Nitrogen-doped hierarchically structured porous carbon as a bifunctional electrode material for oxygen reduction and supercapacitor

Development of an efficient electrode material with robust porous architecture, high catalytic activity and excellent electrochemical performance toward both oxygen reduction reaction (ORR) and supercapacitor is extremely important. Herein, a facile route to fabricate nitrogen-doped hierarchical porous carbon (NHPC) materials as a bifunctional electrode material for ORR and supercapacitors is presented. The as-prepared NHPC-0.5 integrate the feature of high-level nitrogen-doping (12.1 at %), large specific surface area (up to 1798.4 m2 g−1) and hierarchical multi-pores of cross-linked micro and mesoporous channels. When used as ORR electrocatalyst, the NHPC-0.5 demonstrated highest selectivity (four-electron transfer process), high activity (half-wave potential 0.883 V vs. RHE, initial potential 1.004 V vs. RHE) and favorable tolerance against methanol. When tested its application in zinc-air batteries, its maximum output power density was 25.1  mW cm−2, and delivers a superior durability of negligible potential loss after 100 cycles. When applied in supercapacitor, the NHPC-0.5 can deliver a high specific capacitance of 283.7 F g−1 at current density of 1 A g−1 in 1 M H2SO4 electrolyte, and outstanding cyclic stability (105.8% capacitance retention after 40,000 cycles). Moreover, a symmetric supercapacitor (NHPC-0.5//NHPC-0.5) can release an energy density of 11.3 W h kg−1 at the power density of 502 W kg−1. The encouraging results of this work may provide a new perspective to construct N-doped hierarchical porous carbon materials in energy storage devices with excellent electrochemical performance.