High-surface-area and high-nitrogen-content carbon microspheres prepared by a pre-oxidation and mild KOH activation for superior supercapacitor

Abstract

KOH activation is a well-accepted approach to develop microporosity for porous carbons, but its severe etching reactions could inevitably destroy the structural integrity and diminish the heteroatomic surface chemistry of the resultant carbons. Herein, we report a method to prepare well-defined micro-spherical, high-surface-area and high-nitrogen-doping carbons via a mild KOH activation. The key to our synthesis relies in the pre-oxidation of the nitrogen-rich polymeric microspheres from resorcinol, formaldehyde and melamine, which could enrich nitrogen heteroatoms into the resultant carbonized framework, resulting in the carbon easily activated by KOH with low surface etching and high residual of nitrogen heteroatoms. The obtained carbons possess high specific surface area of 2234-3121 m 2 /g, high nitrogen content of 6.1-12.5 wt. % and well-preserved spherical morphology. When used as the electrodes of supercapacitor, these carbon microspheres could deliver high specific capacitance up to 309 F/g, excellent rate performance and high cyclic performance of 96 % after 5000 cycles in H 2 SO 4 electrolyte. Furthermore, it is found that nitrogen functionalities could contribute considerable pseudo-capacitance, basically through Faradic reactions of the nitrogen.

Enhanced hetero‐elements doping content in biomass waste‐derived carbon for high performance supercapacitor

“…Kesavan et al developed activated carbon materials with high SSA of 1413 m 2 g −1 and capacitance of 381 F g −1 at 1.7 A g −1 by directly KOH activating food waste. Ma et al prepared high SSA (2234 m 2 g −1 ) carbon microspheres by preoxidation and KOH activation of nitrogen‐rich polymeric microspheres, and the materials delivered high capacitance of 309 F g −1 . The capacitance originated from electrostatic adsorption is normally 25 μF cm −2 , so theoretical capacitance of 250 F g −1 can be achieved by one carbon material with high SSA of 1000 m 2 g −1 .…”

Urea‐Modified Phenol‐Formaldehyde Resins for the Template‐Assisted Synthesis of Nitrogen‐Doped Carbon Nanosheets as Electrode Material for Supercapacitors

“…Resin‐based carbon materials are widely applied in supercapacitors . Among them, phenol‐formaldehyde (PF) resins are one of the promising candidates to prepare carbon owing to low price, good shape controllability, especially with high carbon content .…”

KOH activation of coal-derived microporous carbons for oxygen reduction and supercapacitors

“…The mechanism of KOH activation was to react some of the carbon in the raw material with KOH to form some intermediate products such as K 2 CO 3 and K 2 O. 33,34 Aer acid pickling, these intermediate products and excess KOH were washed and then a large number of pores were formed in the etched position. The basic chemical reaction formula was listed as follows:…”