N-Doped and Sulfonated Reduced Graphene Oxide Supported PtNi Nanoparticles as Highly Efficient Electrocatalysts for Oxygen Reduction Reaction

N-doping and sulfonation is prepared on the reduced graphene oxide (rGO) support for PtNi nanoparticles (PtNi/S-(N)rGO) by a simple method of hydrothermal synthesis and thermal decomposition. The specific surface area increases from 180.7 m2/g of PtNi/rGo to 293.5 m2/g of PtNi/S-(N)rGO. The surface morphology shows wrinkles sites, which are separated by the sulfonated groups. The catalytic stability and efficiency are improved by the anchoring effect of sulfonated groups and evenly distribution of nanoparticles, respectively. The synergistic effect of N-doping and sulfonation can be in favor of catalytic efficiency by the increase of number of electron transfer. The half-wave potential of the PtNi/S-(N)rGO catalyst is up to 0.632 V, a small positive shift compared to the Pt/C catalyst. The durability of the PtNi/S-(N)rGO is 2.6 times higher than of the Pt/C catalyst after 5000 repeated cycles. The peak power of the PtNi/S-(N)rGO catalyst increased 37.5% compared to the Pt/C catalyst. Therefore, the stability and catalytic efficiency are improved by the PtNi/S-(N)rGO catalyst applied in proton exchange membrane fuel cell (PEMFC) compared to the commercial Pt/C catalyst.