Porous Nitrogen-doped Reduced Graphene Oxide Gels as Efficient Supercapacitor Electrodes and Oxygen Reduction Reaction Electrocatalysts

Summary of main observation and conclusion Heteroatom-doped carbon materials have been widely used in energy storage and conversion such as supercapacitors and electrocatalysts. In this work, L -asparagine (Asn), an amino acid derivative, has been used as a doping agent to prepare nitrogen- doped reduced graphene oxide gels (N-GAs). The 3D interconnected structure gives rise to the superior electrochemical properties for supercapacitor and electrocatalytic oxygen reduction reaction (ORR). The N-GA-4 (the mass ratio of Asn to graphene oxide (GO) is 4 : 1 by hydrothermal method) electrode shows the capacitance of 291.6 F·g –1 at 0.5 A·g –1 . Meanwhile, the assembled symmetric supercapacitor achieves a maximum energy density of 23.8 Wh· kg –1 when the power density is 451.2 W·kg –1 , and demonstrates an ultralong cycling life that the retention of capacitance is 99.3% after 80000 cycles. What's more, the annealed aerogel N-GA-4-900 exhibits an onset potential ( E onset ) of 0.95 V, half wave potential ( E 1/2 ) of 0.84 V (vs. RHE) and the oxygen reduction current density of 5.5 mA·cm –2 at 0.1 V with nearly four-electron transfer, which are superior to commercial Pt/C. This work offers a new insight into the synthesis and applications of N-GAs materials towards high performance in supercapacitors and ORR.