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

摘要

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 nitrogendoped 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 80 000 cycles.What's more,the annealed aerogel N-GA-4-900 exhibits an onset potential (Eonset) of 0.95 V,half wave potential (E1/2) 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.