Engineering of activated carbons (ACs) through chemical activation of organic precursors has been extensively studied for a wide variety of biopolymers, biomasses, wastes and other fossil-based precursors. Despite huge efforts to engineer evermore performant and sustainable ACs, “searching-for-the-best-recipe” type of studies are more the rule than the exception in the published literature. Emerging AC applications related to energy and gas storage require strict control of the AC properties and a better understanding of the fundamentals underlying their engineering. In this study, we provide new insights into the K2CO3 chemical activation of plant-based polyphenols—lignins and tannins—through careful thermoanalytical and structural analyses. We showed for the the first time that the reactivity of polyphenols during K2CO3 chemical activation depends remarkably on their purity and structural properties, such as their content of inorganics, OH functionalities and average molecular weight. We also found that the burn-off level is proportional to the K2CO3/ lignin impregnation ratio (IR), but only within a certain range—high impregnation ratios are not needed, unlike often reported in the literature. Furthermore, we showed for the first time that the K2CO3 chemical activation of different carbon surfaces from lignins and tannins can be modelled using simple global solid-state decomposition kinetics. The identified activation energies lay in the range of values reported for heterogenous gas-carbon surface gasification reactions ( O2-C, H2O- C, or CO2- C) in which the decomposition of C(O) surface complexes is the common rate-limiting step.

This research aims to study the effect of impregnation ratio and activation temperature on microporous development of activated carbon (AC). Rubberwood chips, which are wasted from home furnishing industry, were used as precursors for synthesized of activated carbon by chemical activation employing Potassium hydroxide (KOH) as activation agent. Rubberwood char was carbonized at 400 °C for 1 h under inert gas. In this experiment, the rubberwood chars were impregnated with KOH solution by 1:1–3 (char: KOH) impregnation ratio for 24 h, then the samples were activation at 600–800 °C. Surface area, pore volume, micropore volume, pore size distribution, adsorption isotherm and porous structure were analyzed in this experiment to identify the properties of derived activated carbon. According to the investigation, the activated carbon, activated at 800 °C with impregnation ratio of 1:3, demonstrated the highest surface area, pore volume and micropore volume as 1491.75 m2/g, 0.6777 cm3/g, and 0.5813 cm3/g, respectively. Its average pore size was 1.82 nm and it also showed type I adsorption isotherm which indicates as microporous solid.

Biomass of agricultural waste is getting increasing attention all over the world as it is a kind of renewable, abundantly available, low cost, and environmentally friendly resource. Preparation of activated carbon from agricultural waste via microwave-assisted chemical agent activation. The porosity, surface area, and functional and surface chemistry were featured by means of low-temperature nitrogen adsorption, Scanning Electron Microscopy, (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). The best conditions resulted in activated carbon with adsorption capacity of 517.5 mg/g and carbon yield of 80.99%. The activated carbons from carbonized tobacco stem with K2CO3 activation by microwave radiation is highest of surface area, and total pore volume corresponded to 2557 m2/g, and 1.647 cm3/g, respectively, with a high contribution of mesopores, microwave power of 700 W, and irradiation time of 30 min. The results of the review showed that chemical activation could develop both microporosity and mesoporosity. The findings support the potential to prepare high surface area and micropore-activated carbon from agricultural waste by microwave-induced chemical activation.

A carbon nanofiber was produced from the Areca catechu husk as a supercapacitor electrode, utilizing a chemical activation of potassium hydroxide (KOH) at different concentrations. One-stage integrated pyrolysis both carbonization and physical activation were employed for directly converting biomass to activated carbon nanofiber. The morphology structure, specific surface area, pore structure characteristic, crystallinity, and surface compound were characterized to evaluate the influence on electrochemical performance. The electrochemical performance of the supercapacitor was measured using cyclic voltammetry (CV) through a symmetrical system in 1 M H2SO4. The results show that the KOH-assisted or absence activation converts activated carbon from aggregate into a unique structure of nanofiber. The optimized carbon nanofiber showed the large specific surface area of 838.64 m2 g−1 with the total pore volume of 0.448 cm3 g−1, for enhancing electrochemical performance. Beneficial form its unique structural advantages, the optimized carbon nanofiber exhibits high electrochemical performance, including a specific capacitance of 181.96 F g−1 and maximum energy density of 25.27 Wh kg−1 for the power density of 91.07 W kg−1. This study examines a facile conventional route for producing carbon nanofiber from biomass Areca catechu husk in economical and efficient for electrode supercapacitor.

In this study, hair waste was converted into active carbon for the first time and its characteristics were analyzed. As chemical activation tool, zinc chloride ( ZnCl2) was impregnated and then carbonized under different temperatures (250–300 °C). Scanning Electron Microscope (SEM) images showed an increase in the pore density, radius and volume of pores. X-ray diffraction analysis (XRD) showed that the samples had an amorphous structure. In Fourier-transform infrared (FT-IR) spectroscope analysis, C=C and N–H vibrations observed in 1515–1520 cm−1 wave number of protein molecules were found to disappear with the increase in temperature. With Raman spectroscopy, the behaviors of D peak at 1344 cm−1 wave number and G peak at 1566 cm−1 wave number expressing structure layout in carbonized structures were analyzed depending on the temperatures. Between these intensities, (ID/IG) the rate was found to differ in direct proportion to temperature. XRD spectrums showed that the samples are converted into a more irregular crystal structure. All these results implied that the waste hair mass could be used as an adsorbant material.

Low thermal conductivity carbon fibers from polyacrylonitrile (PAN) are currently being explored as an alternative for traditional rayon-based carbon fibers with a thermal conductivity of 4 W/m K. Compared to multiple component electrospinning, this research demonstrated another feasible way to make low thermal conductivity carbon fibrous material by electrospinning PAN followed by carbonization and alkali activation. The effects of activation condition on microstructure, pore formation, and thermal conductivity of the resultant carbon nanofibrous material were investigated. The processing-structure-thermal conductivity relationship was revealed and mechanism of thermal conductivity reduction was discussed. The overall thermal conductivity of the prepared carbon nanofibrous material is a result of combined effects from factors of carbon structure and number of pores rather than volume of pores or specific surface area. The activated carbon nanofibrous materials showed thermal conductivity as low as 0.12 W/m K, which is a reduction of ~ 99% when compared to that of solid carbon film and a reduction of ~ 95% when compared to that of carbon nanofibrous material before activation.

A highly functional, environmentally friendly carbonaceous adsorbent material using black liquor (a by-product from the pulp manufacturing) was produced and characterized. This study showed the effect of self-chemical activation driven by inherent alkali, originated from the unique composition of black liquor. A preparation of the micropore-dominant activated carbon was made in an easy and simple manner. The specific surface areas of samples were found to be 718–1591 m2/ g variated upon heat treatment conditions. The sample activated at 850 °C (50 min as retention time) showed the maximum specific surface area of 1591 m2/ g with 13.6% as a production yield. Considering the factors influencing pore structure of activated carbon materials in this study, it was confirmed that mesopore-related surface area increased gradually as the activation temperature and retention time increased. It is noteworthy to address that economically valuable micropore-dominant activated carbon can be produced by a simple heat treatment of the waste material, black liquor. The activated carbon sample derived from black liquor can be applied to various fields, such as environment and energy storage.

In this study, several kinds of active carbons with high specific surface area and micro pore structure were prepared from the coconut shell charcoal using chemical activation method. The physical property of prepared active carbon was investigated by experimental variables such as activating chemical agents to char coal ratio, flow rate of inert gas and temperature. It was shown that chemical activation with KOH and NaOH was successfully able to make active carbons with high surface area of 1900~2500 m2/g and mean pore size of 1.85~2.32 nm. The coin cell using water-based binder in the electrolyte of LiPF6 dissolved in mixed organic solvents (EC:DMC:EMC=1:1:1 vol%) showed better capacity than that of oil-based binder. Also, it was found that the coin cell of water-based binder shows an improved cycling performance and coulombic efficiency.

A novel electrode for an NO gas sensor was fabricated from electrospun polyacrylonitrile fibers by thermal treatment to obtain carbon fibers followed by chemical activation to enhance the activity of gas adsorption sites. The activation process improved the porous structure, increasing the specific surface area and allowing for efficient gas adsorption. The gas sensing ability and response time were improved by the increased surface area and micropore fraction. High performance gas sensing was then demonstrated by following a proposed mechanism based on the activation effects. Initially, the pore structure developed by activation significantly increased the amount of adsorbed gas, as shown by the high sensitivity of the gas sensor. Additionally, the increased micropore fraction enabled a rapid sensor response time due to improve the adsorption speed. Overall, the sensitivity for NO gas was improved approximately six-fold, and the response time was reduced by approximately 83% due to the effects of chemical activation.

OXI-PAN fibers, Kynol fibers and rayon fibers were used as precursorsfor the preparation of activated carbon fibers (ACFs) by chemical activation with KOH at 800℃. The effects of different precursorfibers and fiber/KOH ratios on the final ACFs are discussed. The precursor fibers used are appropriate for the ACFs in a single stage pyrolysis process. The OXI-PAN fibers which were activated with KOH of 2.0M showed a specific surface area of 2328m2/g however, loosed the fiber shape because of low yields. The Kynol fibers and Rayon fibers showed the high yields but the lower specific surface area of 900m2/g and 774m2/g, respectively, at KOH of 1.5M. The OXI-PAN fibers which were activated with KOH of 1.5M have a specific surface area of 1028m2/g and higher micro-pore volumes and lower yields rather than Kynol-1.5 and Rayon-1.5 samples. This phenomenon is because of higher chemical resistance of the Kynol and Rayon fibers rather than OXI-PAN fibers. However, the Kynol fibers were the best precursors on KOH activation at 800℃ considered carbon yields, surface areas and micropore volumes.

Granular Activated Carbon (GAC) has been proven to be an excellent material for many industrial applications. A systematic study has been carried out of the kinetics of physical as well as chemical activation of phenolic resin chars. Physical activation was carried out using CO2 and chemical activation using KOH as activating agent. There are number of factors which influence the rate of activation. The activation temperature and residence time at HTT varied in the range 550~1000℃ and ½~8 hrs respectively. Kinetic studies show that the rate of chemical activation is 10 times faster than physical activation even at much lower temperature. Above study show that the chemical activation process is suitable to prepare granular activated carbon with very high surface area i.e. 2895 m2/g in short duration of time i.e. 1 to 2 hrs at lower temperature i.e. 750℃ from phenolic resins.

Naphtha cracking bottom oil was reformed with heat treatment and then spun at 310℃. These pitch-based carbon fibers were carbonized at 1000℃ after oxidation at 280℃, for 90 min. These fibers were chemically activated with molar ratio of KOH/CF (1 : 1) at different temperatures (250~900℃) for 1 hr. The process of activation was characterized with DTA, TGA, BET surface area and pore size distribution. The activation of fibers by KOH was performed by several process. One is the reduction process that carbon fiber was reacted with K2O produced from dehydration process above 400℃. The other is the process that K2CO3 was directly reacted with carbon fiber. At 800℃, the activation was performed by catalyzed mechanism that K2O was obtained from the reaction of metal potassium with CO2, then was changed to K2CO3. At 870℃, the activation was also observed that activation mechanism was promoted by metal catalyst with CO2 from decomposition of K2CO3. The specific surface area of prepared activated carbon fibers was dependent on the activation mechanism. The specific surface area was in the range of 1519~2000 cm3/g and was the largest prepared at 870℃. The pores developed were mostly micropores which was very narrow and uniform. The total pore volume was 0.58~0.77 cm3/g.