Simultaneous doping of nitrogen and fluorine into reduced graphene oxide: A highly active metal-free electrocatalyst for oxygen reduction

Abstract Reduced graphene oxide co-doped with nitrogen and fluorine (N–F/rGO) was successfully prepared by a simple one-step thermal annealing process using a mixture of graphene oxide and ammonium fluoride in an argon atmosphere. X-ray photoelectron spectroscopy demonstrated that the nitrogen and fluorine atoms were successfully doped into the rGO structure at atomic percentages of 2.51 and 0.74, respectively. Nitrogen adsorption–desorption measurement revealed that the as-prepared N–F/rGO has a high surface area (412 m2 g−1) with numerous slit-shaped pores (1.60 cm3 g−1). The electrocatalytic activity of N–F/rGO for oxygen reduction reaction was found to be higher than that of rGO doped only with nitrogen (N/rGO); in fact, it was comparable to the activity of conventional commercial Pt/C in an alkaline electrolyte. In addition, the catalyst exhibited excellent long-term stability/durability, good methanol tolerance, and high selectivity for the four-electron transfer pathway. A possible mechanism is suggested for the improvement conferred by fluorine.