Achieving high volumetric EDLC carbons via hydrothermal carbonization and cyclic activation

Abstract

A novel activation method involving hydrothermal carbonization (HTC) and a pressure-induced low temperature oxidation has been demonstrated for cellulose derived HTC char by using hydrogen peroxide as an active di-oxygen source. The optimized porosity versus gravimetric capacitance results from cellulose derived HTC char synthesized at 220°C. Almost homogeneous and small particle size micro-ellipse/sphere, relatively high surface area and narrow pore size distributions lead to a high bulk density, i.e. 0.73 g cm −3 , of coating-type electrodes, which is much denser than those manufactured from steam-activated carbons for supercapacitor industry, i.e. 0.52 g cm −3 . The resulting carbon prepared herein achieves a relatively high volumetric capacitance in an organic electrolyte-based supercapacitor, reaching a competitive value of an industrial system with the features being environment-friendly, cost-effective as well as high yield, and less energy consumption.

Hydrothermal nitrogen doping of anthracene oil-derived activated carbons for wide voltage asymmetric capacitors

“…The morphology of N-AC-120 is comparable to that of pristine AC, nevertheless there are significant differences when N-AC-180 is considered. This sample seems to have significantly larger particles, which may be due to the increased autogenic pressure experienced (8.8 bars at 180 • C), corroborating previously reported results [37]. High-magnification images of N-AC-120 and N-AC-180 illustrate that their morphology is comparable.…”

Towards Negative Emissions: Hydrothermal Carbonization of Biomass for Sustainable Carbon Materials

“…[161][162][163] Under constant pressure (saturated vapor pressure), according to the reaction temperature, hydrothermal processes can be classified into HTC (180-250 °C), hydrothermal liquefaction (300-350 °C), and hydrothermal gasification (>400 °C). [16,[164][165][166] In the hydrochar produced by HTC, temperature significantly affects the yield, elemental distribution, physical properties, and chemical properties. In a study on BSG by Lorente et al, the yield of hydrochar decreased from 46.92% to 35.46% as the temperature increased from 180 to 250 °C, but the carbon content increased from 59.30% to 71.14%.…”

“…Furthermore, these electrodes achieved a substantial volumetric capacitance enhancement of 13% compared to the industrially used AC. [354] Other researchers have utilized authentic biomass feedstocks as direct precursors for HTC carbon materials. Ren et al employed HTC carbon materials derived from macroalgae (Enteromorpha prolifera) for supercapacitor electrodes.…”

“…[ 161–163 ] Under constant pressure (saturated vapor pressure), according to the reaction temperature, hydrothermal processes can be classified into HTC (180–250 °C), hydrothermal liquefaction (300–350 °C), and hydrothermal gasification (>400 °C). [ 16,164–166 ]…”

Recent research advances of self-discharge in supercapacitors: Mechanisms and suppressing strategies

“…As discussed in the above section, the leakage current, the Faradic reaction and the charge redistribution are responsible for the self-discharge of supercapacitors and have close relation with electrode materials. Up to now, the carbon-based electrode materials have been widely applied in supercapacitors, indicative of the importance of suppressing the self-discharge for carbon-based materials [51][52][53][54]. The extensively used carbon materials are activated carbon (AC), graphene and carbon nanotubes (CNTs) [55][56][57].…”