Abstract
The poor kinetics of oxygen reduction reaction (ORR) invites a quest for the development of low-cost and efficient non-Pt electrocatalysts for fuel cells. Herein, a nanocomposite (g-[Co2N8]) was synthesized by coordination assembly of CoN4 macrocyclic moieties on graphene surface. The CoN4 macrocyclic complex was characterized by UV–Vis, FT-IR, Mass, 1H NMR and 13C NMR spectral studies, whereas UV–Vis, FT-IR, and Mass spectral, Raman, XRD and TEM studies were utilized to characterize the nanocomposite g-[Co2N8]. The results suggested that [CoN4] units are present in self-assembled [Co2N8] species. Further, the nanocomposite g-[Co2N8] was examined for ORR activity by employing cyclic and linear sweep voltammetry and found that the formal potential (E1/2) of g-[Co2N8] (+0.90 V) was more positive than 20% Pt/C (+0.86 V), indicating a remarkable ORR performance of g-[Co2N8] in comparison to 20% Pt/C, followed by 4e-mechanism. Moreover, the nanocomposite (g-[Co2N8]) displayed better ORR activity in comparison to [CoN4] complex which can be attributed to the synergistic incorporation of endo and exo N4–Co2+ moieties in the [Co2N8] species. In addition, g-[Co2N8] electrocatalyst exhibited a comparable stability to 20% Pt/C catalyst after 5000 cycles. This work will help to design multi-metallic coordination polymers with similar or different metal ions in N4-arrangement for various energy related electrocatalysis.
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