications explaining that palladium-based alloys or core-shell structures could lead to activities towards the ORR higher than those observed on pure palladium, and almost comparable to those recorded on pure platinum. Pd-Co and Pd-Fe are the most cited metallic alloys because they are the most active, in agreement with DFT (Density Functional Theory) calculations. Recently, PtPd alloys with very low Pt atomic ratio led to remarkable fuel cell electric performances . Bimetallic PtxAu1-x catalysts have also led to excellent stability and activity under PEMFC working conditions, making this kind of materials a serious alternative candidate to platinum as cathode electrocatalysts in a PEMFC.
In comparison, few studies have been carried out on the behavior of trimetallic catalysts towards the ORR. PtFeNi nanoparticles showed excellent electrocatalytic performances under PEMFC working conditions . The research group of Manthiram studied Palladium-based trimetallic catalysts. They obtained activities towards the ORR comparable or even slightly higher to that of a Pt/C catalyst using Pd–Co–Mo/C and Pd–Co–Au/C materials. Although a few studies on trimetallic catalyst activity and stability is available in the literature, several trends could be drawn : (i) alloying platinum with a less noble metal seems to be beneficial for the ORR in terms of activity and tolerance, (ii) the interactions between two different noble metals such as Pt-Pd, Pt-Au and Au-Pd seems to enhance the durability and the catalytic activity towards the ORR with respect to pure metals and (iii) platinum seems unavoidable in order to achieve the best possible activity from the catalyst in an acidic environment. So in the present work, the synthesis and characterization of carbon supported Pt, Pd and Au based binary and ternary catalysts (PtxPdyAuz/C) are described as well as their systematic study (activity and selectivity) towards the ORR. The aim of this work is to allow defining a relevant catalyst formulation (composition and atomic ratio) for enhanced ORR performance.
Acknowledgement: The financial support of the European Commission under the FP7 Fuel Cells and Hydrogen Joint Technology Initiative grant agreement FP7-2012-JTI-FCH-325327 for the SMARTCat project is gratefully acknowledged.
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