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(Pt)(-1) at 0.9 V-RHE (13.5-fold higher relative to a commercial Pt/C catalyst), a large electrochemical surface area of 105 +/- 8 m(2) g(Pt)(-1), 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.