High catalytic activity of Co3O4 nanoparticles encapsulated in a graphene supported carbon matrix for oxygen reduction reaction

Abstract

A simple method, i.e. the calcination of a mixture of Co(NO₃)₂, PEG-PPG-PEG Pluronic® P-123, and melamine in the presence of graphene oxide (GO), has been adopted for the synthesis of Co₃O₄ nanoparticles encapsulated in a graphene supported carbon matrix (Co₃O₄@C/graphene). It shows that the co-existence of P123, melamine, and GO was crucial to obtain the small sized Co₃O₄ nanoparticles encapsulated in the graphene supported carbon matrix. The resulting Co₃O₄@C/graphene was found to be highly active for the oxygen reduction reaction and exhibited higher electrocatalytic activity and better stability than the commercial Pt/C with 20 wt% Pt loading. Their high electrocatalytic activity could be attributed to the synergistic coupling between Co₃O₄ and the nitrogen-doped carbon matrix/graphene, the small Co₃O₄ nanoparticle size, and the presence of the nitrogen doped porous carbon matrix and the carbon encapsulated structure, which make the Co₃O₄@C/graphene kinetically facile and highly stable during complicated electrochemical processes.