Ultrafine Pt-Ni nanoparticles in hollow porous carbon spheres for remarkable oxygen reduction reaction catalysis.

Ultrafine bimetallic Pt-Ni nanoparticles, which catalyze the oxygen reduction reaction (ORR) efficiently, were successfully prepared in hollow porous carbon spheres (HPCSs) under the assistance of organic molecules. 2,2'-Dipyridylamine (dpa) was found to be most effective in preparing homogeneous small Pt-Ni nanoparticles (2.0 ± 0.4 nm) without the phase separation of Pt and Ni during synthesis, and the assistance of the organic molecules was investigated for the alloy nanoparticle formation. The Pt-Ni nanoparticle/HPCS catalyst synthesized in the presence of dpa exhibited remarkable electrochemical performance in the ORR showing a high mass activity of 3.25 ± 0.14 A mg-1Pt at 0.9 VRHE (13.5-fold higher relative to a commercial Pt/C catalyst), a large electrochemical surface area of 105 ± 8 m2 g-1Pt, and high durability. After 60 000 cycles of accelerated durability testing, the mass activity was still 12.3 times higher than that of the commercial Pt/C catalyst.