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

Abstract

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⁻¹_Pt at 0.9 V_RHE (13.5-fold higher relative to a commercial Pt/C catalyst), a large electrochemical surface area of 105 ± 8 m² g⁻¹_Pt, 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.