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1.
A series of super activated carbon have been prepared by potassium hydroxide activation of corncob. The as-obtained samples were characterized by SEM, TEM and N2-sorption. The results show morphologies and textural of activated carbon are highly depended on the activation temperature, heating rate, whereas the activation time is not a key factor. Morphologies and porous structure of activated carbons can be regulated by adjusting preparation parameters. A super activated carbon with BET surface area of 3530 m2/g and total pore volume of 1.94 cm3/g is obtained. However, the other activated carbon with smaller pore size exhibited the highest hydrogen uptake capacities exceeding 2.85 wt% at −196 °C and 1.0 bar, whose BET surface area is only 2988 m2/g. The correlation investigations show the micropore volume between 0.65 nm and 1.5 nm can be more important than BET surface area and total pore volume for hydrogen uptakes at −196 °C. The present results indicate that the corncob-derived activated carbons can be promising materials for hydrogen storage.  相似文献   

2.
Metal (Ni/Pd) and nitrogen codoped mesoporous templated carbons were synthesized using low‐cost surfactant‐modified mesoporous alumina as a hard template via chemical vapor deposition for hydrogen storage application. Initially, high surface area (1508 m2/g) nitrogen‐doped templated carbon was successfully prepared. Pore volume was also significant (1.64 cm3/g). The codoping with metals (Ni or Pd) reduced both the area and pore volume. All the codoped carbons were mesoporous (2‐8 nm). Aggregated morphology was observed for nitrogen‐doped carbon; tubular or noodle shape appeared on codoping with metals. The dispersion of Pd metal within the carbon framework was highest. The 2 wt% Pd codoped carbon showed the highest hydrogen uptake of 5 wt% (?196°C; 25 bar). This may be attributed to its most number of active sites corresponding to the highest metal dispersion and amount of nitrogen present. The cyclic stability of the samples was also good with only 3% to 5% loss in storage capacity up to 10 cycles.  相似文献   

3.
In this study, activated polymer-based hard carbons were prepared using various steam activation conditions in order to enhance their hydrogen storage ability. The structural characteristics of the activated carbons were observed by X-ray diffraction and Raman spectroscopy. The N2 adsorption isotherm characteristics at 77 K were confirmed by Brunauer-Emmett-Teller, Barrett-Joyner-Halenda and non-local density functional theory equations. The hydrogen storage behaviours of the activated carbons at 298 K and 10 MPa were studied using a Pressure-Composition-Temperature apparatus. From the results, specific surface areas and total pore volume of the activated carbons were determined to be 1680–2320 m2/g and 0.78–1.39 cm3/g, respectively. It was also observed that various pore size distributions were found to be dependent on the functions of activation time. In the observed result, the hydrogen adsorption of APHS-9-4 increased about 30% more than that of as-prepared hard carbon. This indicates that hydrogen storage capacity could be a function not only of specific surface area or total pore volume, but also of micropore volume fraction in the range of 0.63–0.78 nm of adsorbents.  相似文献   

4.
Porosity is a key factor for achieving superior methane (CH4) uptakes in adsorbed natural gas (ANG) applications. For preparation of carbonaceous adsorbents, physical activation is adopted on commercial production due to the simplicity of process and well-developed microporosity. However, significant challenges remained in physical activation process with low porosity. In this study, extra-porous activated carbon was prepared by additional simple silica removal process. This simple strategy provides not only extra-porosity, but also expansion of existing micropores. It should be highlighted, because of there are only few works regarding the pore expansion, whereas there have been many studies on micropore generation. Moreover, a synergetic increase in specific surface area occurs according to the proposed strategy. The synthesized materials show a high specific surface area (1343 m2/g) and CH4 uptakes of 4.25 mmol/g at 25 °C and 35 bar. This simple and prospective strategy for enhancing the textural properties provides great potential for various applications of rice husks-derived activated carbon as a porous material.  相似文献   

5.
The synthesis, characterization and hydrogen uptake of porous carbons generated by heat treatment was investigated using various zeolites and mesoporous silicas as hard templates. The effect of heat treatment on the structural order, textural properties and hydrogen uptake capacities of porous carbons templated from the model zeolite EMC-2 in a temperature range of 600–800 °C during chemical vapour deposition were studied in details. The heat treatment improved the structural order of replicated microporous carbons, significantly increased both total and microporous surface area and pore volume, and remarkably increased the hydrogen uptake capacity. The optimized heat treatment conditions were at 900 °C for 3 h. The heat treatment at high temperatures was found to be a simple and general approach to synthesize well-ordered microporous carbons from different zeolite templates, using various carbon precursors and through different synthesis methods. The microporous carbons possessed a high surface area and pore volume with increased microporosity and therefore exhibited improved hydrogen storage capacities up to 5.85 wt% at 20 bar and −196 °C. The heat treatment, however, has no obvious effect on the textural properties and hydrogen uptake capacities for mesoporous carbons templated from mesoporous silicas.  相似文献   

6.
Controlled porosity carbons aerogels were synthesized by sol–gel polycondensation of resorcinol (R) and formaldehyde (F) using sodium-carbonate as the catalyst (C). The Effect of variation of R/C ratio and carbonization temperature on the porous structure of resultant gels and carbons was investigated by characterizing the porous structure of the materials using nitrogen adsorption–desorption measurements at 77 K. It was shown that carbons with surface areas ranging between 537 and 687 m2 g?1 and average pore size in the range of 1.80–4.62 nm can be produced when controlling the resorcinol to catalyst (R/C) molar ratio between 100 and 500 and carbonization temperature in the range of 800–1000 °C.The resultant polymeric carbons were used as the electroactive material for the fabrication of electrodes for electrochemical cells. Contact angle measurements were performed to study the wettability of the electrodes using 6 M KOH as the probing liquid. The contact angles were in the range of 106°–125° indicating the carbon based electrodes are hydrophobic in nature and no significant change in contact angles was observed with the change in R/C ratio.XRD patterns of the carbon electrodes show a typical broad peak at 2θ of about 23 indicating a disordered structure corresponding to the amorphous nature of the materials as expected for polymeric based hard carbons with crosslinked structure. These results are in line with Raman spectra of carbons which indicate two peaks in 1590 cm?1 and 1340 cm?1 wavenumber.The electrochemical performance of the electrodes was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. The CV results showed that high specific capacitance of 136 Fg?1 can be achieved for the carbon with average pore diameter of 1.80 nm at a scan rate of 5 mV s?1 when using 6M KOH as the electrolyte. Electrochemical impedance (EIS) measurements also revealed that the capacitance of the cell deteriorates with increase in pore size of the carbon probably due to pore flooding by the electrolyte. The results of this study show the applicability of these carbons as potential electrode materials for supercapacitor applications.  相似文献   

7.
《Journal of power sources》2006,158(1):765-772
This work presents a systematic study on how pore size and specific surface area (SSA) of carbon effect specific capacitance and frequency response behavior. Carbide derived carbons (CDC) produced by leaching metals from TiC and ZrC at temperatures from 600 to 1200 °C have highly tailorable microstructure and porosity, allowing them to serve as excellent model systems for porous carbons in general. BET SSA and average pore size increased with synthesis temperature and was 600–2000 m2 g−1 and 0.7–1.85 nm, respectively. Maximum specific capacitance in 1 M H2SO4 was found to occur at an intermediate synthesis temperature, 800 °C, for both ZrC and TiC derived carbons and was 190 and 150 F g−1, respectively. Volumetric capacitance for TiC and ZrC derived carbons was maximum at 140 and 110 F cm−3. These results contradict an oft-reported axiom that increasing pore size and SSA, all other things being held constant, increases specific capacitance. A correlation between specific capacitance and SSA of micropores (less than 2 nm in diameter) has been shown. As expected, increasing pore size was found to improve the frequency response. However, CDCs with similar pore size distributions but obtained from different starting materials showed noticeable differences in impedance behavior. This highlights the importance of not only the pore size and specific surface area measured using gas sorption techniques, but also the pore shape or tortuousity, which is non-trivial to characterize, on energy storage.  相似文献   

8.
In this study, activated carbon is produced from defatted hazelnut bagasse at different activation conditions. The catalytic activities of activated carbons are evaluated for NaBH4 methanolysis and electrooxidation. These materials are characterized by N2 adsorption-desorption, FTIR, SEM-EDS and XPS and results show that these materials are prepared successfully. N2 adsorption-desorption results reveal that activated carbon (FH3-500) has the highest BET surface area as 548 m2/g, total pore volume as 0.367 cm3/g and micropore volume as 0.205 cm3/g. On the orher hand, as a result of hydrogen production studies, FH3-500 activated carbon catalyst has the highest initial hydrogen production rate compared to other materials. At 50 °C, this metal-free activated carbon catalyst has a high initial hydrogen production rate of 13591.20 mL/min.gcat, which is higher than literature values. Sodium borohydride electrooxidation measurements reveal that FH2-500 also has the highest electrocatalytic activity and stability. Hazelnut pulp-based activated carbons are firstly used as a metal-free catalyst in the methanolysis and electrooxidation of sodium borohydride, and its catalytic activity is good as a metal-free catalyst. The results show that the hazelnut pulp-based activated carbon catalyst is promising as a metal-free catalyst for the methanolysis and electrooxidation of sodium borohydride.  相似文献   

9.
Challenges in removal of contaminants, especially tars, from biomass-generated producer gas continue to hinder commercialization efforts in biomass gasification. The objectives of this study were to synthesize catalysts made from biochar, a byproduct of biomass gasification and to evaluate their performance for tar removal. The three catalysts selected for this study were original biochar, activated carbon, and acidic surface activated carbon derived from biochar. Experiments were carried out in a fixed bed tubular catalytic reactor at temperatures of 700 and 800 °C using toluene as a model tar compound to measure effectiveness of the catalysts to remove tar. Steam was supplied to promote reforming reactions of tar. Results showed that all three catalysts were effective in toluene removal with removal efficiency of 69–92%. Activated carbon catalysts resulted in higher toluene removal because of their higher surface area (∼900 m2/g compared to less than 10 m2/g of biochar), larger pore diameter (19 A° compared to 15.5 A° of biochar) and larger pore volume (0.44 cc/g compared to 0.085 cc/g of biochar). An increase in reactor temperature from 700 to 800 °C resulted in 3–10% increase in toluene removal efficiency. Activated carbons had higher toluene removal efficiency compared to biochar catalysts.  相似文献   

10.
While the challenge of storing hydrogen in inexpensive and renewable adsorbents is relentlessly pursued by researchers all over the world, application of hydrochar derived from biomass is also gaining attention as it can be subsequently chemically activated using activating agents like KOH in order to tailor the development of favorable porosity. However, the synergistic effect of hydrothermal carbonization (HTC) process conditions as well as KOH activating conditions on the development of surface morphology is required to be assessed with the application of such porous superactivated hydrochars in hydrogen storage application. In this study, highly porous superactivated hydrochars were fabricated from inexpensive and abundant loblolly pine. Loblolly pine was hydrothermally carbonized at 180 °C, 220 °C and 260 °C and the hydrochars were then activated at different experimental conditions of 700 °C, 800 °C and 900 °C using solid KOH to loblolly pine hydrochar ratio of 2:1, 3:1 and 4:1 to produce superactivated hydrochars. Superactivated hydrochars as well as loblolly pine and its corresponding hydrochars underwent physicochemical analysis as well as surface morphology analysis by SEM and nitrogen adsorption isotherms at 77 K in order to investigate the effect on BET, pore volume, and pore size distribution due to various process conditions. The superactivated hydrochars were then analyzed to quantify total hydrogen storage capacity of these materials at 77 K and up to pressure of 55 bar. Porosity of superactivated hydrochars were as high as 3666 m2/g of BET specific surface area (SSA), total pore volume of 1.56 cm3/g and micropore volume of 1.32 cm3/g with the hydrogen storage capacity of 10.2 wt% at 77 K and 55 bar. It was conclusive from principal component analysis that higher HTC temperature with moderate activation condition demonstrated favorability in developing porous superactivated hydrochars for hydrogen storage applications.  相似文献   

11.
Biomass based carbon has captured more and more attention because it is environmentally friendly and has properties of low cost and ideal sustainability. In this study, three kinds of activated biomass carbons (ie, ABC-700, ABC-800 and ABC-900) were first carbonized through pine sawdust pyrolysis and then activated using KOH under three different activation temperatures (ie, 700°C, 800°C and 900°C). The structure properties of the prepared activated biomass carbons were characterized by N2-adsorption/desorption, SEM, TEM, XRD, Raman, XPS, TG and ultimate analysis. To clarify the activation mechanism, the gas products produced during KOH activation process were measured online with an ETG gas analyzer. The performance of the activated biomass carbons derived from pine sawdust for supercapacitor and CO2 capture was then evaluated. The predominant gas products during the activation process are H2 and CO. It indicates that the porous structure was created by using an enhanced etching reaction between carbon atoms and KOH. An increment of the activation temperature from 700 to 900°C results in the increase of surface area (from 1728.66 to 2330.89 m2/g) and total pore volume (from 0.671 to 1.914 cm3/g). Among the three samples, ABC-900 exhibits the maximal specific capacitance of 175.6 F·g−1 and high energy density of 24.39 Wh·kg−1 at the 0.5 A·g−1. And the ABC-700 shows the maximal CO2 capture capacity of 4.21 mmol/g and high selectivity of CO2 over N2 at 298 K and 1 bar. In addition, ABC-700 also has excellent stability and reproducibility after 15 times adsorption-desorption cycles. The unexceptionable electrochemical performance and adsorption capacity of the biomass-carbons show its broad application prospects in the field of supercapacitors and CO2 capture.  相似文献   

12.
Current concerns with the high energy/cost nature of activated carbon production have encouraged research into alternative activated carbon production methods to reduce the environmental impact. The purpose of this study is to produce the activated carbon from biomass (carob bean seed husk, CBSH) by chemical activation with a different methodology using zinc chloride. Two different activation temperature methodologies for the preparation of activated carbons were applied at the ranges of 30–80 and 200–350°C. The effects of the pre-activation and activation temperatures, duration time, and the impregnation ratio on the surface and chemical properties of activated carbon were investigated. Studies were conducted on the adsorption of iodine from the prepared activated carbon. The highest iodine adsorption number was achieved as 874 mg/g. Langmuir surface area was 1544 m2/g. The structural morphology of activated carbons was evaluated with a scanning electron microscope. The surface chemical characteristics of activated carbons were determined by the Fourier transform infrared (FTIR) spectroscopic method.  相似文献   

13.
《Energy Conversion and Management》2001,42(15-17):2005-2018
Catalytic oxidation of NO to NO2 over activated carbons PAN-ACF, pitch-ACF and coconut-AC at room temperature (30°C) were studied to develop a method based on oxidative removal of NO from flue gases. For a dry gas, under the conditions of a gas space flow rate 1500 h−1 in the presence of oxygen of 2–20% in volume concentration, the activated coconut carbon with a surface area 1200 m2/g converted about 81–94% of NO with increasing oxygen concentration, the pitch based activated carbon fiber with a surface area 1000 m2/g about 44–75%, and the polyacrylonitriale-based activated carbon fiber with a surface area 1810 m2/g about 25–68%. The order of activity of the activated carbons was PAN-ACF<pitch-ACF<coconut-AC. However, NO conversion markedly decreased with the increases in temperature and humidity. For the dry gas, the apparent reaction rate was expressed by an equation: R=kcPNOPO2β (F/W), where β is 0.042, 0.16, 0.31 for the coconut-AC, the pitch-ACF and the PAN-ACF respectively, and kc is 0.94 at 30°C.  相似文献   

14.
In the present study, using modelling based on experimental data, models for predicting the hydrogen adsorption isotherm were presented. The three Automatic Learning of Algebraic Models (ALAMO), feed-forward artificial neural networks (ANNs), and group method of data handling-type polynomial neural networks (GMDH-PNN) were constructed. The created models were evaluated to predict the equilibrium data of hydrogen storage on carbon nanostructures, including activated carbons doped with palladium (Pd) nanoparticles, fullerene pillared graphene nanocomposites, and nickel (Ni)-decorated carbon nanotubes. The inputs were nanostructure characteristics such as surface area, pore-volume, and thermodynamic conditions such as pressure. The generalization of the trained models was acceptable, and the models successfully predicted the hydrogen adsorption isotherm for new inputs. The relative error percentage for most data points is less than 4%, which demonstrates their applicability in determining adsorption isotherms for any operating conditions. By performing error analysis calculations, it was shown that the ALAMO model has the highest accuracy. Also, sensitivity analysis calculations show that pressure is the most influential parameter in the adsorption process. Besides, by performing Genetic Algorithm (GA) optimization using the ALAMO model, the amount of pressure and adsorbent properties were determined so that the amount of hydrogen adsorption is maximized. According to the optimization results based on the GA, the higher the pressure, the greater the amount of hydrogen adsorption. The nanotubes with a surface area of 194.15 m2/g, a total volume of 1.8 cm3/g, micropore volume of 0.097 cm3/g, and mesopore volume of 0.963 cm3/g, graphene with a surface area of 2977.13 m2/g, a total volume of 1.5134 cm3/g, density of 617.45 kg/m3, and activated carbon at pressures less than 30 bar with a surface of 2546.36 m2/g, a total volume of 1.237 cm3/g, micropore volume of 0.839 cm3/g, and activated carbon at pressures more than 30 bar with a surface of 3027 m2/g, a total volume of 1.343 cm3/g, a micropore volume of 0.9582 cm3/g, and a mesopore volume of 1.23 cm3/g, have the highest amount of stored hydrogen.  相似文献   

15.
In order to investigate the catalytic capacity of metals and metal oxides based on electrospun carbon fibers for improving hydrogen storage, electrospinning and heat treatments were carried out to obtain metal/metal oxide-embedded carbon fibers. Although the fibers were treated with the same activation procedure, they had different pore structures, due to the nature of the metal oxide. When comparing the catalytic capacity of metal and metal oxide, metal exhibits better performance as a catalyst for the improvement of hydrogen storage, when considering the hydrogen storage system. When a metal oxide with an m.p. lower than the temperature of heat treatment was used, the metal oxide was changed to metal during the heat treatment, developing a micropore structure. The activation process produced a high specific surface area of up to 2900 m2/g and a pore volume of up to 2.5 cc/g. The amount of hydrogen adsorption reached approximately 3 wt% at 100 bar and room temperature.  相似文献   

16.
《Journal of power sources》2004,133(2):329-336
The behavior of two types of mesoporous carbons with different pore structures (i.e. unimodal and bimodal) as electrode material in an electrochemical double-layer capacitor has been analyzed. The carbon samples were prepared using mesostructured silica materials (MSM) as templating agents. The unimodal mesoporous carbon has a BET surface area of 1550 m2 g−1, and a pore volume of 1.03 cm3 g−1; the porosity is mainly made up of structural mesopores of ca. 3 nm that exhibit a narrow pore size distribution (PSD). The bimodal carbon shows larger surface area (1730 m2 g−1) and larger pore volume (1.50 cm3 g−1); the porosity is composed of two types of mesopores: structural (size around 3 nm) and complementary (size around 16 nm) mesopores. Both carbons show a disordered 3-D pore structure. Heat treatments at high temperatures (1000 °C) for long times (11 h) do not significantly change the pore structure with respect to the two synthesised carbons (800 °C). From the synthesized and heat-treated carbons, electrodes were processed as composites in which the carbons, polivinilidene fluoride (PVDF) and carbon black (CB) were the components. The effect of the heat treatment and relative CB content on specific capacitance, energy density and power density were studied. We found a specific capacitance of 200 F g−1 for low current density (1 mA cm−2) and 110 F g−1 for high current density (150 mA cm2). Moreover, the curve of the specific capacitance versus current density shows three regimes, which are related to the three types of pore: micropores, structural mesopores and complementary mesopores. An energy density of 3 Wh kg−1 at a power density of 300 W kg−1 was obtained in some particular cases.  相似文献   

17.
Porous carbons as electrode materials are highly desired for use in energy storage/conversion devices. Herein, the development of a series of highly porous nitrogen and oxygen co-doped carbons by using pea protein (PP) as a cost-effective, sustainable and nitrogen-rich precursor is reported. Pea protein derived carbons (PPDCs) have been prepared by applying a straightforward two-step synthetic route including pyrolysis and KOH-chemical activation. Potassium hydroxide has been employed to generate porosity and introduce oxygen functionalities into the framework of carbon. The heteroatoms doping content and porosity parameters have been tuned by varying the synthesis temperature and activator to precursor ratio. The carbon obtained with optimal synthetic parameters (T = 800 °C and KOH/Precursor = 4) featured the highest surface area, the maximal pore volume and N-/O doping level of 3500 m2 g?1, 1.76 cm3 g?1, and 2.5-/17.9 at%, respectively. PPDC-4-800 as supercapacitor presented a very high specific capacitance (413 F g?1 at 1.0 A g?1 in 1 M KOH), remarkable cycling stability (92% retention after 20000 cycles) and outstanding rate capability (210 F g?1 at 30 A g?1). The cooperative effects of the well-developed porous architecture and surface modification of PPDCs resulted in enhanced electrochemical performances, suggesting their potential application for energy storage devices.  相似文献   

18.
《Applied Thermal Engineering》2007,27(7):1212-1218
The purpose of this research is to obtain optimal processing conditions for activated carbon from lignite by chemical activation with K2CO3 using response surface methodology (RSM). The activated carbons produced were characterized by carbon yield (%), BET surface area, porosity development (total pore volume and micropore fraction). RSM based on a five-variable central composite rotatable design was used to determine the effect of chemical ratio (ranging from 0 to 4) and activation temperature (ranging from 500 °C to 900 °C) on the responses levels. Each response has been described by a second order model that was found to be appropriate to predict most of the responses in every experimental region. The most influential factor on each experimental design response have been identified from the analysis of variance (ANOVA). The optimum conditions for manufacturing of activated carbon from Turkish lignite, which were based on response surface and contour plots, were found as follows: chemical ratio of 2.05 and carbonization temperature of 800 °C.  相似文献   

19.
《Biomass & bioenergy》2006,30(2):144-152
Biomass waste in the form of biomass flax fibre, produced as a by-product of the textile industry was processed via both physical and chemical activation to produce activated carbons. The surface area of the physically activated carbons were up to 840 m2 g−1 and the carbons were of mesoporous structure. Chemical activation using zinc chloride produced high surface area activated carbons up to 2400 m2 g−1 and the pore size distribution was mainly microporous. However, the process conditions of temperature and zinc chloride concentration could be used to manipulate the surface area and porosity of the carbons to produce microporous, mesoporous and mixed microporous/mesoporous activated carbons. The physically activated carbons were found to be a mixture of Type I and Type IV carbons and the chemically activated carbons were found to be mainly Type I carbons. The development of surface morphology of physically and chemically activated carbons observed via scanning electron microscopy showed that physical activation produced activated carbons with a nodular and pitted surface morphology whereas activated carbons produced through chemical activation had a smooth surface morphology. Transmission electron microscopy analysis could identify mesopore structures in the physically activated carbon and microporous structures in the chemically activated carbons.  相似文献   

20.
Sliced activated carbons were prepared from palm tree fronds, a biomass material, using a single step physical method. Effect of the synthetic parameters on the surface area, pore size and pore volume of the activated carbon were studied, pursuing by the optimization of studied parameters. The activation temperature, heating ramp rate, reaction vessel pressure and the CO2 flowrate were found to be the influential parameters for the synthesis of sliced activated carbon with larger porosity and surface area. The optimum conditions to synthesize the porous activated carbon bearing high pore volume and surface area were studied and identified. Highest surface area of 1094 m2 g−1 was achieved under the optimum conditions. Scanning electron microscopy (SEM) for the porosity and Fourier transform infrared spectroscopy (FTIR) for surface functional groups and transmission electron microscopy (TEM) confirms the presence of uniform nanoparticles of 2.1385 nm.  相似文献   

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