Preparation and evaluation of a highly stable palladium yttrium platinum core–shell–shell structure catalyst for oxygen reduction reactions

• Core–shell–shell structure Pd–Y–Pt/C catalyst was synthesized using controlled surface reaction method for the first time.
• Nano-scale yttrium was reduced to zero-valent and formed a shell located as the middle layer of the catalyst.
• Higher ORR activity compared to Pt/C (20%) with only 7% Pt.
• More stable than Pt/C and Pd–Pt/C catalysts.

A core–shell–shell structure Pd–Y–Pt/C catalyst was prepared using a controlled surface reaction method. The structure was confirmed by X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray (EDX) techniques. Nano-scale yttrium was formed as a shell located as the middle layer of the catalyst. Electrochemical evaluation of the Pd–Y–Pt/C with less than 7% of Pt showed an improved performance toward oxygen reduction reaction (ORR) compared to Pt/C (20 wt.% Pt). Accelerated degradation tests (ADT) indicated that the addition of Y improved catalyst stability compared to Pt/C and Pd–Pt/C core–shell catalysts under various experimental conditions. This was due to the Y middle layer created approximate half-filled metal–metal d bond between Pt (or Pd) and Y. This catalyst utilized the core–shell–shell structure to minimize the Pt usage, and Y middle shell to improve stability.

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