PtNi Nanoparticles Encapsulated in Few Carbon Layers as High-Performance Catalysts for Oxygen Reduction Reaction

PtNi alloys have been demonstrated to be one of the most promising catalysts for oxygen reduction reaction (ORR) in fuel cell applications due to their high catalytic activity and efficient utilization of Pt. However, improving the durability of such catalysts remains a significant challenge. Herein, we report on the formation of PtNi nanoparticles with an average diameter of around 10 nm embedded in few carbon layers (PtNi@C) and their ORR catalytic performance. The synthesis procedure entails the use of a solvothermal method to form 2-methylimidazole-Pt-Ni composites with a MOF-like structure (designated as MPN) followed by a thermal annealing treatment. The presence of Pt during the solvothermal process catalyzes the deposition of Ni, and the Ni in the MPN catalyzes the formation of well-graphitized carbon at a temperature as low as 400 degrees C. The PtNi@C catalyst exhibits an ORR mass activity (MA) of 0.84 A mg(pt)(-1) and a specific activity (SA) of 1.54 mA cm(-2) at 0.9 V (vs RHE), representing 6.5-fold and 8.4-fold improvement over a commercial Pt/C catalyst. More significantly, the electrochemically active surface area of the PtNi@C catalyst shows little change after 5000 cycles of potential scans between 0.6 and 1.1 V in O-2-saturated 0.1 M HCIO4. This study demonstrates the feasibility of stabilizing Pt-based nanocatalysts through graphitic carbon encapsulation.