Chemical Activation Route Research Articles

Fe-doped biomass-derived activated carbons as sustainable electrode materials in supercapacitors using different electrolytes

In the search of sustainable and low-cost materials, able to reinforce circular economy, different activated carbons were obtained from agroindustry wastes, by means of a chemical activation route, after the doping of their corresponding biochars with Fe-based species through an incipient wetness method. These activated carbons were assessed as active electrode materials in supercapacitors using various electrolytic media, including aqueous, organic and ionic liquid electrolytes. The electrochemical results obtained revealed an excellent performance for all porous materials and electrolytes under evaluation, reaching the highest specific capacitance of 334F/g at a current density of 0.02 A/g using an aqueous electrolyte. The highest specific capacitance using an organic electrolyte and an ionic liquid electrolyte were 214F/g and 166F/g, respectively. It was found that activated carbons with a relevant mesopores volume, and pore sizes around 1 nm, achieved a better specific capacitance when using aqueous and organic electrolytes. However, heteroatoms as oxygen and iron enhanced the electrochemical performance of the device using the ionic liquid as electrolyte, thus achieving the highest energy and power density values (up to 63 Wh/kg and 1606 W/kg, respectively) among the different systems evaluated.

High surface area peat moss biochar and its potential for Chromium metal adsorption from aqueous solutions

Activated carbons (ACs) have been synthesized using local peat moss biomass for adsorption of heavy metal ions. Adsorbents with different surface areas and pore sizes were obtained using a chemical activation route with different impregnation ratios (20%, 30%, and 40%) of phosphoric acid. The carbonization process was carried out in a tubular furnace under flow of nitrogen (N2) at 500 °C, and 600 °C. Physicochemical properties of developed activated carbon have been evaluated by several techniques such as; X-ray diffraction, Scanning Electron Microscopic, Energy Dispersive X-ray Spectroscopy, Nitrogen adsorption isotherm, Pore size distribution analysis, and Fourier-transform analysis. Moreover, adsorption of chromium ions (Cr+2) from an aqueous solution under different variables was carried out. Heavy metal concentration (20 - 200) ppm, the dosage of adsorbent (0.1 – 0.5) g/L, the time of contact (0 - 220) min, and initial pH (2 - 8) were studied. Results showed that a synthesis route by chemical activation with 30% H3PO4 concentration at 600 °C for 3 h gave the highest BET surface area and pore volume (1692.6 m2/g and 1.55 cm3/g) respectively, compared with other prepared samples. As well as, the removal results show that the maximum adsorption capacity was 493.3 mg/g at 200 mg/L of initial heavy metal concentration, 6.5 pH, 0.3 g/L activated carbon dosage, and 180 min contact time. The Freundlich isotherm was the better description of the adsorption equilibrium data, while the pseudo-second-order model shows the most accurately describes of adsorption kinetics, which indicates that chemisorption is dominant in the adsorption process. Temperature and thermodynamics parameters were studied. The positive value of enthalpy indicates that the adsorption was endothermic.

Effect of Porosity and Surface Chemistry on CO2 and CH4 Adsorption in S-Doped and S-/O-co-Doped Porous Carbons

The aim of this study was to determine the adsorption performance of a petroleum pitch-based activated carbon (PPAC1:3) before and after a post-treatment with H2S. In the first step, a microporous activated carbon (PPAC1:3) with a highly developed porous structure was produced through a chemical activation route with KOH. Afterward, the synthesized activated carbon was thermally treated yielding two different series of functionalized activated carbons: (i) a series of carbons were treated directly with H2S at elevated temperatures (600 °C and 800 °C), and (ii) a series of carbons were generated by combining an oxidation treatment with plasma followed by H2S treatment at elevated temperatures (600 °C and 800 °C). The chemical and structural characteristics of the S-doped and S-/O-co-doped porous carbons were investigated by means of different experimental techniques, such as XRD, RAMAN, FESEM, XPS, TPD, N2, and CO2 adsorption, and finally tested in CO2 and CH4 adsorption at atmospheric and high pressure. The functionalized porous carbons possessed specific surface areas of 2420–2690 m2/g, total pore volume of 1.05–1.18 cm3/g, and sulfur content up to 2.55 atom % (the sulfur content of the original carbon was 0.19%). After a careful analysis of the carbon dioxide and methane uptake at atmospheric (0.1 MPa) and high pressure (4 MPa), adsorption results confirm that the microporous structure is the main structural parameter defining the adsorption performance and, to a lower extent, the surface chemistry. Overall, a significant improvement in the total uptake can be appreciated after the H2S treatment.

Sorbent extraction behavior of cesium and strontium from nitric acid solutions using a new high thermal stability material

In this study a new low-cost carbonaceous material was prepared from husks of opuntia-ficus-indica as a starting material (precursor) which was accomplished by chemical activation route using H3PO4 impregnation. The material has been identified by different analytical tools. The sorption performance of Cs(I) and Sr(II) from HNO3 solutions was examined through batch system. Variations of the distribution coefficients (Kd) as a function of HNO3 concentration in the range 0.001–5.0 M were presented. Some of separation probabilities were suggested. The results attained signals that the Sr(II) selectivity is higher than that of Cs(I) at high molarities. The retention capacity (qe) of Cs(I) and Sr(II) ions increased with growing temperature. The capacities at 0.001 M HNO3 are 34 and 108 mg/g for Cs(I) and Sr(II), respectively. Whereas, at 2.0 M HNO3 capacities were about 4 and 37 mg/g for each of Cs(I) and Sr (II), respectively. This studies demonstrates that the prepared carbonaceous sorbent is an economically effective sorbent for retention of Cs(I) and Sr(II) species from HNO3 solutions. Cs(I) and Sr(II) removal potential was tested from simulated low- and intermediate-level radioactive waste samples.

Methylene Blue Removal by Activated Carbon from Platanus Orientalis Leaves

In this study, activated carbon was produced from platanus orientalis leaves and the adsorption of methylene blue onto activated carbon was investigated. Facile chemical activation route was conducted for activation process of lignocellulosic leaves. ZnCl2 was used as activating agent with different ratios. Morphological, structural and adsorption characteristics of samples were determined by using optical microscopy, Fourier transform infrared spectroscopy, Braunauer-Emmet-Teller spectroscopy and UV-vis spectroscopy. Surface characterization showed that activation with ZnCl2 resulted high surface area (~1024 m2 g-1) and total pore volume (~0.431 cm3 g-1) compared with crude carbonized leaves samples.

Watermelon Peel‐Derived Heteroatom‐Doped Hierarchical Porous Carbon as a High‐Performance Electrode Material for Supercapacitors

AbstractThis work presents for the first time the systematic characterization and excellent supercapacitor performance of heteroatom‐doped porous carbon materials (HPC) synthesized by direct pyrolysis of watermelon peel and urea via molten salt template route in air with non‐toxic activating agent. The molten salt not only protects the derived carbon from burning during high‐temperature pyrolysis, but can also be etched to generate abundant hierarchical pores in the final products. The obtained HPC exhibits a high specific surface area of 1660 m2 g−1 and shows high specific capacitances of up to 278 F g−1 in 1 M H2SO4 electrolyte. The symmetrical device also demonstrates a remarkable specific capacitance of up to 226 F g−1 and ultrahigh initial capacitance retention of 98 % after 10,000 cycles of charge/discharge at the current density of 10 A g−1. The porous carbon produced via this green chemical activation route demonstrates great potential as electrode materials in supercapacitor.

Synthesis, Characterization, Adsorption Isotherm, and Kinetic Study of Oil Palm Trunk-Derived Activated Carbon for Tannin Removal from Aqueous Solution.

Oil palm trunk (OPT) represents one of the five main oil palm biomass wastes with high carbon content that can be economically converted to a large surface area, porous activated carbon (AC) adsorbent to treat palm oil mill effluent wastewater in Indonesia and Malaysia. In the first portion of this work, the design of the experiment was used to determine the optimum set of synthesis parameters required to maximize the iodine number of AC [i.e., Brunauer–Emmett–Teller (BET) specific surface area indicator] prepared from OPT via chemical activation route using H3PO4. The iodine numbers of AC and AC yield were probed as the impregnation ratio, the activation time, and the activation temperature were varied in the range of 0.28–3.47, 5.68–69.32 min, and 379–521 °C, respectively. An impregnation ratio of 2.29, an activation time of 6 min, and an activation temperature of 450 °C were identified as the optimum set of synthesis parameters. In the second portion of the work, the AC synthesized using the optimum parameters were then characterized and tested as an adsorbent for tannin. N2 sorption results revealed that the AC exhibits type IV isotherm, that is, contains micropores and mesopores and displays a relatively high BET specific surface area of 1657 m2 g–1. Adsorption equilibria isotherms for tannin adsorption onto the AC were collected at three different pH of 2, 4, and 6 and were nonlinearly fitted using Langmuir and Freundlich isotherm models, where the Langmuir isotherm gave better fitting than Freundlich. The higher adsorption capacity at lower pH can be explained in terms of the absence of electrostatic repulsion interaction between the AC surface and the tannic acid species as suggested by the point of zero charges (pHpzc) of 4.8 and an increasing ionization of tannic acid with pH rise between 4 and 7. Adsorption kinetics data were also obtained at four different pH of 2, 4, 6, and 8 where the nonlinear pseudo-first-order model best fitted the kinetic at pH of 2 and the nonlinear pseudo-second-order model represented the kinetic best at the remaining higher pH, which suggests that tannin adsorption onto AC occurred by physisorption at pH of 2 and by chemisorption at pH of 4, 6, and 8.

Boosting gravimetric and volumetric energy density of supercapacitors by 3D pomegranate-like porous carbon structure design

Recently, the heteroatom-enriched porous carbons have received considerable attention on the research of electrodes with high gravimetric capacitances for supercapacitors (SCs). However, their relatively low volumetric capacitances have limited their practical applications due to very low packing density and poor ion diffusion at high mass loadings. In this study, by means of a facile modified chemical activation route, a functionalized N and O co-doped three-dimensional (3D) hierarchical pomegranate-like porous carbon (PPC) was rationally synthesized. First, A core–shell structured precursor composite for PPC was constructed. The polypyrrole (PPy) with the desired functional group was adopted as the precursor of the pomegranate-like core, and the polyacrylamide (PAM) hydrogel as the precursor of the pomegranate-like shell (designated as PPy/PAM). Then, after calcination of the PPy/PAM hydrogel precursor composites, a novel 3D hierarchical PPC was achieved. The as-obtained PPC offers short diffusion paths of ions, increases packing density and provides abundant active sites for pseudocapacitance by increasing self-oxygen–nitrogen-doped content. The performance tests of SC with PPC manifest that at 156 W kg−1 (109.7 W L-1), boosted energy density of 11.5 Wh kg−1 (8.05 Wh L-1) can be achieved. The as-obtained PPC is the promising electrode material of high-performance SCs for practical applications.

Mussel-Inspired Polymerization of Peptides: The Chemical Activation Route as Key to Broaden the Sequential Space of Artificial Mussel-Glue Proteins.

A previously introduced tyrosinase-activated polymerization of Tyr- and Cys-bearing peptides yielding artificial mussel-glue proteins is realized without the need of the specific enzyme by a chemical activation route. This decouples the sequence of polymerizable peptides (unimers) from the constraints of tyrosinase substrates and enables the polymerization of minimal motifs such as Dopa-Lys-Cys (Umini *KC ) or Dopa-Gly-Cys (Umini *GC ). In the polymerization procedure, sodium periodate is used to oxidize Dopa residues of the unimers to Dopa-quinones to which the thiol of a Cys residue is added in a Michael-type reaction. The resulting polyUmini *KC and polyUmini *GC exhibit a thiol-catechol connectivity as a potent adhesive functionality at each repeat unit. QCM-D experiments show the excellent substrate adsorption properties of the products from the chemically activated polymerization. On aluminum oxide surfaces, polyUmini *KC rapidly forms a coating, even under seawater model conditions and the coating resists rinsing with hypersaline solution of 4.2 M salt mixtures. While the sodium periodate oxidation is less specific than the tyrosinase reaction and requires the implementation of Dopa instead of Tyr residues into the polymerizable unimers, the chemical route makes scale-up more easily accessible.

Activated carbon derived from coconut coir pith as high performance supercapacitor electrode material

Abstract In this study, activated carbons were synthesized from coconut coir pith, an inexpensive and abundant type of biomass in Thailand. The coconut coir pith was activated by a combined physical and chemical activation route, using NaOH-to-char ratios of 1:1, 2:1 and 3:1 by weight. A high surface area of 2056 m2 g−1 was achieved with NaOH-to-char weight ratio of 3:1. Using this activated carbon in a symmetrical cell with aqueous electrolyte, high capacitance values were achieved. The specific capacitance values obtained were 232.3 F g−1 at 0.1 A g−1 and 192.0 F g−1 at 1 A g−1. Long-term cycling tests at 0.5 A g−1 showed 95.4% capacitance retention after 5000 cycles. The high specific capacitance was attributed to the high micropore volume. The superior rate capability was from the interconnected pore structure of the activated carbon which allowed for efficient ion transport.

Sustainable porous activated carbon from Polyalthia longifolia seeds as electrode material for supercapacitor application

Polyalthia longifolia Seeds (PLS) derived activated carbon (AC) samples were prepared at different temperatures (600, 700, 800 and 900 °C) by the pyrolytic chemical activation route. The as-prepared PLS-ACs were characterized by spectral and analytical tools. The electrochemical characterization studies were performed by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and Impedance spectroscopic techniques. A three-electrode system, consisting of the as-prepared PLS-AC samples coated nickel foil (working electrode), Ag/AgCl (reference electrode) and Pt-wire (counter electrode) in 1 M sodium sulfate (Na2SO4) was constructed. The pronounced specific capacitance (Csp) value of 365 Fg−1 was achieved at current density of 1 Ag−1 with reference to PLS-AC sample pyrolyzed at 900 °C with 92% retention even after 5000 charge/discharge cycles, substantiating the significant recycling durability. Furthermore, the prominent electrochemical behaviour under the selected potential window was supportive of its capacitive nature. The low-cost high performance carbon materials, prepared from the bio-waste, exhibited enhanced Supercapacitance, suitable for power storage devices. Moreover, the fabricated symmetric device using PLS-9 showed the high energy density of 27.5 Wh kg−1 at the power density of 499 W kg−1. Thus, the highly porous PLS-9 electrode was noted to a promising candidate for high-performance supercapacitors.

Experimental evaluation of activated carbon derived from South Africa discard coal for natural gas storage

Lacking in literature is the use of discard coal to produce activated carbon and in its subsequent use in the storage of natural gas. In this study, the characterization and gas storage evaluation of a largely porous activated carbon with large surface area synthesized from discard coal were investigated. Discard coals are waste material generated from coal beneficiation process. In developing the activated carbon, chemical activation route with the use of KOH reagent was applied. The effects of KOH/discard coal weight ratio (1:1, 2.5:1, 4:1), temperature (400–800 °C) and particle size (0.15–0.25 mm, 0.25–0.5 mm, 0.5–1 mm) on the adsorptive properties of the activated carbon were methodically evaluated and optimized using response surface methodology. The synthesized activated carbon was characterized using BET, SEM/EDS, and XRD. The results showed that for each activation process, the surface area and pore volume of the resulting activated carbon increased with increased temperature and KOH/discard coal weight ratio. The maximum surface area of 1826.41 m2/g, pore volume of 1.252 cm3/g and pore size of 2.77 nm were obtained at carbonization temperature of 800 °C and KOH/discard coal weight ratio of 4:1. Methane and nitrogen adsorption data at high pressure were fitted to Toth isotherm model with a predictive accuracy of about 99%. Adsorption parameters using the Toth model provides useful information in the design of adsorbed natural gas storage system. According to the requirements of adsorbent desired for natural gas storage, it could be stated that the synthesized activated carbon could well be applied for natural gas storage.

Immense Microporous Carbon@Hydroquinone Metamorphosed from Nonporous Carbon As a Supercapacitor with Remarkable Energy Density and Cyclic Stability

We report transformation of a cost-effective nonporous carbon (NC) to an immense microporous carbon (IMC) employing a simple chemical activation route at 750 °C. N2 adsorption/desorption experiments revealed a remarkable increase in BET surface area (80–3030 m2 g–1) for successor nanomaterial (IMC) in comparison to precursor nanomaterial (NC) presumably due to enhanced accessibility of reaction surface area on carbon material for oxidants to react. In consequence, 250 times specific capacitance enhancement (2.5–605 F g–1 at 0.5 A g–1 current density) was observed in 2 M H2SO4 using a three-electrode configuration. Further, a massive specific capacitance of 1177 F g–1 with a remarkable energy density of 163 Wh kg–1 has been achieved by addition of hydroquinone in electrolyte with IMC (IMC@H2Q) employing a two-electrode configuration. Notably, a simple electrode potential dependent chemical reversibility for hydroquinone redox chemistry in the long term cyclic experiment (95% capacitance retention after 500...

Chemical and structural optimization of ZnCl2 activated carbons via high temperature CO2 treatment for EDLC applications

Development of biomass based activated carbon materials for electrical double layer capacitor (EDLC) usage has gained attention as a result of requesting efficient and low cost energy storage device production. In this study, pine cone based activated carbons were produced with a combined chemical and physical activation route. ZnCl2 and CO2 were used for chemical and physical activation of the material, respectively. Activation parameters are adjusted to give different chemical and textural characteristics. FTIR and Raman spectroscopies were used for functional group identification and structural order characterization, respectively. As a result, efficient active materials for EDLC usage were obtained, with as high as 87 F/g specific capacitance in organic electrolytes.

Synthesis of garlic skin-derived 3D hierarchical porous carbon for high-performance supercapacitors.

A three-dimensional hierarchical porous carbon is synthesized via a facile chemical activation route with garlic skin as the precursor and KOH as the activating agent. The as-obtained carbon presents a high specific surface area of 2818 m2 g-1 and a hierarchical porous architecture containing macroporous frameworks, mesopores (2-4 nm), and micropores (0.6-1.0 nm). As the electrode material for a supercapacitor, due to its unique interconnected porous structure, this garlic skin-derived carbon exhibits excellent electrochemical performance and cycling stability. At a current density of 0.5 A g-1, the capacitance is up to 427 F g-1 (162 F cm-3). Even at a high current density of 50 A g-1, the capacitance can be maintained to a high value of 315 F g-1 (120 F cm-3). After charging-discharging at a current density of 4.5 A g-1 for 5000 cycles, the capacitance retention is as high as 94%. The results suggest that this garlic skin-derived 3D hierarchical porous carbon is a promising electrode material for high-performance supercapacitors.

Nitrogen and phosphorus co-doped carbon hollow spheres derived from polypyrrole for high-performance supercapacitor electrodes

Nitrogen and phosphorus co-doped carbon hollow spheres (NPCHSs) have been prepared by a carbonization and subsequent chemical activation route using dehydrated polypyrrole hollow spheres as the precursor and KOH as the activating agent. NPCHSs are interconnected into a unique 3D porous network, which endows the as-prepared carbon to exhibit a large specific surface area of 1155 m2 g−1 and a high specific capacitance of 232 F g−1 at a current density of 1 A g−1. The as-obtained NPCHSs present a high-level heteroatom doping with N, O and P contents of 11.4, 6.7 and 3.5 wt%, respectively. The capacitance of NPCHSs has been retained at 89.1% after 5000 charge–discharge cycles at a relatively high current density of 5 A g−1. Such excellent performance suggests that NPCHSs are attractive electrode candidates for electrical double layer capacitors.

High energy supercapacitors based on interconnected porous carbon nanosheets with ionic liquid electrolyte

Future development of electrochemical energy storage systems requires low-cost supercapacitors with not only an outstanding power performance but also the high energy. Herein, interconnected porous carbon nanosheets are prepared via a simple hydrothermal process combined with chemical activation route by using reed as the precursor and KOH as the activating agent. The as-prepared carbon nanosheets exhibits a high specific surface area (up to 2183 m2 g−1), and a hierarchical porous structure containing combined macroporous scaffolds and meso/microporous textures. When tested as electrode materials for ionic liquid-based supercapacitors, the carbon nanosheet exhibits a high capacitance of 147 F g−1 and a good capacitance retention ratio of 48.3% at 100 A g−1, with a high cycling life stability (10% loss after 10000 cycles). Moreover, the assembled supercapacitor yields a maximum energy and power density of 11.4 Wh kg−1 and 98 kW kg−1 based on the all components of the packaged device. The remarkable characteristics of the produced carbon materials indicate that the novel precursor-synthesis route offers promising potential for low-cost production for supercapacitors.

A Chemical Route to Activation of Open Metal Sites in the Copper-Based Metal-Organic Framework Materials HKUST-1 and Cu-MOF-2.

Open coordination sites (OCSs) in metal-organic frameworks (MOFs) often function as key factors in the potential applications of MOFs, such as gas separation, gas sorption, and catalysis. For these applications, the activation process to remove the solvent molecules coordinated at the OCSs is an essential step that must be performed prior to use of the MOFs. To date, the thermal method performed by applying heat and vacuum has been the only method for such activation. In this report, we demonstrate that methylene chloride (MC) itself can perform the activation role: this process can serve as an alternative "chemical route" for the activation that does not require applying heat. To the best of our knowledge, no previous study has demonstrated this function of MC, although MC has been popularly used in the pretreatment step prior to the thermal activation process. On the basis of a Raman study, we propose a plausible mechanism for the chemical activation, in which the function of MC is possibly due to its coordination with the Cu(2+) center and subsequent spontaneous decoordination. Using HKUST-1 film, we further demonstrate that this chemical activation route is highly suitable for activating large-area MOF films.

Bi-functional porous carbon spheres derived from pectin as electrode material for supercapacitors and support material for Pt nanowires towards electrocatalytic methanol and ethanol oxidation

Porous carbon spheres (PCSs) are prepared via a facile hydrothermal carbonization and chemical activation route with pectin as the biomass precursor. The as-obtained PCSs present a large specific surface area (2440m2g−1), well-balanced micro/mesoporosity with narrow pore size distribution and high content of oxygen-containing functional groups. The structure features make the PCSs an ideal electrode material for electrochemical energy storage. As electrode material for supercapacitors, the PCSs exhibit a high specific capacitance, good rate capacity and cycling stability. Furthermore, the PCSs show attractive property as support material for Pt electrocatalysts. Pt nanowires (PtNWs) grown on the PCSs interconnect with each other to form a porous nanowires network structure. The three-dimensional (3D) hybrid catalyst material consisting of PtNWs network supported on PCSs exhibit superior catalytic activity and stability towards both methanol and ethanol electro-oxidation in acidic media. In addition, owing to the rich presence of surface oxygen groups on PCSs, the CO-poisoning tolerance of the supported Pt nanowires is greatly promoted.

Synthesis of sulfonated porous carbon nanospheres solid acid by a facile chemical activation route

Generally, porous carbon nanospheres materials are usually prepared via a template method, which is a multi-steps and high-cost strategy. Here, we reported a porous carbon nanosphere solid acid with high surface area and superior porosity, as well as uniform nanospheical morphology, which prepared by a facile chemical activation with ZnCl2 using resorcinol-formaldehyde (RF) resins spheres as precursor. The activation of RF resins spheres by ZnCl2 at 400°C brought high surface area and large volume, and simultaneously retained numerous oxygen-containing and hydrogen-containing groups due to the relatively low processing temperature. The presence of these functional groups is favorable for the modification of –SO3H groups by a followed sulfonation treating with sulphuric acid and organic sulfonic acid. The results of N2 adsorption–desorption and electron microscopy clearly showed the preservation of porous structure and nanospherical morphology. Infrared spectra certified the variation of surface functional groups after activation and the successful modification of –SO3H groups after sulfonation. The acidities of catalysts were estimated by an indirect titration method and the modified amount of –SO3H groups were examined by energy dispersive spectra. The results suggested sulfonated porous carbon nanospheres catalysts possessed high acidities and –SO3H densities, which endowed their significantly catalytic activities for biodiesel production. Furthermore, their excellent stability and recycling property were also demonstrated by five consecutive cycles.