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[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, H-1 NMR and C-13 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 (E-1/2) 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 nano composite (g-[Co2N8]) displayed better ORR activity in comparison to [CoN4] complex which can be attributed to the synergistic incorporation of endo and exo N-4-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 N-4-arrangement for various energy related electrocatalysis. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

A nanocomposite (g-[Co2N8]) with excellent ORR performance was synthesized by coordinating CoN4 macrocyclic moieties on the graphene surface, outperforming 20% Pt/C catalyst and showing good stability. This work provides insights for designing multi-metallic coordination polymers for energy-related electrocatalysis involving different metal ions in N-4-arrangement.