Thermochemical Activation Research Articles

PRODUCTION OF HIGH-PERFORMANCE SUPERCAPACITOR ELECTRODES BASED ON GRAPHENE-LIKE CARBON OBTAINED FROM TEA WASTE

This article presents the results of a study on the production of active material for supercapacitor electrodes from graphene-like carbon obtained from tea waste, carbonization at a temperature of 550°C, followed by thermochemical activation using potassium hydroxide in a ratio of 1:4 at a temperature of 850°C in a quartz tube furnace. The structure and morphology of the resulting porous graphene-like carbon based on tea waste were investigated using scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), X-ray diffraction, and Raman spectroscopy. The surface area of activated porous graphene-like carbon from tea waste was 2407 m2/g. Electrochemical characterization of the assembled supercapacitor using GLC-TW was performed on an Elins P-40X electrochemical workstation and showed high specific capacitance values of 182 F/g, as well as a Coulombic efficiency of 96% at a current density of 1 A/g and the material also demonstrated a low charge transfer resistance of about 1.5 Ohms. These results highlight the effectiveness of using graphene-like carbon derived from tea waste, demonstrating its potential as a promising material for supercapacitors.

Effect of thermochemical activation temperature on electrical conductivity and concentration of charge carriers in the obtained porous carbon materials

Effect of thermochemical activation temperature on electrical conductivity and concentration of charge carriers in the obtained porous carbon materials

Magnetic activated carbonaceous materials from sugarcane bagasse: Preparation, characterization, and hexavalent chromium removal

The presence of hexavalent chromium (Cr (VI)) in effluents remains a global concern due to its toxic properties. Even though adsorption has been employed for its removal from water, developing sustainable materials with higher adsorption capacities is still pivotal to tackling such contamination. In this study, two magnetic carbons (MC) were produced by hydrothermal carbonization (HTC) of sugarcane bagasse in the presence of iron (III) nitrate at 230 and 270 °C. Both MCs were thermochemically activated at 500 and 700 °C using KOH (1:2; w:w). The materials were characterized in terms of composition, structure, morphology, texture, and surface properties and then evaluated in adsorption studies of Cr (VI). After HTC, some iron phases such as α-Fe2O3, γ-Fe2O3, and Fe3O4 were observed, while thermochemical activation additionally revealed Fe0 and Fe4[Fe(CN)6]3. Activation increased the amount of meso- and macropores, specific surface area, pHzpc, surface hydrophilicity, and carbon and nitrogen contents. The adsorption kinetics study indicated that the pseudo-second-order model describes better the behavior of the materials. The investigation of adsorbent dose showed that doses below 1.00 g L−1 were more efficient in Cr (VI) removal. MC-230 and MC-270 thermochemically activated at 700 °C exhibited the highest Cr (VI) adsorption capacities (10.5 and 15.5 mg g−1, respectively). Therefore, the improved adsorption capacity for Cr (VI) of the materials thermochemically activated at 700 °C was mainly due to their enhanced textural properties.

PREPARATION OF THERMOCHEMICALLY ACTIVATED CARBON ADSORBENTS BASED ON COTTON STEM AND COTTON SHELL AND THEIR IR SPECTROSCOPY ANALYSIS

This article discusses the practical importance of adsorbents today, areas of application, and methods of obtaining activated carbon adsorbents based on local raw materials. Preparation of adsorbents activated by the method of thermochemical activation based on cotton stalks and cotton bolls, functional groups in the obtained adsorbents were analyzed by IR spectroscopy.

Preparation of highly effective carbon adsorbents based on high-moor peat from the European North of Russia

The study of active coals obtained from high-moor peat of the European North of Russia was conducted by method of thermochemical activation with NaOH with various types of pre-treatment (debituminization and pre-hydrolysis). Based on the results of the low-temperature adsorption of nitrogen, the derived active coals belong to the adsorbents in which the structure of the micro-agents predominates. The specific surface of the coal pores reaches 2330 m2/g, the total volume of pores – 1.44 cm3/g. It has been determined that the introduction of the pre-hydrolysis stage makes it possible to increase significantly the yield of active coals. For initial peat samples, the growth is 28%; for debituminized – 97%, moreover it significantly improve its sorption characteristics. It has been shown that weakly decomposed peat of the European North of Russia can be used as raw material for producing high-efficiency carbon microporous adsorbents.

Activated biomass-derived 3-dimensional porous graphene-like carbon for high-performance energy storage electrode materials

This article reports studies on the fabrication of active material for supercapacitor electrodes, from 3D porous graphene-like carbon (GLC), synthesized by carbonization from coffee waste (CW) and tea waste (TW) at 550 °C, followed by thermochemical activation in KOH at 850 °C in a quartz tubular furnace. The microstructure of coffee and tea waste shows the form of micro- and mesopores during carbonization and further chemical activation forms hierarchically highly porous 3D graphene-like carbon. GLC-CW exhibited a higher specific surface area (SSA) of 3486 m2/g according to the Brunauer-Emmett-Teller (BET) method, compared to GLC-TW, which had an SSA of 2407 m2/g. These results highlight the effectiveness of graphene-like carbon derived from coffee and tea waste, demonstrating its potential as a promising material for high-capacity supercapacitors. The electrochemical characteristics of the assembled supercapacitors using GLC-CW and GLC-TW revealed significantly higher specific capacitance values of 214 F/g and 182 F/g respectively, along with cycling stability of 98 % and 95 % during 5000 cycles of charge and discharge at 2 A/g current density. This approach can produce high-performance electrode materials for supercapacitors at a reasonable cost and with easy scalability.

Synergetic studies on the thermochemical activation and polyaniline integration on the adsorption properties of natural coal for chlorpyrifos pesticide: steric and energetic studies

Three types of synthetic coal-derived adsorbents were characterized as potential enhanced structurers during the removal of chlorpyrifos pesticide. The raw coal (CA) was activated into porous graphitic carbon (AC), and both CA and AC were blended with polyaniline polymers (PANI/CA and PANI/AC) forming two advanced composites. The adsorption performances of the modified structures in comparison with CA were evaluated based on both the steric and energetic parameters of the applied advanced isotherm model (the monolayer model of one energy). The uptake performances reflected higher capacities for the PANI hybridized form (235.8 mg/g (PANI/CA) and 309.75 mg/g (PANI/AC) as compared to AC (156.9 mg/g) and raw coal (135.8 mg/g). This signifies the impact of activation step and PANI blending on the surface and textural properties of coal. The steric investigation determined the saturation of the coal surface with extra active sites after the activation step (Nm(AC) = 62.05 mg/g) and the PANI integration (Nm(PANI/CA) = 113.5 mg/g and Nm(PANI/AC) = 169.7 mg/g) as compared to raw coal (Nm(CA) = 39.6 mg/g). This illustrated the reported uptake efficiencies of the modified samples, which can be attributed to the enhancement in the surface area and the incorporation of additional chemical groups. The results also reflect that each site can be loaded with 3–4 molecules of chlorpyrifos, which are arranged vertically and adsorbed by multi-molecular mechanisms. The energetic studies (< 40 kJ/mol) suggested the physical uptake of pesticide molecules by dipole bonding and hydrogen bonding processes. The thermodynamic functions donate the exothermic properties of 47reactions that occur spontaneously.

Investigation of the applicability of activated carbon obtained by thermochemical activation of hydrolytic lignin with sodium hydroxide as an electrode material of a supercapacitor

Investigation of the applicability of activated carbon obtained by thermochemical activation of hydrolytic lignin with sodium hydroxide as an electrode material of a supercapacitor

Preparation of lignin-based porous carbon through thermochemical activation and nitrogen doping for CO2 selective adsorption

Preparing CO2 adsorbents from biomass feedstock has garnered considerable attention due to its potential for fostering sustainable, economic, and eco-friendly development. Introduction of nitrogen-containing functional groups can enhance the affinity for CO2 of biochar but also inevitably affect the pore structure. The challenge lies in ascertaining and regulating the effect of N-doping on the pore structure. In this work, lignin was activated using KOH, and then followed by urea N-doping through pyrolysis or hydrothermal methods. At small dosages of KOH (the mass ratio of KOH/lignin = 0.25), in addition to introducing nitrogen-containing functional groups, urea modification boosted pore volume of <1 nm favorable for CO2 adsorption through etching carbon skeleton, while the small dosage of KOH reduced its inherent corrosive hazards. Correlation analysis showed that the dominant influencing factor for CO2 adsorption at ambient temperature and pressure was the pore volume with pore size of 0.6–0.8 nm, whereas nitrogen content (especially N-5 content) was the main influencing factor at high temperatures (50 °C) and low pressures (0.15 bar). The peak enhancement of the C–N bond under the CO2 adsorption at 50 °C by in situ diffuse reflectance infrared Fourier transform test indicated that the nitrogen-containing functional groups have a chemisorption effect on CO2. The adsorbent PK-0.25-HU exhibited adsorption capacity of 4.46 mmol/g (25 °C, 1 bar), 2.97 mmol/g (50 °C, 1 bar). Dynamic separation coefficient of CO2/N2 reached 93.82 in a gas mixture of CO2/N2 = 15 %/85 %.

Co-pyrolysis of Baltic wheat straw and low-density polyethylene bags and its kinetic and thermodynamic behaviour

Wheat cultivation represents about 42 % of the total cereal cultivation area in the Baltic Sea region, generating huge amounts of wheat straw (WS) that needs to be optimally managed. In this context, this research aims to investigate the extent of using pyrolysis process in WS valorization. The experiments were performed using a thermogravimetric (TG) analyzer on WS and its mixtures with low-density polyethylene (LDPE) bags at different mixing ratios (1:1, 1:2, 1:3, 1:4). The released TG vapours were monitored using TG-Fourier transform infrared spectroscopy (TG-FTIR) and chromatography-mass spectrometry (GC-MS). The thermochemical activation energy (Ea) were studied by Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa, Friedman, and Vyazovkin models. The pyrolysis results showed that WS and LDPE could be completely decomposed as a single reaction up to 600 °C and 520 °C, respectively. Aromatic-carbonyl and CO2 were the main FTIR functional group for WS vapour versus -CH2- for LEDP vapour. The GC/MS analysis of WS showed various compounds such as sec-Butylamine (11.88 %), acetic acid (10.68 %), etc., while LDPE showed many compounds without specific trend even when the heating rate was changed. While the co-pyrolysis results showed that WS/LDPE could be decomposed individually in two successive reactions at 335 °C (WS) and 495 °C (LDPE). These results were confirmed by FTIR and GC/MS which showed that the functional groups and chemical compounds of vapour generated at these decomposition zones have similar characteristics to those obtained from pyrolysis of WS and LDPE. Finally, kinetic analysis showed that WS-Baltic (227–250 kJ/mol) is more complex compared to WS-Asian (163–217 kJ/mol) due to its higher ash content. While Ea of WS/LDPE was increases upto 274–291 kJ/mol (1:1), 266–297 kJ/mol (2:1), 268–289 kJ/mol (3:1), and 278–299 kJ/mol (1:4). Also, the enthalpy, and Gibbs free energy coefficients of WS were increased by mixing (1:1) up to 272 J/mol K, while its entropy does not change much by mixing (367 J/mol K). Accordingly, the co-pyrolysis process is a key technology in valorization of WS and convert into value-added chemicals and a sustainable energy source.

Adsorption of cobalt isotope from liquid radioactive waste by carbon nanostructured materials of thermochemical activation of sludge-lignin

One of the urgent problems of modern industry is the accumulation of waste. Waste from the nuclear industry is liquid radioactive waste, pulp and paper industry is sludgelignin. To solve the problem of waste accumulation in these industries, a method of selective purification of liquid radioactive waste by waste products of the pulp and paper industry is proposed. Pyrolysis is an effective way of processing sludge-lignin, as a result of the activation of the pyrolysis product by alkaline reagents, activated carbons were obtained in laboratory conditions, which presumably can selectively extract isotopes of radionuclides from liquid radioactive waste. In the conducted study, the ability of carbon nanostructured materials of thermochemical activation of sludge-lignin to extract the isotope Со27 59 in the form of an ammonia complex was studied. The influence of the pyrolysis conditions: temperature (T), time (T) and dosage of the activator (D) on the response functions: monolayer capacity, heat of adsorption, the value of the maximum adsorption and the characteristic adsorption energy, which can be used to judge the porous structure of activated carbon. The method of the planned experiment is applied — rotatable central composite plan. For clarity, response surfaces are constructed based on experimental data. The analysis made it possible to develop practical recommendations for conducting the pyrolysis process in order to obtain a marketable product — activated carbons from sludge–lignin.

Onion husk-derived high surface area graphene-like carbon for supercapacitor electrode material application

In this study, we report the synthesis of graphene-like carbon derived from onion husk, with potential application as an electrode material in energy storage devices. Graphene-like carbon (GLC) was synthesized from onion husk (OH) by preliminary carbonization at 550 °C, followed by thermochemical activation at various temperatures to determine the optimal activation parameters. The surface morphology of graphene-like carbon from onion husk (GLC-OH) samples after carbonization shows distinct thermal exfoliation of the material. This layering upon activation in KOH promotes the formation of highly porous graphene-like carbon flakes. According to the Brunauer-Emmett-Teller (BET) method, the specific surface area at 850 °C was 1924 m2/g. The X-ray diffraction (XRD) and Raman spectroscopy results reveal the emergence of few-layer graphene with a significant amount of structural defects at 850 °C. As the temperature increases, the formation shifts towards multilayer graphene, which leads to a decrease in the specific surface area of the carbon material. The electrochemical characterization of the assembled GLC–OH–based supercapacitor synthesized at 850 °C revealed a markedly higher specific capacitance value of 131 F/g, along with a Coulombic efficiency of 98 % at a gravimetric current density of 1 A/g. Additionally, it exhibited a low charge transfer resistance (RCT) of approximately 1.4 Ω.Our study investigates the influence of structural changes on the electrochemical performance of biomass-derived activated carbon, highlighting the potential of graphene-like carbon from onion husk as a promising and low-cost material for future energy storage devices.

Thermochemical Activation of Wood with NaOH, KOH and H3PO4 for the Synthesis of Nitrogen-Doped Nanoporous Carbon for Oxygen Reduction Reaction.

Carbonization of biomass residues followed by activation has great potential to become a safe process for the production of various carbon materials for various applications. Demand for commercial use of biomass-based carbon materials is growing rapidly in advanced technologies, including in the energy sector, as catalysts, batteries and capacitor electrodes. In this study, carbon materials were synthesized from hardwood using two carbonization methods, followed by activation with H3PO4, KOH and NaOH and doping with nitrogen. Their chemical composition, porous structure, thermal stability and structural order of samples were studied. It was shown that, despite the differences, the synthesized carbon materials are active catalysts for oxygen reduction reactions. Among the investigated carbon materials, NaOH-activated samples exhibited the lowest Tafel slope values, of -90.6 and -88.0 mV dec-1, which are very close to the values of commercial Pt/C at -86.6 mV dec-1.

Enhancing lithium-sulfur battery performance with biomass-derived graphene-like porous carbon and NiO nanoparticles composites

Despite the promising specific discharge capacity and energy density, lithium-sulfur batteries (LSBs) encounter challenges related to the lithium polysulfides (LiPSs) shuttle effect and volume expansion during extended cycling. A pivotal aspect of this research lies in the strategic synthesis of a hybrid of non-polar and polar compounds, creating an effective host and separator modifier tailored for LSBs for improvement of their electrochemical characteristics. Precisely, high-specific surface area graphene-like porous carbon (GPC) was successfully synthesized from inexpensive and abundant rice husk (RH) waste via step-by-step carbonization and thermo-chemical activation, and subsequently used as a porous matrix for sulfur cathode preparation using the melt-diffusion technique. Furthermore, composites based on GPC decorated with NiO nanoparticles were synthesized with varying GPC to Ni(NO3)2 ratios and utilized as an efficient separator modifier. The obtained results revealed that the cell consisting of GPC@S cathode and GPC-NiO-20 modified separator exhibited accelerated LiPSs redox reactions and suppressed the shuttle effect. In particular, the GPC@S/GPC-NiO-20 cell demonstrated excellent initial discharge capacity (1519 mAh g−1 at 0.2 C), promising long-term cycling performance (capacity decay of 0.091 % per cycle over 400 cycles at 1 C), and remarkable rate performance (568 mAh g−1 at 2 C).

Adjustment of textural and acidic properties of aluminum oxide by modifying the product of thermo-chemical activation of gibbsite with acids in hydrothermal conditions

The paper considers the effect of the modifier (nitric and sulfuric acids) on the physicochemical properties of aluminum oxide as a component (carrier) of cracking catalysts. The modifier was introduced during pre-treatment of the thermochemical activation product of gibbsite (TCA product). The article describes the influence of the amount of acids introduced during the TCA product pre-treatment stages (hydration and hydrothermal treatment (HTT)) on the acidic and textural properties of the resulting product. The activity of the obtained aluminum oxide samples during catalytic cracking of n-hexadecane, a model feedstock, was evaluated. All obtained samples were compared with aluminum oxide produced by the sulfate redeposition method. The cracking of hydrotreated vacuum gasoil on catalytic systems “aluminum oxide – zeolite Y″ was investigated.

Thermochemical activation of raw chickpea (Cicer arietinum) stalk biomass for enhanced valorization

Thermochemical activation of raw chickpea (Cicer arietinum) stalk biomass for enhanced valorization

Sweetwood Lignin As a Promising Precursor Towards Multi-Functional Electrode Material

Currently, industrial development has led to a constant increase in demand for energy and sustainable energy resources, so there is an intensive search for a replacement for fossil fuels. The goal of this research is synthesis multi-functional electrode material using "Sweetwood" lignin (industrial by-product from sugars solutions for fuels, chemicals etc.) as a raw material via thermochemical activation with subsequent N-doping. Three-dimensional hierarchical micro- and mesoporous structures of activated carbon materials show promising results as an alternative PGM-free oxygen reduction catalysts for alkaline systems. The ORR activity of the synthesized carbon catalysts may be associated with the high percentage of pyridinic nitrogen, highly developed surface area, micro- and mesoporous ratio and balance, and lack of stacking defects of graphene layers. Furthermore, "Sweetwood" lignin carbon materials were assessed as electrode in supercapacitors. It was found that activation temperature plays a significant role on the specific capacitance which is additionally improved by doping of the carbon precursor with nitrogen. Acknowledgment The “Sustainably Produced Carbon Nanomaterials for Energy Applications (SuNaMa)” benefits from a 988000 € grant from Iceland, Liechtenstein, and Norway through the EEA Grants. The aim of the project is to develop innovative, high-performance, highly conductive, electrocatalytically active, durable, cost-effective, and high surface area nanocarbon materials. Project contract with the Research Council of Lithuania (LMTLT) No. is S-BMT-21-12 (LT08-2-LMT-K-01-055).

Ni supported on bioapatite for WGS: Improving catalyst stability and H2 selectivity by Pt-doping and thermochemical activation of the support

Catalytic properties of Ni and NiPt catalysts supported onto naturally derived hydroxyapatite (HAp) were investigated for the Water-Gas Shift (WGS) reaction in the 200–450 °C range. HAp was obtained by thermochemical conversion of waste animal bones which yield a porous solid mainly composed by apatite. A feed composition representative of real reformer outlet stream was used (CO/H2O/CO2/H2 = 5/46/4/31 mol %) at a gas hourly space velocity of 120,000 h−1. The catalysts were thoroughly characterised by N2 physisorption, ICP-AES, H2-chemisorption, XPS, FTIR, SEM-EDX, XRD, H2-TPR, CO2-TPD, and NH3-TPD. From the light-off catalytic tests, it was found that all catalysts reached the equilibrium CO conversion in the 350–400 °C range. Pt doping into pristine Ni/HAp did not enhance neither catalytic activity nor selectivity to hydrogen. Interestingly, thermochemical activation (acid treatment) aimed to reduce the CH4 formation (@ 350 °C) by around two-fold (25 % vs. 9–14 %) with a concomitant increase in the hydrogen yield. Moreover, catalytic stability was also improved. For instance, after 30 h TOS CO conversion dropped by 50 % for the pristine Ni/HAp and only 7 % for NiPt/SHAp catalyst. Similarly, the latter showed the highest and most stable hydrogen yield throughout all the long-term test.

Wastewater Treatment by Improving the Local Clay Capacity with Chemical and Thermal Activation

Worldwide, liquid effluents are generally discharged into the environment untreated, which, in turn, are affecting humans, animals and plants. Preserving our environment is a priority, especially with the emergence of epidemics in recent years. As a part of our investigation, we aim to treat the wastewater of the Ouargla region by enhancing the adsorption capacity of local clay collected from El-Oued (Elmghaier, south of Algeria) using thermo-chemical activation for the removal of organic pollutants. The clay used was (illite, kaolinite, and quartz 62.0%, 27.0% and 11.1%, respectively). The experiments proved the efficiency of enhancing the adsorption capacity of local clay by thermo-chemical activation in the treatment of urban wastewater to determine the efficiency by the following characteristics: chemical oxygen demand, biochemical oxygen demand, total suspended solids, and turbidity, respectively. Acid-activated clay with sulphuric acid achieved high efficiency on polluted water purification at the ideal concentration (0.75 N) and an adsorption rate of (80.16%, 90.74%, 93.33% and 90.74%), while the result decreased in the optimal concentration of acid activated clay HCl (0.134 N) and the adsorption rate was 73%, 60.92%, 94.31% and 65.57%. The thermal activation effect of the clay studied under optimal temperature conditions (400°C) shows that the adsorption ratio increased with higher temperatures (82%, 65%, 89.56% and 78.65%).

Hydroxyl-rich porous carbons from sulfated sucrose for supercapacitors

Using sucrose as a precursor, hydroxyl-rich porous carbons are synthesized by concentrated sulfuric acid pre‑carbonization and further thermochemical activation. The activating agents have significant effects on the physicochemical and electrochemical properties of the resultant porous carbons. Compared with NaOH and K2CO3, KOH delivers the strongest pore etching ability, resulting in a specific surface area of the microporous-dominated carbon (C-PH) as high as 2097 m2 g−1 with a pore volume of 1.62 m3 g−1. In a three-electrode system in a basic aqueous electrolyte, when the mass loading of C-PH is 3 and 5 mg, the specific capacitance of 313 and 295 F g−1 is harvested at 1 A g−1, respectively. In a symmetrical-electrode system, when the mass loading is 3, 5, and 7 mg, the simulated device enclosed C-PH achieves the specific capacitance of 281, 265, and 249 F g−1 at 1 A g−1, respectively. In the case of the corresponding loading mass, the device achieves the energy density of 9.7, 9.3, and 8.6 Wh kg−1 at the power density of 253, 240, and 224 W kg−1, respectively. Results demonstrate KOH has the strongest thermochemical pore-making ability and the resultant hydroxyl-rich porous carbon delivers promising potential in constructing high-performance carbon-based supercapacitors.