Effect Of Activation Temperature Research Articles

Preparation of pistachio shell-based porous carbon and its adsorption performance for low concentration CO2

In this study, high-performance porous carbon for CO2 adsorption was synthesized from pistachio shells and modified with urea to enrich nitrogen content in the porous structure. The effects of activation temperature, KOH-to-carbon ratio, and urea addition on the pore structure and CO2 adsorption capacity of the porous carbon were investigated. Characterization was conducted using N2 adsorption-desorption isotherms, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FT-IR). Results showed that under preparation conditions of 700 °C, KOH-to-carbon ratio of 2, and 15 wt% urea concentration, the synthesized GAC-15-2-700 porous carbon exhibited a maximum specific surface area of 1395 m2/g, micropore volume of 0.505 cm3/g, and N-5 peak area ratio of 65.57%. It achieved a CO2 adsorption capacity of 3.56 mmol/g. Nitrogen functional groups on the porous carbon primarily existed as pyridinic N (N-6), pyrrolic/pyridinic N (N-5), and quaternary N (N-Q), with the enriched micropores and high N-5 content being crucial for CO2 adsorption.

Pyrolytic conversion of Mesua ferrea testa to nitrogen-doped porous carbon for supercapacitor applications

Developing a high energy density supercapacitor is of great challenge due to the low surface area of commercial activated carbon. The present work aims at developing highly porous nitrogen-doped porous carbon from biomass for supercapacitors. Herein, Mesua ferrea (Nahor) shells, a widely available biomass in northeast India, was used to prepare porous carbon. The effect of activation temperature on structural, textural properties, and electrochemical performance is studied. The carbonization temperature highly influenced the pore structure, porosity, surface area, and thereby influencing the electrochemical performance. The porous carbon pyrolyzed at 700 °C delivered a high specific capacitance of 210 F g-1 at 1 A g-1, higher than porous carbon made at higher temperature (27.5 F g-1 at 1 A g-1 for carbon pyrolyzed at 800 °C). The results provide insights that will be of use in the development of high-energy-density capacitors employing biomass-derived porous carbon.

N, P co-doped microporous carbon derived from the central part of corn cob for high-performance symmetrical supercapacitors

A kind of N, P co-doped carbon material containing only micropores was prepared from the central part of corn cob. The effect of activation temperature on product structure and capacitive properties was studied in detail. The characterization results show that the carbon material (NPCC-650) prepared at 650 °C has high content of heteroatoms, large specific surface area and abundant micropores. Due to the structural advantages of NPCC-650, electrochemical tests show that the specific capacitance and rate properties of NPCC-650 are significantly better than the samples prepared at 550 °C and 750 °C. In addition, the symmetric supercapacitor assembled based on NPCC-650 has a specific capacitance of 45.8 F g−1 at a current density of 0.5 A g−1, corresponding to the energy density of 12.5 Wh kg−1. This research not only provides a method for the high value-added utilization of agricultural waste, but also provides an idea for the preparation of cheap and high-performance micropore carbon-based electrodes.

A facile approach to the preparation of S-doped porous carbons for CO2 adsorption

In the current work, we explored the direct synthesis of S-doped porous carbons employing cesium methanesulfonate as a novel bifunctional chemical activator. The obtained carbons showed high surface area (654–2264 m2/g) and high S content (6.56–15.13 wt%). Effects of activation temperature and cesium methanesulfonate amount on the carbons’ properties were also studied. The obtained carbons showed CO2 uptake of 3.58–4.76 mmol/g at 0 °C and 1 bar. Effects of textural properties and S-doping on CO2 adsorption performances were discussed.

Preparation of nitrogen-doped activated carbon from bio-oil residue for efficient CO2 adsorption

An efficient strategy for the resourcezation of waste bio-oil residue was developed to fabricate nitrogen-doped activated carbon (NAC) as CO2 adsorbent. The NAC was produced by in-situ nitrogen-doped carbonization and K2CO3 activation, using urea as nitrogen source. The effects of activation temperature, mass ratios of urea to bio-oil residue (U/O ratio) and K2CO3 to char (K/C ratio) on the physicochemical properties and CO2 adsorption performance of NAC were investigated. Under the conditions of activation temperature of 750 °C, U/O ratio of 1 and K/C ratio of 3, the as-prepared NAC exhibited the greatest CO2 adsorption performance with an excellent CO2 adsorption capacity of 6.22 mmol/g at 1 bar and 0 °C, which was much higher than that without nitrogen doping (2.21 mmol/g). In addition, the CO2/N2 selectivity of NAC was 14.3 and the adsorption capacity loss was below 1% after 5 consecutive cycles, revealing promising potentials in carbon capture applications.

Nitrogen-Doped Activated Biocarbon from the Agroindustrial Residue of Jatropha Oilcake for Symmetric Supercapacitors: a Study on the Effect of Activation Temperature

Nitrogen-Doped Activated Biocarbon from the Agroindustrial Residue of Jatropha Oilcake for Symmetric Supercapacitors: a Study on the Effect of Activation Temperature

Study of activation methods for Ortho-para hydrogen catalysts in a small isothermal converter based on gas chromatography at LN2 temperature

The efficiency of the O–P catalyst activation directly affects how long liquid hydrogen may be kept. The ideal O–P catalyst activation condition must therefore be investigated. In this study, the effects of activation temperature, activation duration, and activation methods on the catalytic efficiency of a commercial O–P catalyst were thoroughly evaluated experimentally. We assessed the O–P catalysts' catalytic performance under richer activation conditions compared with previous studies. We also employed multiple linear regression to analyze the effects of the aforementioned experimental factors based on our experimental data. Results suggest that O–P catalyst for industrial applications should be activated at 160 °C for 8–12 h while being constantly vacuumed. We also found that the activation temperature had the largest influence on the catalytic performance of O–P catalyst. The pertinent experimental findings from this investigation provide a reference for the development and use of Ortho-Para hydrogen converters in hydrogen liquefiers.

Influence of activation temperature and prestress on behavior of Fe-SMA bonded joints

The prestressed strengthening of structures via use of bonded iron-based shape memory alloys (Fe-SMAs) has proven promising, albeit with concerns regarding the temperature dependency of the adhesive properties. In this study, the effect of activation temperature and generated prestress are investigated experimentally. Six Fe-SMA-to-steel adhesively bonded joints, comprising different Fe-SMA strips (non-prestrained and prestrained) and activation strategies (full activation and partial activation), were prepared, activated via electrical resistance heating, and tested under quasi-static loading. It is found that the bond–slip behavior of a joint with activation can be modeled by that of an equivalent non-activated joint. The generated prestress influences the full-range behavior by raising the base tensile stress level of the Fe-SMA strip, with negligible effects on further aspects of the full-range behavior. With the increasing activation temperature, the fracture energy is initially increased and eventually reduced, while the bond capacity and effective bond length are retained almost constant.

Tailoring the porosity of chemically activated carbons derived from the HTC treatment of sewage sludge for the removal of pollutants from gaseous and aqueous phases

The management of sewage sludge is currently an open issue due to the large volume of waste to be treated and the necessity to avoid incineration or landfill disposal. Hydrothermal carbonization (HTC) has been recognized as a promising thermochemical technique to convert sewage sludge into value-added products. The hydrochar (HC) obtained can be suitable for environmental application as fuel, fertilizer, and sorbent. In this study, activated hydrochars (AHs) were prepared from sewage sludge through HTC followed by chemical activation with potassium hydroxide (KOH) and tested for the removal of pollutants in gaseous and aqueous environments, investigating carbon dioxide (CO2) and ciprofloxacin (CIP) adsorption capacity. The effects of activation temperature (550–750 °C) and KOH/HC impregnation ratio (1–3) on the produced AHs morphology and adsorption capacity were studied by Response Surface Methodology (RSM). The results of RSM analysis evidenced a maximum CO2 uptake of 71.47 mg/g for mild activation conditions (600–650 °C and KOH/HC = 1 ÷ 2), whereas the best CIP uptake of 628.61 mg/g was reached for the most severe conditions (750 °C, KOH/HC = 3). The prepared AHs were also applied for the removal of methylene blue (MB) from aqueous solutions, and the MB uptake results were used for estimating the specific surface area of AHs. High surface areas up to 1902.49 m2/g were obtained for the highest activation temperature and impregnation ratio investigated. Predictive models of CO2 and CIP uptake were developed by RSM analysis, and the optimum activation conditions for maximizing the adsorption performance together with high AH yield were identified: 586 °C and KOH/HC ratio = 1.34 for maximum yield (26.33 %) and CO2 uptake (67.31 mg/g); 715 °C and KOH/HC ratio = 1.78 for maximum yield (18.75 %) and CIP uptake (370.77 mg/g). The obtained results evidenced that chemical activation of previously HTC-treated sewage sludge is a promising way to convert waste into valuable low-cost adsorbents.

Effects of activation temperature and time on porosity features of activated carbons derived from lemon peel and preliminary hydrogen adsorption tests

Lemon peels, a common biomass waste, have an interesting composition in terms of cellulose and mineral salts that makes them good precursors for activated carbon production processes. From a circular economy perspective, this work highlights the possibility of turning a waste material into a new resource. The resulting nanostructures show interesting performance in terms of specific surface area and total pore volume, with excellent grade of microporosity, that make them suitable for various applications ranging from supercapacitors, sensors, gases separation and storage, etc. The last, and in particular hydrogen storage, represents the most interesting one. In this study the development of activated carbon through pyrolysis method, consisting of carbonization in inert ambient and subsequent physical activation in oxidizing atmosphere is reported. Influence of synthesis parameters on the porosity formation was investigated with the aim of textural properties optimization. All produced samples were initially characterized both morphologically and crystallographycally. Then, textural and adsorption properties were evaluated through volumetric apparatus. The experimental results show improvement of both textural and adsorption properties as function of synthesis parameters, developing adsorbent materials with high fraction of micropores (≃84 %), specific surface area (≃500 m2/g) and hydrogen uptake of 0.93 wt% at 77 K and 1 bar.

Heteroatom-N,S co-doped porous carbons derived from waste biomass as bifunctional materials for enhanced CO2 adsorption and conversion

Biochar, a sustainable porous material, can be modified by doping heteroatomic active sites into the skeleton to make it equip specific properties. In this work, a series of N,S co-doped porous carbons were prepared by two-step carbonization method, using waste distiller's grains as raw material and thiourea as N and S source. The effects of activation temperature, activator dosage, and thiourea dosage on the structure and CO2 uptake of porous carbons were investigated, respectively. The results showed that the prepared N,S co-doped porous carbon with the high CO2 adsorption capacity was due to abundant micropores and the high specific surface area. Notably, NSAC-(1:1)550(1) exhibited the highest CO2 uptake of 7.02 mmol·g−1 at 273.15 K and 1 bar, which was higher than that of the same type of biochar adsorbent reported in the literature. More importantly, these N,S co-doped porous carbons can also be used as a recyclable promoter for the cycloaddition of CO2 with epoxide, affording the cyclic carbonates with up to 99 % yield under solvent-free conditions. This study provides a sustainable scheme for the development of low-cost bifunctional carbon materials to achieve efficient CO2 capture and conversion.

Nickel-Alumina Catalysts for the Transformation of Vegetable Oils into Green Diesel: The Role of Preparation Method, Activation Temperature, and Reaction Conditions.

Two nickel alumina catalysts containing 60 wt. % Ni were synthesized by wet impregnation and co-precipitation in order to study the effect of preparation methods on the catalytic efficiency concerning the transformation of sunflower oil into green diesel. The effect of activation temperature on the catalytic efficiency of the most active catalyst was also studied. The catalysts were characterized using various techniques and which were evaluated in the aforementioned reaction using a semi-batch reactor. The catalyst prepared by co-precipitation exhibited a higher specific surface area and smaller mean crystal size of the nickel nanoparticle (higher nickel metallic surface). These justify its higher efficiency with respect to the corresponding catalyst synthesized by wet impregnation. The increase in the activation temperature from 400 to 600 °C increased the size of the nickel nanoparticles through sintering, thus destroying the small pores. These led to a decrease in the nickel surface and specific surface area and, thus, to a decrease in the catalytic efficiency. The optimization of the reaction conditions over the most active catalyst (prepared by co-precipitation and activated at 400 °C) leads to the complete transformation not only of the sunflower oil (edible oil) but also of waste cooking oil (non-edible oil) into green diesel. The liquid produced after the hydrotreatment for these two feedstocks for 7 h, at H2 pressure 40 bar and temperature 350 °C using 100 mL of oil and 1 g of catalyst was composed of 97 and 96 wt. % of green diesel, respectively.

High-yield preparation of B/N co-doped porous carbon nanosheets from a cross-linked boronate polymer for supercapacitor applications

B/N Co-doped carbon nanosheets (BN-CSs) are considered as the promising candidates for high-performance supercapacitors, yet high-yield preparation of such carbon nanomaterials from a boronate polymer is rarely accessed. Herein, we have demonstrated a possibility of high-yield preparation of BN-CSs by using template-free CuBr2-mediated carbonation of a cross-linked boronate polymer, which is synthesized via a solvothermal polymerization reaction between 4-formylphenylboronic acid and p-phenylenediamine. The effect of activation temperature on the morphology, specific surface area (SBET), heteroatom-doping content, and electrochemial properties of BN-CSs is discussed. It is found that CuBr2, as a mild activation reagent, not only can relieve the over-etching of carbon skeleton and B/N-bearing species, but also can react with the carbon motif via redox reaction mechanism to generate numerous pores. Consequently, the as-prepared BN-CSs present high carbon yield (>52.7 wt%), large SBET value (up to 2714.4 m2 g−1), numerous micorpores coupled with abundant and evenly-distributed B/N species (B > 1.86 at.% and N > 6.26 at.%). All these benefits contribute to the desirable electrochemical performance in both aqueous and ionic-liquid supercapacitors. When 6 M KOH aqueous solution is used as the electrolyte, the BNC-800 electrode delivers a satisfactory capacitance of 258.5 F g−1 at 0.5 A g−1, showing a certain degree of advantages when compared to reported B/N co-doped carbon materials (See Table S4). Moreover, the supercapacitors adopted a ionic-liquid electrolyte achieve a high energy density of 43.7 Wh kg−1 under the power density of 400 W kg−1. These excellent electrochemical properties coupled with both facile polymerization method and versatile CuBr2-activation strategy offer numerous possibilities for further exploration of mass B/N-rich porous polymer and carbon materials, which can be extended to a diversity of functional applications, especially in gas storage, catalysis, and batteries.

Lamellar Hierarchical Porous Carbon Prepared from Coal Tar Pitch through a Lamellar Hard Template Combined with the Precarbonization and Activation Method for Supercapacitors

The lamellar porous carbon favors the diffusion and penetration of electrolyte ions and presents a fantastic advantage as an energy storage electrode material. In this work, the lamellar Mg5(OH)4(CO3)2·4H2O template is synthesized via a simple precipitation method in the low-temperature hydrothermal condition. Lamellar hierarchical porous carbon (LHPC) is successfully synthesized through the Mg5(OH)4(CO3)2·4H2O hard template and the KOH activation method using coal tar pitch (CTP) as the carbon source. The effects of activation temperature and activator dosage on the morphology, microstructure, and supercapacitor performance are researched at length. LHPCs-1–700 displays a good lamellar structure and an abundant mesoporous structure, so as to exhibit superior capacitive performance compared with other carbon electrodes. The specific capacitance for LHPCs-1–700 reaches 298 F g–1 at 1 A g–1 and still maintains 234 F g–1 at 50 A g–1 with a high capacitance retention of 78.5% in the three-electrode system. The kinetic behavior of the LHPCs-1–700 electrode was also analyzed according to the CV data obtained at different scan rates, and it was found that the fast kinetic capacitance contribution was up to 87% at 200 mV s–1. The assembled LHPCs-1–700 symmetric supercapacitor delivered an energy density of 16.73 W h kg–1 with a power density of 859.4 W kg–1 in 1 M Na2SO4 solution. Besides, the specific capacitance retention rate could still reach 95.8% after 8000 cycles.

Activated Carbon from Stipa tenacissima for the Adsorption of Atenolol

The Stipa tenacissima S. is an endemic species of the Western Mediterranean countries, which grows on the semi-arid grounds of North Africa and South Spain. This biomass offers an abundant, renewable, and low-cost precursor for the production of activated carbon (AC). In that context, ACs were prepared by chemical activation of Stipa tenacissima leaves (STL) using phosphoric acid (H3PO4). The effects of activation temperature and impregnation ratio on the textural and chemical surface properties of the prepared activated carbons were investigated. Activation temperatures of 450 and 500 °C turned out to be the most suitable to produce activated carbons with well-developed porous textures. The best results in terms of developed surface area (1503 m2/g) and micropore volume (0.59 cm3/g) were observed for an STLs to phosphoric acid ratio of 1:2 and a carbonization temperature of 450 °C. The adsorption capacity of the optimal activated carbon was found to be 110 mg/g for the atenolol drug. The adsorption equilibrium was well explained by the pseudo-second-order model and Langmuir isotherm. This study showed that the chemical activation method using H3PO4 as an activating agent was suitable for developing STL-based activated carbon prepared for the removal of atenolol drug in an aqueous solution and compared with commercial activated carbon supplied by Darco.

Low-temperature CO oxidation on CuO-CeO2 catalyst prepared by facile one-step solvothermal synthesis: Improved activity and moisture resistance via optimizing the activation temperature

Development of a highly efficient Cu-based catalyst for low-temperature CO oxidation under moisture condition remains a grand challenge. In this paper, effect of activation temperature (350–800 °C) on catalytic performance of CuO-CeO2, prepared by facile one-step solvothermal synthesis, in CO oxidation was investigated, and the catalysts’ physicochemical properties were studied by TG-DSC, ICP-AES, N2 sorption, XRD, TEM, Raman spectroscopy, XPS, in-situ DRIFTS, H2-TPR, CO-TPD, and O2-TPD. It was found that activation at 550 °C is beneficial for the interaction between CuO and CeO2, leading to the formation of more Cu+ species and oxygen vacancies advantageous for improving the catalytic activity. Activation at 800 °C, nevertheless, would weaken the interaction between CuO and CeO2 due to the sintering of CuO and CeO2, thus decreasing the catalytic activity and moisture resistance. Interestingly, no deactivation was observed over the optimal catalyst (activated at 550 °C) after 50 h testing at a low temperature of 87 °C (at which 90% CO conversion was obtained), even when 4.2% water vapor was added into the feed gas.

Synthesis of soybean-derived porous carbon as selenium host for high-performance lithium-selenium batteries

Selenium (Se) is a promising cathode material for rechargeable lithium batteries due to its prominent volumetric capacity and relatively high electrical conductivity. However, designing a sustainable and cost-effective porous carbon as Se host in the cathode with appealing electrochemical performance is a challenge. Herein, a hierarchically porous carbon was synthesized from soybean in a carbonization/activation process and used to develop the selenium cathode material for lithium-selenium (Li-Se) batteries. The effect of activation temperature (500, 600, and 700 °C) on the porous structure of the activated carbons was investigated and correlated to the electrochemical performance of their carbon/selenium (C/Se) cathode composite in Li-Se batteries with a carbonate-based electrolyte. It was revealed that the specific surface area and pore volume of the porous carbon increased with elevating the activation temperature. The Li-Se battery using the carbon activated at 600 °C (C600) showed a superior reversible discharge capacity of 640 mAh g−1 at 0.1 C after 100 cycles, exceptional rate capability, and good long cycling stability of ∼400 mAh g−1 at 1 C over 500 cycles. The superior electrochemical performance of C600/Se cathode compared to the other samples was attributed to its microporous structure coupled with large surface area and pore volume, which could favor effective confinement of Se, electrolyte wetting, Li-ion diffusion, and accommodation of volume change. This work suggests the sustainable development of microporous carbon with a structure suitable for cathode material in Li-Se batteries.

Synthesizing Microporous Carbon from Soybean and Use It to Develop Cathode Material for High Performance Lithium-Selenium Batteries

Selenium is considered as a promising cathode material for lithium-ion batteries due to its high electrical conductivity (10−3 S m−1) and volumetric capacity (3253 mA h cm−3). Though, feasibility of high-performance lithium-selenium (Li-Se) batteries depends on designing a cost-effective substrate for Se with desired porous structure. In this study, porous carbon was synthesized from soybean in a two-step carbonization/activation process and used as Se host to develop cathode for lithium-selenium (Li-Se) batteries. The activated carbon/selenium (C/Se) composites were prepared using a melt diffusion process at 260 ℃ inside an argon-filled autoclave. The cathode material consisted of C/Se composite, carbon black, and sodium alginate with a mass ratio of 8:1:1. The effect of activation temperature (500, 600, and 700 ℃) on the porous structure of activated carbon was investigated. It was revealed that both specific surface area and pore volume increased with activation temperature. Moreover, the carbon activated at 500 ℃ (C500) possessed mainly mesopores while the pore structure in the other carbon samples was microporous. The quality of Se impregnation in C/Se composites and their distinct electrochemical performance were correlated to the porous structure of the activated carbon. Using the carbon obtained at 600 ℃ (C600), the Li-Se coin cell exhibited a superior discharge capacity (664 mAh g-1 at 0.1C current density), rate capability, and long cycling stability at higher current densities. It was believed that the microporous feature of C600 along with high surface area and pore volume could favor effective confinement of Se, electrolyte wetting of the cathode, lithium-ion diffusion, and charge transfer, which resulted in better electrochemical performance. This work suggests the sustainable development of microporous carbon with a unique structure suitable for cathode material in Li-Se batteries.

Investigation on pore structure regulation of activated carbon derived from sargassum and its application in supercapacitor

In order to realize the effective regulation of the pore structure of activated carbon and optimize its pore structure properties as electrode material, the effects of activation temperature, activation time and impregnation ratio on the specific surface area, total pore volume and average pore diameter of activated carbon prepared by sargassum are studied by orthogonal experiment. In addition, the electrochemical properties of sargassum-based activated carbon (SAC) and the relationship between the gravimetric capacitance and specific surface area of SAC are also studied. The SACs prepared under all conditions have high specific surface area (≥ 2227 m2 g−1) and developed pore structure, in which the pore diameter of micropores mainly concentrated in 0.4 ~ 0.8 nm, the pore diameter of mesopores mainly concentrated in 3 ~ 4 nm, and the number of micropores is far more than that of mesopores. In the activation process, the impregnation ratio has the greatest effect on the specific surface area of SAC, the activation temperature and impregnation ratio have significant effect on the total pore volume of SAC, and the regulation of the average pore diameter of SAC is mainly realized by adjusting the activation temperature. The SACs exhibit typical electric double layer capacitance performances on supercapacitors, delivering superior gravimetric capacitance of 237.3 F g−1 in 6 mol L−1 KOH electrolyte system at current density of 0.5 A g−1 and excellent cycling stability of capacitance retention of 92% after 10,000 cycles. A good linear relationship between gravimetric capacitance and specific surface area of SAC is observed.

Effect of thermal activation and particle size on cementitious activity of bauxite tailings.

To explore the influence of thermal activation and particle size on cementitious activity of bauxite tailings, in this study, the raw bauxite tailings were classified into coarse bauxite tailings (CBT) and fine bauxite tailings (FBT) by a powder separator, and then the effect of activation temperature on cementitious activity of CBT and FBT was investigated. XRD, TG, and FTIR were used to study the phase and structure changes of CBT and FBT during the process of thermal activation. The results show that the main mineral phases of CBT and FBT, diaspore and kaolinite, begin to remove a large amount of hydroxyl groups at 500 ℃ and convert into corundum and metakaolin, respectively. The diaspore and kaolinite have completely removed the hydroxyl groups at 600°C and 700°C, respectively. With the increase of activation temperature, the particle size of CBT and FBT are first gradually decreased, when the activation temperature exceeds 700 ℃, as the activation temperature continues to arise, the particle size of CBT and FBT are gradually increased due to the occurrence of sintering. The activity index of bauxite tailings is increased with the increase of fineness, and the optimum activation temperature of CBT and FBT is 700°C. When the activation temperature is the same, FBT has higher pozzolanic activity than CBT.