Highly Efficient Oxygen Reduction Reaction Activity of Graphitic Tube Encapsulating Nitrided CoxFe gamma Alloy

Abstract

Nonprecious metals are promising catalysts to avoid the sluggish oxygen reduction reaction (ORR) in next-generation regenerative fuel cells or metalair batteries. Therefore, development of nonprecious metal catalysts for ORR is highly desirable. Herein, precise tuning of the atomic ratio of Fe and Co encapsulated in melamine-derived nitrogen-rich graphitic tube (NGT) is reported. The Co1.08Fe3.34 hybrid with metal. nitrogen bonds (1: Co1.08Fe3.34@ NGT) shows remarkable ORR catalytic activities (80 mV higher in onset potential and 50 mV higher in half-wave potential than those of state-ofthe- art commercial Pt/C catalysts), high current density, and stability. In acidic solution, 1 also shows compatible performance to commercial Pt/C in terms of ORR activity, current density, stability, and methanol tolerance. The high ORR activity is ascribed to the co-existence of Fe-N, Co-N, and sufficient metallic FeCo alloys which favor faster electron movement and better adsorption of oxygen molecules on the catalyst surface. In the alkaline anion exchange membrane fuel cell setup, this cell delivers the power density of 117 mW cm(-2), demonstrating its potential use for energy conversion and storage applications.