Trimetallic Au@PdPt core-shell nanoparticles with ultrathin PdPt skin as highly stable electrocatalysts for the oxygen reduction reaction in acid solution

To design efficient and low-cost core-shell electrocatalysts with an ultrathin platinum shell, the balance between platinum dosage and durability in acid solution is of great importance. In the present work, trimetallic Au@PdPt core-shell nanoparticles（NPs）with Pd/Pt molar ratios ranging from 0.31:1 to 4.20:1 were synthesized based on the Au catalytic reduction strategy and the subsequent metallic replacement reaction. When the Pd/Pt molar ratio is 1.19:1(designated as Au@Pd1.19 Pt1 NPs), the superior electrochemical activity and stability were achieved for oxygen reduction reaction（ORR） in acid solution. Especially, the specific and mass activities of Au@Pd1.19 Pt1 NPs are 1.31 and 6.09 times higher than those of commercial Pt/C catalyst. In addition, the Au@Pd1.19 Pt1 NPs presented a good durability in acid solution. After 3000 potential cycles between 0.1 and 0.7 V（vs. Ag/AgCl）, the oxygen reduction activity is almost unchanged. This study provides a simple strategy to synthesize highperformance trimetallic ORR electrocatalyst for fuel cells.