Pyridinic and graphitic nitrogen-rich graphene for high-performance supercapacitors and metal-free bifunctional electrocatalysts for ORR and OER

Abstract

A facile synthesis method to produce nitrogen-doped graphene containing a high atomic percentage of pyridinic N and graphitic N via the thermal annealing of graphene oxide and uric acid is reported. The method yielded N-doped graphene nanosheets that had high surface areas and that contained 9.22 at% nitrogen, which was present in four bonding configurations with a high ratio of pyridinic N and graphitic N. The synthesized N-doped graphene showed excellent capacitance properties, which led to the fabrication of a stacked electrode supercapacitor cell of 2-electrode configuration with a specific capacitance of 230 F g⁻¹ at a current density of 1 A g⁻¹ and with a remarkably high energy density of 62.6 W h kg⁻¹ in aqueous electrolyte. Additionally, this material showed superior properties as an electrocatalyst for both the oxygen-reduction reaction (ORR) and oxygen evolution reaction (OER), producing high current density primarily via the four-electron pathway for ORR at a current density of −4.3 mA cm⁻² and OER activity of a generating current density of 10 mA cm⁻² at 1.74 V vs. RHE in alkaline media. Hence, this dual-natured N-doped graphene could provide a platform for developing nanostructured graphene-based advanced energy storage and conversion devices.