Pore Size Distribution Of Carbon Research Articles

Asymmetric capacitive deionization based on pore structures of biochar

Biochar is an affordable and sustainable material for the application of capacitive deionization. Although the desalination capability of biochar is significantly impacted by its pore size distribution, the correlation between them is challenging to explore due to the uncontrollable pore size. This study exclusively utilizes different activation mechanisms to regulate the pore size distribution of carbon derived from the same biomass precursor, and explores the role of pore structures in capacitive deionization. The specific capacitance of microporous biochar (MiB) can reach up to 319.1 F/g (0.2 A/g), with an Epzc of 0.11 V and high oxygen content, while mesoporous biochar (MeB) has a specific capacitance of only 170.4 F/g, an Epzc of 0 V, and a small charge transfer impedance. The MeB//MiB desalination cell is designed based on these characteristics and demonstrates a higher salt adsorption capacity of 17.04 mg/g at 1.2 V, compared to MiB//MiB (15.72 mg/g) and MeB//MeB (6.07 mg/g), alongside a stability of 81 % after 50 cycles. These capabilities can be attributed to the expanded voltage range resulting from the different Epzc, and the high ion storage capacity of MiB, as well as the fast ion transport capability of MeB. The oxygen/carbon ratio of the anode in MeB//MiB increased by only 42 %, whereas that in MiB//MiB increased by 370 %, confirming the oxidation inhabitation ability of the asymmetric structure and the oxidation resistance of MeB. Therefore, constructing ideal pore structures and more importantly reasonable deployment is an effective strategy for improving desalination capacity and stability.

A reign of bio-mass derived carbon with the synergy of energy storage and biomedical applications

The high specific surface area and suitable pore size distribution of carbon based electrodes significantly improves the energy and power density of energy storage devices. The present study details the development of eco-friendly and low-cost carbon material containing fluorine (F) atoms prepared from biomass Ipomoea carnea flower (IC). The favourably developed carbon material is used as electrode for lithium‑sulfur batteries (LSBs), supercapacitors and biomedical application of the same is explored. Owing to its high theoretical specific capacity, high energy density and low production cost, LSBs are recognised as propitious class of energy storage devices. The detriments like fast capacity fading arising due to insulating nature, shuttle effect and volume expansion of sulfur electrode is surmount by employing ternary composite of sulfur/silicon dioxide/IC (SSIC) as cathode for LSBs. The outcome of this work reveals that polysulfides are confined both physically and chemically by highly electronegative F atoms present in IC along with SiO2, thereby alleviating shuttle effect and demonstrates better electrochemical performance. SIC electrode exhibited a coulombic efficiency of 95%, whereas SSIC electrode delivered efficiency of 99.5% after entire cycling life. Here, IC carbon matrix is also employed as electrode material for supercapacitor device which delivered specific capacitance up to 382 F g−1 which is outstanding when compared to capacitances from other reported carbon supercapacitors. The cytotoxicity of IC carbon is analysed by co-culturing IC carbon with human breast cancer cells (MCF-7 cell line). The cell death is observed in the IC50 concentration of 56.23 μg/ mL.

Favorable pore size distribution of biomass-derived N, S dual-doped carbon materials for advanced oxygen reduction reaction

Metal-free carbon materials offer prominent performance towards the oxygen reduction reaction (ORR). The pore size distribution of carbons plays the vital role in promoting the electrocatalytic property. Herein, a succession of N, S dual-doped carbons decorated with 3D interpenetrated hierarchically porous structure are successfully obtained through utilizing ZnCl 2 and Zn(OH) 2 as porogens during carbonizing biomass-wastes. The nanopore amounts with specific sizes can be manipulated through changing diverse biomass-wastes as precursors, while different pore sizes can be optimized by tuning the dosage ratios of ZnCl 2 to Zn(OH) 2 . Accompany with the increased amounts of nanopores with sizes of 4.6, 12, 17 and 27 nm, the ORR activity of carbon materials has been significantly promoted. These suitable pore sizes ensure the highly effecient mass transfer through providing abundantly accessible delivery channels and reactive zones for ORR-related intermediates. The optimized catalyst delivers the excellent ORR activity with a half-wave potential of 0.83 V vs. RHE as well as the remarkable long-term stability and methanol resistance ability in alkaline medium. Moreover, two series-connected Zn-air batteries with the catalysts can continuously lighten 216 LEDs over 24 h. The application of biomass-wastes to synthesize N, S dual-doped hierarchical porous carbons is beneficial for achieving the goals of turning waste into treasure. The amounts of pores with sizes of 4, 12, 17 and 27 nm show an apparent control on ORR activity according to biomass-wastes derived carbon materials, achieving the goals of turning waste into treasure and providing a rational guidance in preparing the high-performance electrocatalysts. • Continuously regulating the nanopore amount of carbon materials has been achieved. • The application of biomass-wastes realizes the goal of turning waste into treasure. • The optimized catalyst delivers the impressive ORR catalytic activity. • The assembled Zn-air battery continuously drives 216 LEDs for 24 h. • This work identifies the favorable pore size of carbon materials towards ORR.

Novel Insight into the Concept of Favorable Combination of Electrodes in High Voltage Supercapacitors: Toward Ultrahigh Volumetric Energy Density and Outstanding Rate Capability.

Most of the biomass‐derived carbon‐based supercapacitors using organic electrolytes exhibit very low energy density due to their low operating potential range between 2.7 and 3.0 V. A novel insight into the concept of the different porous architecture of electrode materials that is employed to extend a device's operating potential up to 3.4 V using TEABF4 in acetonitrile, is reported. The combination of two high surface area activated carbons derived from abundant natural resources such as industrial waste cotton and wheat flour as sustainable and green carbon precursors is explored as an economical and efficient supercapacitor carbon electrode. Benefitting from the simultaneous achievement of the higher potential window (3.4 V) with higher volumetric capacitance (101 F cm–3), the supercapacitor electrodes exhibit higher volumetric energy density (42.85 Wh L–1). Bimodal pore size distribution of carbon with a tuned pore size and high specific surface area of the electrode can promote the fast transport of cations and anions. Hence, it exhibits a high rate capability even at 30 A g–1. In addition, the electrodes remain stable during operation cell voltage at 3.4 V upon 15 000 charging–discharging cycles with 90% capacitance retention.

Monte Carlo simulation method for calculating pore size distributions from high-pressure CO2 adsorption in Micro-Mesoporous Carbons

An original methodology is suggested for evaluating the pore size distribution in carbons in the wide range of micro- and mesopores from 0.385 to 10 nm from a single isotherm of high-pressure adsorption of CO2 at 273 K. The proposed method is based on the reference theoretical isotherms calculated by Monte Carlo simulations in model pores of slit and cylindrical geometry. The relationship between the pore size and the pore filling pressure is established. Special attention is given to predicting of the capillary condensation transitions in mesopores by using the meso-canonical ensemble (gauge cell) Monte Carlo simulations. The proposed technique is demonstrated and verified against the conventional N2 and Ar low temperature adsorption methods drawing on the example of micro-mesoporous carbons of the CMK family. Advantages and limitations of CO2 adsorption characterization of nanoporous materials are discussed and further improvements are proposed.

Pore size characterization of micro-mesoporous carbons using CO2 adsorption

Pore structure characterization plays a crucial role in the optimization of adsorption properties of nanoporous carbons employed for water purification, gas and liquid phase separations, carbon dioxide reduction, energy storage, and other applications. Here, we present an original methodology for evaluating the pore size distribution in carbons in a wide range of micro- and mesopores from 0.385 to 10 nm from a single isotherm of high-pressure adsorption of CO2 at 273 K. The proposed method is based on the reference theoretical isotherms calculated by Monte Carlo simulations in model pores of slit-shaped and cylindrical geometry. The relationship between the pore size and the pore filling pressure is established. Special attention is given to the predicting of the capillary condensation transitions in mesopores by using the meso-canonical ensemble (gauge cell) Monte Carlo simulations. The proposed technique is demonstrated and verified against the conventional N2 and Ar low temperature adsorption methods drawing on the example of micro-mesoporous carbons of the CMK family. Advantages and limitations of CO2 adsorption characterization of nanoporous materials are discussed and further improvements are proposed.

Exploiting the adsorption of simple gases O2 and H2 with minimal quadrupole moments for the dual gas characterization of nanoporous carbons using 2D-NLDFT models

For years, the characterization of carbon pore size distribution (PSD) has been dominated by the analysis of N2 isotherms. Recently, the IUPAC Technical Report (2015) recommended Ar as inert gas for this analysis. N2 molecule due to its significant quadrupole moment may selectively interact with the polar surface sites and affect the isotherm measurement. CO2, another gas that is often used for the characterization of microporous carbons exhibits even higher quadrupole moment than N2. In the present study, we substitute N2 and CO2 with O2 and H2 gases that have much lower quadrupole moments. The PSD calculations are performed using molecular models based on classical and quantum corrected two-dimensional nonlocal density functional theory (2D-NLDFT).We compare the results of the dual gas analysis methods by the simultaneous fit of our models to N2 & CO2, and O2 & H2 isotherms for several reference carbon samples and demonstrate consistency between the results derived from both pairs of isotherms.A fundamental and practical benefit of using the dual gas analysis method is the ability to obtain the full micro and mesopore PSD by using a partial O2 isotherm without low-pressure data in combination with full H2 isotherm both measured at 77 K.

Activated Carbon Based Quasi-Reference Electrodes for Unconventional Lithium-Salt Containing Organic Electrolytes

Metallic lithium is the most frequently employed reference electrode in lithium ion battery research, but its high reactivity limits its utilization mainly to conventional carbonate based electrolytes. Novel concepts, like hybrid battery/supercapacitor devices, are often based on electrolytes with high ionic conductivity (e.g., acetonitrile). The utilization of these electrolytes brings up its own challenges as fundamental electrochemical characterizations are drastically aggravated by the high reactivity towards lithium metal. An alternative to Li/Li+ reference electrode for TEA-BF4 containing organic electrolytes is PTFE bound activated carbon as was shown in 2009.1 However, the latter approach yielded a pronounced drift of the reference electrode potential over time when a lithium-salt was employed. This effect is only poorly understood so far and a stable reference electrode for such systems is in high demand. Based on these issues, we provide a comprehensive study to establish (modified) carbon as a stable quasi-reference electrode for advanced lithium-salt containing electrolytes.2 In our work, we investigate the suitability of different carbons as quasi-reference electrodes (QREs) for lithium-salt containing electrolytes. As a reference point, we directly use the lithium intercalation/de-intercalation reaction of nanoparticulate Li4Ti5O12. Low surface area carbon-based QREs are impaired by high rates of potential shift (140 mV after 5 d). All high surface area carbon-based QREs show very low, uniform, and reproducible rates of potential shift (40-50 mV after 5 d). Only a negligible influence of carbon pore size distribution, electrolyte solvent, and binder on the reference electrode stability was observed. A distinct influence of the electrolyte anion on the quasi-reference electrode stability was found (Figure 1). The stability of pristine activated carbon decreases in the following order LiTFSI>LiClO4>LiPF6>LiBF4. We also studied the influence of carbon modification on the QRE stability. Activated carbon was de-functionalized (thermal annealing in vacuum or hydrogen) and functionalized (HNO3 treated) in order to unveil coherences of reference electrode stability with surface functional groups. The potential shift of activated carbon is drastically suppressed if the carbon surface is saturated by oxygen and nitrogen functional groups (Figure 2). After 15 days, the potential of heavily functionalized activated carbon is only marginally altered by 10 mV. Therefore functionalized activated carbon is a well suited quasi-reference electrode for the electrochemical characterization of Li-salt containing electrolytes which are not stable versus lithium metal.

In-situ Pd–Pt nanoalloys growth in confined carbon spaces and their interactions with hydrogen

Optimized synthesis of Pd–Pt nanoalloys confined in mesoporous carbons by a simple and fast one-pot microwave assisted approach is reported herein. The influence of several synthetic parameters (Pd–Pt composition, cross-linker type, Pd precursor type and its addition time) on the carbon framework and Pd–Pt nanoparticles formation and characteristics was investigated. Small and uniform distributed nanoparticles on tailored mesoporous carbons are obtained in short time compared to the classical approaches. The metallic composition has a great influence on the nanoparticle size and an important effect on the carbon pore size distribution. When Pt content increases (from 10 to 90 at.%), an increase in the particle size (from 6.5 to 18 nm) and in the pore size distribution of the carbon support (from 3 to 13 nm) is observed. Bulk immiscible Pd–Pt alloys were formed in the whole composition range as highlighted by the linear relationship between the lattice parameter and the metal content. The Pd precursor, the cross-linker and the addition time proved to have a significant effect in the final size/shape of the Pd–Pt nanoparticles.The optimized synthetic method can successfully tailor the size and the confinement of nanoparticles into the carbon matrix. Consequently, the hydrogen absorption properties and hydride formation can be tuned by the particle size for the richest Pd-composition nanoalloy (Pd90Pt10). The smaller Pd–Pt nanoparticles (6 to 20 nm) are confined in the carbon matrix and are surrounded by a graphitic layer preventing the hydrogen absorption while larger particles (50 nm) absorb hydrogen with metal hydride formation.

Complementary surface charge for enhanced capacitive deionization

Commercially available activated carbon cloth electrodes are treated using nitric acid and ethylenediamine solutions, resulting in chemical surface charge enhanced carbon electrodes for capacitive deionization (CDI) applications. Surface charge enhanced electrodes are then configured in a CDI cell to examine their salt removal at a fixed charging voltage and both reduced and opposite polarity discharge voltages, and subsequently compared to the salt removal of untreated electrodes. Substantially improved salt removal due to chemical surface charge and the use of a discharge voltage of opposite sign to the charging voltage is clearly demonstrated in these CDI cycling tests, an observation which for the first time validates both enhanced CDI and extended-voltage CDI effects predicted by the Donnan model [Biesheuvel et al., Colloids Interf. Sci. Comm., 10.1016/j.colcom.2015.12.001 (2016)]. Our experimental and theoretical results demonstrate that the use of carbon electrodes with optimized chemical surface charge can extend the CDI working voltage window through discharge voltages of opposite sign to the charging voltage, which can significantly enhance the salt adsorption capacity of CDI electrodes. Thus, in addition to carbon pore size distribution, chemical surface charge in carbon micropores is considered foundational for salt removal in CDI cells.

Dual gas analysis of microporous carbons using 2D-NLDFT heterogeneous surface model and combined adsorption data of N2 and CO2

Knowledge of the pore structure of carbon materials including micropores is crucial for applications such as double layer supercapacitors, gas separation, and other applications requiring high specific surface area materials. High surface area is always associated with fine micropores. The pore size distribution (PSD) of microporous carbons is usually evaluated from nitrogen adsorption isotherms measured at 77K in the relative pressure range from 10−7 to 1. Due to the very slow gas diffusion into fine pores at cryogenic temperatures and low pressures, the adsorption measurements may be extremely time consuming and sometimes inaccurate when the adsorption equilibrium is difficult to achieve during the measurement. In this work, we discuss an approach in which the carbon PSD is calculated from the combined N2 and CO2 data measured in the pressure range from 1 to 760Torr. Under such conditions, the diffusion into micropores is usually fast and equilibration times are short for both measurements. In the PSD calculations we use 2D-NLDFT models for carbons with heterogeneous surfaces (J. Jagiello and J.P. Olivier, Adsorption19, 2013, 777–783). We show that both isotherms can be fitted simultaneously with their corresponding models and as a result the unified PSD can be obtained.

Molecular simulation of the accumulation of alkanes from natural gas in carbonaceous materials

The accumulation of heavier alkanes is a significant drawback in the use of activated carbon for the storage of natural gas. Thus far, no predictive method has been developed that can describe bed deactivation beforehand. We propose a new methodology that uses atomistic simulation and only carbon pore size distribution as the input to predict bed deactivation caused by natural-gas alkanes. We validated our model by comparing the calculated results with experimental data for alkane monocomponent isotherms and bed deactivation for WV 1050 activated carbon. Using this methodology, we estimated bed deactivation for three other species of activated carbon (Maxsorb, BPL and Norit R1) within the values found in the literature. We then predicted the optimal pore size for achieving maximum storage capacity and for minimizing the retention of heavier fractions. The suggested method will assist both fast screening and new synthesis routes for carbonaceous materials with diminished heavier-alkane selectivity. Carbon-based adsorbents used in CO2 removal during the processing of raw natural gas can also be improved.

The effects of the surface oxidation of activated carbon, the solution pH and the temperature on adsorption of ibuprofen

A commercial microporous–mesoporous granular activated carbon was modified by oxidation with either H2O2 in the presence or absence of ultrasonic irradiation, or NaOCl or by a thermal treatment under nitrogen flow. Raw and modified materials were characterized by N2 adsorption–desorption measurements at 77K, Boehm titrations, pH measurements and X-ray photoelectron spectroscopy. Ibuprofen adsorption kinetic and isotherm studies were carried out at pH 3 and 7 on raw and modified materials. The thermodynamic parameters of adsorption were calculated from the isotherms obtained at 298, 313 and 328K. The pore size distribution of carbon loaded with ibuprofen brought out that adsorption occurred preferentially into the ultramicropores. The adsorption of ibuprofen on pristine activated carbon was found endothermic, spontaneous (ΔG°=−1.1kJmol−1), and promoted at acidic pH through dispersive interactions. All explored oxidative treatments led mainly to the formation of carbonyl groups and in a less extent to lactonic and carboxylic groups. This then helped to enhance the adsorption uptake while decreasing adsorption Gibbs energy (notably −7.3kJmol−1 after sonication in H2O2). The decrease of the adsorption capacity after bleaching was attributed to the presence of phenolic groups.

The effects of dissolved natural organic matter on the adsorption of synthetic organic chemicals by activated carbons and carbon nanotubes

Understanding the influence of natural organic matter (NOM) on synthetic organic contaminant (SOC) adsorption by carbon nanotubes (CNTs) is important for assessing the environmental implications of accidental CNT release and spill to natural waters, and their potential use as adsorbents in engineered systems. In this study, adsorption of two SOCs by three single-walled carbon nanotubes (SWNTs), one multi-walled carbon nanotube (MWNT), a microporous activated carbon fiber (ACF) [i.e., ACF10] and a bimodal porous granular activated carbon (GAC) [i.e., HD4000] was compared in the presence and absence of NOM. The NOM effect was found to depend strongly on the pore size distribution of carbons. Minimal NOM effect occurred on the macroporous MWNT, whereas severe NOM effects were observed on the microporous HD4000 and ACF10. Although the single-solute adsorption capacities of the SWNTs were much lower than those of HD4000, in the presence of NOM the SWNTs exhibited adsorption capacities similar to those of HD4000. Therefore, if released into natural waters, SWNTs can behave like an activated carbon, and will be able to adsorb, carry, and transfer SOCs to other systems. However, from an engineering application perspective, CNTs did not exhibit a major advantage, in terms of adsorption capacities, over the GAC and ACF. The NOM effect was also found to depend on molecular properties of SOCs. NOM competition was more severe on the adsorption of 2-phenylphenol, a nonplanar and hydrophilic SOC, than phenanthrene, a planar and hydrophobic SOC, tested in this study. In terms of surface chemistry, both adsorption affinity to SOCs and NOM effect on SOC adsorption were enhanced with increasing hydrophobicity of the SWNTs.

Pore Size Distribution of Carbon with Different Probe Molecules

In this study, a Grand Canonical Monte Carlo simulation (GCMC) method is used to study the adsorption of different probe molecules on activated carbon, while the experimental tests are performed by using a Gravimetric Analyzer. In addition the simulation results together with the measured isotherm data are used for the determination of micropore size distribution. Nitrogen at 77 K and carbon dioxide at 273 and 300 K are proposed as molecular probes. The simulation results obtained for various pore sizes represent the structure of molecular probe packing in the individual pores at different pressures. The reconstructed adsorption isotherm obtained by using these results and a postulated pore size distribution (PSD) function is used to determine the PSD of activated carbon which provides the best match between the simulation isotherm and the experimental isotherm. The PSD obtained using the GCMC agrees very well with the Density Functional Theory (DFT) method. The PSD for carbon dioxide differs from that for nitrogen due to the molecular structure and size. The advantage of GCMC is that it can provide not only adsorption isotherm but also the snapshot that presents the mechanism inside the pore.

Effects of Powdered Activated Carbon Pore Size Distribution on the Competitive Adsorption of Aqueous Atrazine and Natural Organic Matter

The pore size distribution (PSD) of adsorbents has been found to be an important factor that affects adsorption capacity for organic compounds; consequently, it should influence competitive adsorption in multisolute systems. This research was conducted to show howthe PSD of activated carbon affects the competition between natural organic matter (NOM) and the trace organic contaminant atrazine, with a primary emphasis on quantifying the pore blocking mechanism of NOM competition. Isotherm tests were performed for both atrazine and NOM from a groundwater on five powdered activated carbons (PACs) with widely different PSDs. The capacity for NOM correlated best with the surface area of pores in the diameter range of 15-50 A, although some NOM also adsorbed in the smaller pores as evidenced by a reduction in capacity for atrazine when NOM was present. Kinetic tests for atrazine on PACs with various levels of preadsorbed NOM showed that the magnitude of the pore blockage effect by NOM was lower for PACs with higher surface area of pores with diameter in the range of 15-50 A. Therefore increasing pores in the size range where NOM adsorb can reduce the extent of the pore blockage competitive effect on the target compound atrazine. The effect of PSD was further studied with a flow-through PAC-membrane hybrid watertreatment system, in which experimental results successfully verified model simulations by the COMPSORB model.

The Use of Liquid Phase Adsorption Isotherms for Characterization of Activated Carbons

The characterization of three commercial activated carbons was carried out using the adsorption of various compounds in the aqueous phase. For this purpose the generalized adsorption isotherm was employed, and a modification of the Dubinin–Radushkevich pore filling model, incorporating repulsive contributions to the pore potential as well as bulk liquid phase nonideality, was used as the local isotherm. Eight different flavor compounds were used as adsorbates, and the isotherms were jointly fitted to yield a common pore size distribution for each carbon. The bulk liquid phase nonideality was incorporated through the UNIFAC activity coefficient model, and the repulsive contribution to the pore potential was incorporated through the Steele 10-4-3 potential model. The mean micropore network coordination number for each carbon was also determined from the fitted saturation capacity based on percolation theory. Good agreement between the model and the experimental data was observed. In addition, excellent agreement between the bimodal gamma pore size distribution and density functional theory-cum-regularization-based pore size distribution obtained by argon adsorption was also observed, supporting the validity of the model. The results show that liquid phase adsorption, using adsorptive molecules of different sizes, can be an effective means of characterizing the pore size distribution as well as connectivity. Alternately, if the carbon pore size distribution is independently known, the method can be used to “measure” critical molecular sizes.

The Change of Pore Structure of Various Hard Carbons by Heat Treatment

The BET surface area and pore size distribution were determined by physical adsorption-desorption measurement of carbon dioxide at 195K on various hard carbons, prepared from divinyl benzene polymer (DVBP), copolymer of divinyl benzene and acrylic acid (IRC-50), phenol-formal-dehyde resin (P-F) and carbon fiber (C-F), and change of pore structure in carbons with heat treatment temperature (HTT) was discussed.Each carbon was heat treated at various temperatures between 1173-2273K (900-2000°C)Below the heat treatment temperature of 1473K, the isotherms for all carbons were those of Langmuir-type.Above 1673K, however, the isotherms were BET-II-type, except the carbon fiber. The surface area of IRC-50 and C-F carbons decreased from relatively large value (ca.300m2/g) below 1473K to small value, less than 100m2/g, above 1673K.On the DVBP carbon, however, rather large area, few hundreds square meters per gram, was maintained over the temperature range examined. The area of P-F carbon was 31.5m2/g at 1273K, increased to 59.7 at 1773K and then decreased to 27.5m2/g at 2273K.The pores in these carbons were micro pores and transitional pores.In the carbons with HTT of 1473K, almost all of pores had the diameter less than about 30 A.With the increase in HTT, the maximum of the pore diameter shifted to larger side.The temperature programmed desorption (TPD) method was proved to be a promising way to show an outline of the pore size distribution in carbons.