Insight into hydroxides-activated coals: Chemical or physical activation?

Alcañiz-Monge, Juan; Illán-Gómez, M.J.

doi:10.1016/j.jcis.2007.10.017

Cited by 39 publications

(27 citation statements)

References 34 publications

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“…The increase of the O/C ratio with W is due to the carbon oxidation by CO 2 produced from K 2 CO 3 decomposition, the latter being formed in situ. KOH activation has indeed been described as a combined chemical-physical activation [29]. values of the measurements.…”

Section: Elemental Analysismentioning

confidence: 99%

Assessment of hydrogen storage in activated carbons produced from hydrothermally treated organic materials

Schaefer

Fierro

Izquierdo

et al. 2016

International Journal of Hydrogen Energy

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Available online xxx Keywords:Hydrogen storage Adsorption Hydrothermal carbonisation KOH activation Microporous activated carbons a b s t r a c t 12 activated carbons (ACs) were prepared by KOH activation using hydrochars as precursors. These hydrochars were prepared by hydrothermal carbonisation (HTC) of sucrose solutions at concentrations ranging from 0.2 to 1.6 mol L À1 . The KOH to hydrochar weight ratio (W) was varied from 1 to 5, and the activation temperature was set to 1023 K. ACs texture was assessed by nitrogen and carbon dioxide adsorption at 77 and 273 K, respectively; pore size distribution was calculated by using both isotherms and the SAIEUS© software. ACs with surface areas between 790 and 2240 m 2 g À1 were obtained. Hydrogen excess adsorption was determined at 298 K and pressures up to 10 MPa in a volumetric device, and the isosteric heat of adsorption (Q st ) was calculated for four ACs, using hydrogen isotherms obtained at 278, 298 and 308 K. Potassium intercalation between graphitic planes was assumed to account for the high Q st values, 7e8 kJ mol À1 . Hydrogen uptake at 2 MPa was compared with hydrogen adsorption data of 38 other ACs reported in the open literature. Hydrogen adsorption fundamentally depends on micropore volume and preliminary HTC did not enhance hydrogen storage although it could be a good strategy for doping carbon with heteroelements.

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Section: Elemental Analysismentioning

confidence: 99%

Assessment of hydrogen storage in activated carbons produced from hydrothermally treated organic materials

Schaefer

Fierro

Izquierdo

et al. 2016

International Journal of Hydrogen Energy

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“…V mi /V tot of RH-K2N1.5 and RH-K2N1 (82.8% and 90.0%) are higher than those of RH-K1.5N2 and RH-K1N2 (84.6% and 76.7%). According to Alcaniz-Monge and Illan-Gomez [20], the development of microporosity is due to carbon gasification and the metal intercalation, and only KOH generates supermicroporosity.…”

Section: Resultsmentioning

confidence: 99%

Preparation of Pore-Size Controllable Activated Carbon from Rice Husk Using Dual Activating Agent and Its Application in Supercapacitor

Ван

Thu

2019

Journal of Chemistry

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Activated carbons prepared from rice husk by chemical activation with dual activation agents, KOH and NaOH, have been studied and characterized by BET, SEM, EDX, FTIR, Boehm titration, Raman, and TGA. It was found that the KOH/NaOH impregnation ratio plays an important role on textural properties of AC. At the same amount of total alkali hydroxide, the KOH/NaOH ratio higher than 1.33 resulted in larger specific surface area (2990∼3043 m2·g−1), microporous surface area (2747∼2831 m2·g−1), and higher micropore volume (1.4250∼1.4316 cm3·g−1). The as-prepared samples exist in the form of spherical-shaped particles with the size ranging from 20 to 60 nm and contain numerous surface functional groups. The as-prepared activated carbons were then assessed as an electrode material of supercapacitor operating in the 0.5 M K2SO4 electrolyte in potential windows of −1.0∼0.0 V. The highest capacitance obtained was 205 F·g−1 at the scan rate of 2 mV·s−1 and 225 F·g−1 at a current density of 0.2 A·g−1. At the scan rate as high as 50 mV·s−1, all the as-prepared activated carbons in this study have the specific capacitance greater than 100 F·g−1.

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“…The specific surface area initially rapidly increased with the increase in KOH solution concentration and increased more slowly roughly after the concentration exceeded 2 M. It reached 2549 m 2 /g at a concentration of 4.5 M. The mechanism of reaction of activation with KOH has been explained in several different ways by various researchers [14][15][16][17][18] . Using common factors presented in all their articles, Sakazaki et al proposed the following reaction formulas [7] .…”

Section: Resultsmentioning

confidence: 99%

Effects of Activation with CO<sub>2</sub>/KOH on the Pore Structures of Coffee Grounds-derived Carbon

Kikuchi

Yamashita

Sakuragawa

2012

Trans. Mat. Res. Soc. Japan

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In this study, coffee grounds were carbonized through activation with carbon dioxide (hereinafter referred to as CO 2 ) or potassium hydroxide (hereinafter referred to as KOH), and the effects of the respective activation conditions on the pore structures of the carbon obtained were investigated. The specific surface area of the sample carbonized in a CO 2 stream at 850˚C was 752 m 2 /g and that of the sample impregnated with KOH and carbonized was 2549 m 2 /g when the concentration of KOH was 4.5 M. In the sample carbonized in a CO 2 stream, the pores formed were 0.8, 1, and 3.1 nm in size, which were enlarged with the increase in treatment temperature and started to include numerous mesopores. In the sample impregnated with KOH and carbonized, the pores formed were 0.7 nm and 1 to 1.1 nm in size, which were slightly enlarged with the increase in concentration of KOH. It was confirmed that for coffee grounds, activation with KOH had an effect of increasing specific surface area and that CO 2 activation had an effect of increasing pore size.

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Insight into hydroxides-activated coals: Chemical or physical activation?

Cited by 39 publications

References 34 publications

Assessment of hydrogen storage in activated carbons produced from hydrothermally treated organic materials

Assessment of hydrogen storage in activated carbons produced from hydrothermally treated organic materials

Preparation of Pore-Size Controllable Activated Carbon from Rice Husk Using Dual Activating Agent and Its Application in Supercapacitor

Effects of Activation with CO<sub>2</sub>/KOH on the Pore Structures of Coffee Grounds-derived Carbon

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