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

Abstract

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 (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.

Pre‐Oxidating and Pre‐Carbonizing to Regulate the Composition and Structure of Coal Tar Pitch: The Fabrication of Porous Carbon for Supercapacitor Applications

“…[ 23 ] In addition, C─O─C and C─OH groups improve the wettability of carbon, thereby increasing the contact interface between the electrode and electrolyte, thus improving the capacitive performance of porous carbon. [ 24 ] It is still noteworthy that, the presence of a higher amount of C═O (60.86%) in OCZ‐3‐700 is more favorable for the formation of oxygen anion compared to C─O─C and C─OH, which contributes to the formation of a highly conductive and intact electrolyte interfacial phase, thus improve the specific capacitance of the carbon material. [ 25 ] The surface elemental composition of CZ‐3‐700 and OZ‐3‐700 were studied.…”

“…Meanwhile, the high content of heteroatoms provides greater compatibility with the electrolyte by altering the polarity of the graphitic carbon, which greatly improves the wettability of the carbon material, resulting accelerates the electrolyte delivery to the internal transportation of the electrolyte. [ 24 ]…”

Sulfurization of Electrode Material: A Promising Window for Supercapacitor Technology

“…Hydrothermal assembly was employed by D. Wu et al to create sulphur and nitrogen codoped graphene hydrogels. [30] A typical aqueous graphene oxide GO dispersion containing methionine of 30 mg, which has a mass ratio of 0.5 : 1 to GO, was subjected to 30 minutes of sonication. After then, the mixture underwent another 30 minutes of magnetic stirring.…”

Superhydrophobic Flexible Supercapacitors Formed by Integrating Hydrogel with Functional Carbon Nanomaterials

“…[ 1‐3 ] Supercapacitor, which has the advantages of long lifetimes, fast charge/discharge time, and safety, might be a possible solution. [ 4‐5 ] Nevertheless, most of the traditional supercapacitors are heavy and rigid, which are vulnerable to unavoidable damage and interface delamination under mechanical deformations. [ 6‐7 ] Thus, self‐healable supercapacitors are attracting more and more attentions because they can spontaneously restore their energy storage ability even after serious physical damage such as cut‐off.…”