Ionic Liquid-Derived Ultrafine Pt Nanoparticles with a Uniformly Dispersed State for Long-Life Oxygen Electroreduction

Ultrafine Pt nanoparticles (NPs) homogeneously anchored on hollow carbon nanoshells (PtIL-HCNs) via a wet-chemistry reduction of a new type of imidazolium-[PtCl6]2– ionic liquid (IL) are reported. Confined [PtCl6]2– in IL molecules effectively prevents the growth and spontaneous aggregation of the Pt NPs due to the electrochemical neutrality of the IL, resulting in a homogeneously dispersed state of Pt NPs. The PtIL-HCNs with a Pt loading of 22 wt % outperform the commercial Pt/C (40 wt %) in terms of oxygen reduction reaction (ORR) activity and durability. The half-wave potential of PtIL-HCNs is 51 mV more positive than that of the commercial Pt/C in 0.1 M HClO4. An electrochemical surface area of 97 m2 mg–1 Pt and specific mass activity of 475 mA mg–1 Pt of PtIL-HCNs were found to be 5.6 and 2.7 times higher than those on the commercial Pt/C. Furthermore, this work demonstrates that unlike one-dimensional (1D) carbon nanotubes and two-dimensional (2D) reduced oxide graphene, the three-dimensional (3D) HCN support plays an indispensable role in preventing any stacking of Pt NPs, leading to significantly enhanced ORR activity and durability.