Enhancing oxygen reduction reaction performance via CNTs/graphene supported iron protoporphyrin IX: A hybrid nanoarchitecture electrocatalyst

Abstract

In spite of disadvantages of limited activity and poor stability, MN4-complexes have created remarkable attention in the scientific community, energy field in particular, due to their applicability in oxygen reduction reaction (ORR) electrocatalysis. These disadvantages can be nullified considerably by using graphene oxide (GO) and carbon nanotubes (CNTs) as carbon supports due to their large surface area and high conductivity. Having limitation of tendency of agglomeration, GO may result to have detrimental effect on the ORR activity of MN4-complexes. In order to suppress the agglomeration of GO, herein, CNTs were effectively utilized. The binary carbon material was loaded with Hemin (H) molecule in a different ratio to form a H@CNTs/rGO composite. The electrochemical results indicated superior activity of H@CNTs/rGO (E1/2 = 89 mV) as compared to H@CNTs (E1/2 = 81 mV), H@rGO (E1/2 = 86 mV) and commercial 20% Pt/C (E1/2 = 84 mV). The characterization data revealed that the addition of CNTs could effectively suppress the agglomeration of rGO, thereby increasing area for the hemin molecule to get adsorbed on both nanocarbons, resulting increment of active sites for ORR. This work opens the opportunities for enhancement of various catalytic performances of metal complexes using nano-carbons.