CoFe Nanoalloys Encapsulated in N-Doped Graphene Layers as a Pt-Free Multifunctional Robust Catalyst: Elucidating the Role of Co-Alloying and N-Doping

Pt is known to be a state-of-the-art catalyst for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER), while it can also be used for the hydrogenation of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The quest is ongoing to find a suitable catalyst to circumvent the problems associated with the precious metal Pt. Here, we report a facile and green strategy to fabricate CoFe nanoalloys encapsulated in N-doped graphene layers (CoxFe1-x@N-G) by pyrolysis and their catalytic activity toward ORR, HER, and hydrogenation of 4-NP. Intensive studies have been carried out to elucidate the roles of alloying and N-doping. The catalytic activity is found to improve with increasing amounts of Co in the CoFe core and N-doping in the graphene layers. A similar onset potential with better current density as compared to the state-of-the-art Pt/C catalyst in alkaline medium has been achieved for CoxFe1-x@N-G toward ORR activity. These catalysts also show efficient and highly stable HER activity and are very efficient and magnetically separable in the hydrogenation of 4-NP to 4-AP. Overall, the non-precious-metal alloy nanostructures can be exploited as multifunctional catalysts in fuel cells, hydrogen storage systems, and wastewater treatment.