Platinum-Palladium Core–Shell Nanoflower Catalyst with Improved Activity and Excellent Durability for the Oxygen Reduction Reaction

In this work, highly active and stable platinum–palladium core–shell nanoflowers supported on sulfur-doped graphene (PtPd-NF/SG) with a polyol reduction method are synthesized. Platinum is decorated on palladium seeds to form core–shell structured floral petals to improve surface activity and give high electrochemically active surface area and stability. The catalyst is deposited on sulfur-doped graphene to induce highly favorable catalyst-support interactions to ensure long-term electrochemical stability. The specific activity and mass activity of the synthesized core–shell nanocatalysts are 3.2 and 4.7 times higher than commercial Pt/C toward oxygen reduction reaction, respectively. After 10 000 testing cycles, the mass and specific activity of the catalyst is ≈25 and ≈18 times higher than the Pt/C benchmark catalyst, respectively. The enhanced electrochemical activity and excellent stability of PtPd-NF/SG can be attributed to the 2D core–shell nanoflower structure, weak binding of hydroxyl groups to the platinum metal deposited on palladium, and robust sulfur-doped graphene support.