Abstract
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 (20wt.% 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.
Highlights
Catalyst is the most important factor which governs the performance of polymer electrolyte membrane fuel cells (PEMFCs)
A controlled surface reaction (CSR) method for core–shell catalysts preparation was previously reported by Crabb et al [15,16], this method utilizes the reaction between an organometallic compound and the core metal surface in a hydrogen environment, and the surface composition was well controlled
X-ray photoelectron spectroscopy (XPS) indicated slightly higher values of Pt and Pd and lower value of Y, this could be attributed to electronegativity differences, Table 1 Preparation and XPS elementary analysis of Pd–Y–Pt/C and Pd–Pt/C catalysts
Summary
Catalyst is the most important factor which governs the performance of polymer electrolyte membrane fuel cells (PEMFCs). Researchers found that Pd based alloys can be a good candidate to replace Pt for the purpose of cost reduction as well as retain a comparable activity to Pt/C catalysts [10,11,12] Both Greeley et al [9] and Seo et al [13] found that Pd3–Y/C showed increased ORR activity and stability than Pt/C catalyst. A controlled surface reaction (CSR) method for core–shell catalysts preparation was previously reported by Crabb et al [15,16], this method utilizes the reaction between an organometallic compound and the core metal surface in a hydrogen environment, and the surface composition was well controlled It has the advantage of forming an uniform shell of the second metal on the surface of the core material. A Pd–Pt/C core–shell structure catalyst was included as comparison
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