A novel CoN4-driven self-assembled molecular engineering for oxygen reduction reaction.

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-[Co 2 N 8 ]) was synthesized by coordination assembly of CoN 4 macrocyclic moieties on graphene surface. The CoN 4 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-[Co 2 N 8 ]. The results suggested that [CoN 4 ] units are present in self-assembled [Co 2 N 8 ] species. Further, the nanocomposite g-[Co 2 N 8 ] was examined for ORR activity by employing cyclic and linear sweep voltammetry and found that the formal potential (E 1/2) of g-[Co 2 N 8 ] (+0.90 V) was more positive than 20% Pt/C (+0.86 V), indicating a remarkable ORR performance of g-[Co 2 N 8 ] in comparison to 20% Pt/C, followed by 4e-mechanism. Moreover, the nanocomposite (g-[Co 2 N 8 ]) displayed better ORR activity in comparison to [CoN 4 ] complex which can be attributed to the synergistic incorporation of endo and exo N 4 –Co2+ moieties in the [Co 2 N 8 ] species. In addition, g-[Co 2 N 8 ] 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 N 4 -arrangement for various energy related electrocatalysis. [Display omitted] • CoN 4 -complex was synthesized and characterized. • Self-assembly of CoN 4 -complex was carried out using coordination strategy. • Self-assembled molecular catalyst immobilized on graphene synthesized and fully characterized. • Self-assembled molecular catalyst immobilized on graphene exhibited excellent ORR activity. [ABSTRACT FROM AUTHOR]