Mesoporous Carbon Xerogel Research Articles

Adsorption of Reactive Blue 13 from Dyeing Wastewater onto Mesoporous Carbon Xerogels

Adsorption of Reactive Blue 13 from Dyeing Wastewater onto Mesoporous Carbon Xerogels

Copper-Doped Tin Oxides Supported on Mesoporous Carbon Xerogel for Boosting the Electrochemical Reduction of CO2 to Formate in Bicarbonate Solution Coupled with CO2

Copper-Doped Tin Oxides Supported on Mesoporous Carbon Xerogel for Boosting the Electrochemical Reduction of CO₂ to Formate in Bicarbonate Solution Coupled with CO₂

Mesoporous carbon xerogel as a promising adsorbent for capture and storage of liquified natural gas vapors

Mesoporous carbon xerogel as a promising adsorbent for capture and storage of liquified natural gas vapors

Integrated Adsorption–Photodegradation of Organic Pollutants by Carbon Xerogel/Titania Composites

Recent studies on the removal of pollutants via adsorption include the use of carbon-based adsorbents, due to their high porosity and large surface area; however, such materials lack photoactive properties. This study evaluates the synergistic effect of integrated mesoporous carbon xerogel (derived from resorcinol formaldehyde) and titanium dioxide (TiO2) for combined adsorption and photodegradation application. The complex formed between carbon xerogel and TiO2 phase was investigated through FTIR, proving the presence of a Ti-O-C chemical linkage. The physicochemical properties of the synthesised adsorbent-photocatalyst were probed using FESEM, BET analysis and UV-Vis analysis. The kinetics, equilibrium adsorption, effect of pH, and effect of adsorbent dosage were investigated. The expansion of the absorbance range to the visible range was verified, and the corresponding band gap evaluated. These properties enabled a visible light response when the system was exposed to visible light post adsorption. Hence, an assistive adsorption-photodegradation phenomenon was successfully executed. The adsorption performance exhibited 85% dye degradation which improved to 99% following photodegradation. Further experiments showed the reduction of microorganisms under visible light, where no microbial colonies were observed after treatment, indicating the potential application of these composite materials.

(Digital Presentation) Synergistic Effect of Sn and Cu Oxides for the Electrochemical Reduction of CO2 to Formic Acid

The development of an electrochemical catalyst system that converts carbon dioxide (CO2) to high-value chemicals, such as formic acid (FA) will simultaneously curb CO2 emissions to atmosphere and provide sustainable pathways to create a range of fuels at lower cost. Electrochemical conversion of CO2 to FA is a two-electron reduction process and can be carried out at ambient conditions, and the reduced product has been found wide-ranging applications in chemical industries for production of household products, and a safe liquid-phase chemical for hydrogen storage. Synergistic bimetallic electrocatalysts can improve the activity and selectivity over their monometallic counterparts by tuning the structure, morphology, and composition. At the University of Kentucky’s Institute for Decarbonization and Energy Advancement (UK IDEA), our enhanced bimetallic oxide carbon utilization (EBOCU) process uses an engineered catalyst that facilitates operating at relatively low applied potentials, and high product selectivity to produce FA. Using bimetallic tin-copper oxide containing 95 mol% of Sn and 5 mol% of Cu immobilized on mesoporous carbon xerogel and alkaline electrolyte, we observed that hydrogen evolution reaction is suppressed and the selectivity towards formate is enhanced for the cell potential from 3.6 V through 4.0 V. Notably, our electrochemical reactor is successful in converting CO2 to formate at the rate of 2 mM/h in 3 mL/min flow system. Maximum faradaic efficiency of 94% is achieved towards formate at 3.8 V, which remained above 80% even after 200 h of continuous operation.

Mesoporous Carbon Xerogels Adsorbents for Adsorption of Cadmium and p-Nitrophenol Pollutants: Kinetic and Equilibrium Studies

Mesoporous carbon xerogels were prepared by carbonization of resorcinol-formaldehyde xerogel in presence of tannic acid as a soft-template at 700oC for 30, 60 and 90 min, respectively. Morphology, textural, surface functional surface groups and thermal analyses were measured. Their efficiency in liquid-adsorption of cadmium ions and PNP in a batch mode was carried out. Effect of some key factors such as pH, carbon dose, and contact time of cadmium ions and PNP as well as kinetic adsorption studies were performed. It was found that the obtained carbon xerogels of mesoporous structure have a moderate total surface area reached to 268 m2/g with various surface functional groups are effective sites for adsorbing cadmium ions and PNP from aqueous solutions. The adsorption behavior of both adsorbates on the prepared carbon samples was best described by the pseudo-second-order kinetic and Langmuir adsorption models. The maximum adsorption capacities of cadmium ions and PNP were 99 and 133 mg/g, respectively; onto the prepared carbon xerogel at 700oC and 60 min. As a result of these observations, the produced mesoporous carbon samples are very effective adsorbents for extracting considerable amounts of cadmium ions and PNP from aqueous solutions.

Synthesis of Mesoporous Carbon Xerogel and Activation by Oxidative Treatment

Synthesis of carbon xerogel and modification of its surface by various oxidative treatments are explored. Organic gel was synthesized by following the conventional sol-gel approach using formaldehyde and resorcinol. The wet gel was dried under subcritical condition and then carbonized, leading to carbon xerogel. Subsequently, the carbon xerogel was subjected to surface activation by means of oxidative treatment with nitric acid, sulphuric acid as well as aerial oxidation. Surface acid/base properties of the carbon xerogel have been strongly altered by treatments with nitric acid as well as with sulphuric acid. On the other hand, total surface area and pore volume have been significantly modified by air activation.

Mesoporous carbon xerogel material for the adsorption of model naphthenic acids: structure effect and kinetics modelling

ABSTRACT The study examined the preparation, characterization and the use of carbon xerogel (CX) material for the adsorption of three model naphthenic acids (NAs); such as, heptanoic acid (HPA), 5-cyclohexanepentanoic acid (CHPA), and 5-phenylvaleric acid (PVA). CX was synthesized by sol–gel method from resorcinol and formaldehyde. The characterization results showed that CX was a mesoporous material with large surface area (573 m2/g) and high pore volume (1.55 cm3/g), which was mainly composed of carbon (93.20%) and oxygen (6.71%). Adsorption studies revealed that PVA, the NA having an aromatic ring was adsorbed more easily by CX (87 mg/g) due to π–π interactions, followed by HPA (65 mg/g) and CHPA (61 mg/g). In addition, by studying the effect of solution pH, the result confirmed that repulsion greatly hindered the adsorption of HPA onto CX at pHs above that of the pHPZC and at lower pHs attractive electrostatic forces promoted adsorption. Adsorption kinetics fitted the pseudo-first-order model, which suggested that physisorption was most likely the means of adsorption. For the intraparticle diffusion model, the rate of film diffusion was higher than the rate of pore diffusion for each model compound regardless of their structure. Accordingly, this confirmed that pore diffusion was the rate-limiting step, although film diffusion still maintained a significant role in the rate of diffusion. In general, CX exhibited excellent adsorption performance due to its highly mesoporous character so it could be used as a passive treatment method in tailing ponds for removal of organic matters.

Surface influence on the rotational and translational dynamics of molecules confined inside a mesoporous carbon xerogel.

Low-field nuclear magnetic resonance techniques are employed to extract information about the effects introduced by the interaction with the surface on the rotational and translational dynamics of molecules confined inside a mesoporous carbon xerogel. The molecules under study were water, cyclohexane, and hexane. They were chosen due to their different interaction strength with the carbonaceous matrix. Frequency dependent longitudinal relaxation measurements, using the fast field cycling technique, allowed extraction of the fractal dimension of the carbon xerogel surface. It was observed that the measured value is influenced by the molecule affinity to the surface. Diffusion measurements, using the pulse field gradient technique, have revealed that the stronger interaction with the surface of cyclohexane and hexane molecules leads to an increased diffusive tortuosity, as compared with water.

Change of self-discharge mechanism as a fast tool for estimating long-term stability of ionic liquid based supercapacitors

A systematic study is presented on self-discharge (SD) characteristics and leakage current levels of supercapacitors based on various carbon materials in ionic liquids: 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMImTFSI) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF4). The higher SD rate occurring with partly mesoporous carbon xerogels, opposed to microporous activated carbon, suggests underlying faradaic induced processes rather than SD governed by charge redistribution. The passivation of some surface active sites of carbon xerogels by high-temperature di-hydrogen treatment resulted in reduced SD extent. The cell potential hold dependence of SD was studied for individual electrodes, showing changes of SD mechanism in EMImTFSI for both electrode polarities at cell potential higher than 2.8 V, against ∼3.4 V and >3.6 V for the negatively and positively charged electrodes in BMImBF4.A good correlation was established between the electrochemical stability limits determined by long-lasting floating tests and the limits suggested by changes in the SD mechanism and increase in measured leakage current. Hence, SD and leakage current analysis is a sensitive and much faster tool for determining the maximum cell potential applicable to supercapacitors than life time tests by floating, and should be more extensively applied in the future for such objective.

Low-Pressure Plasma Synthesis of Ni/C Nanocatalysts from Solid Precursors: Influence of the Plasma Chemistry on the Morphology and Chemical State

Nanocatalyst materials based on metal nanoparticles (NPs) deposited on mesoporous carbon substrates are widely used in catalysis and energy storage; however, conventional wet-chemical deposition methods based on the reduction of metal salts are not always the best choice when looking for a process ensuring easy scalability and low environmental impact. Moreover, additional surface functionalization steps, such as the addition of nitrogen- or oxygen-containing groups, are more and more explored to increase the activity or the chemical stability of catalysts. In this work, we investigate a new methodology for the fabrication of nickel/carbon nanocatalysts relying on a low-pressure radio frequency plasma treatment of solid (powder) precursors. A mesoporous carbon xerogel is used as support for nickel NPs synthesized through the decomposition of an organometallic nickel precursor in a plasma discharge. Different plasma treatment conditions and chemical environments are applied by varying the plasma power and ...

Probing into the mesoporous structure of carbon xerogels via the low-field NMR relaxometry of water and cyclohexane molecules

The liquid morphology of water and cyclohexane molecules, under partially saturated conditions inside the porous structure of two mesoporous carbon xerogels, was investigated using low-field nuclear magnetic resonance (NMR) relaxometry. The two xerogels were prepared under the same conditions, but with a different resorcinol-to-catalyst ratio. Two techniques were used in our investigations: the well-known Carr–Purcell–Meiboom–Gill (CPMG) pulse sequence for transverse relaxation measurements and the Fast Field-Cycling (FFC) relaxometry technique for longitudinal relaxation dispersion measurements. It was found a stronger interaction of cyclohexane molecules with the pore surface as compared with water molecules. This leads to a uniform coverage of cyclohexane molecules on the pore surface for lower filling degrees while, in the case of water filled carbon xerogels, the distribution was non-uniform. Due to the stronger adsorption of cyclohexane molecules on the pore surface, it was possible to identify the micropores of the carbon xerogels predicted by nitrogen adsorption data. The NMR relaxation data have clearly demonstrated that, by increasing the resorcinol-to-catalyst ratio, the size of mesopores increases. Moreover, the enhanced adsorption affinity of carbon xerogels for cyclohexane shows that this type of materials can be employed as adsorbents for the removal of similar organic contaminants from water.

Influence of Synthesis Variables on the Textural Properties of Mesoporous Carbon Xerogels

Influence of synthesis variables on the textural properties of mesoporous carbon xerogels is studied. Variables explored in synthesizing mesoporous carbon xerogels (CX) are: (i) initial formaldehyde/resorcinol molar ratio in preparing the sol, (ii) pH of sol-gel processing, (iii) temperature of gelling and subsequent curing of the gel, and (iv) mode of subcritical drying of the wet gel. Making of sol having formaldehyde/resorcinol molar ratio little higher than 2 and sol-gel processing at pH around 6 resulted in carbon xerogel with wide pores. Curing of gel at higher temperature resulted in carbon xerogel with narrower pores. Drying of the organic gel after exchanging water with low boiling organic solvent was highly beneficial in obtaining carbon xerogel with wider pores along with larger mesoporous area.

Polyvinyl Pyrrolidone Wrapped Sn Nanoparticles/Carbon Xerogel Composite as Anode Material for High Performance Lithium Ion Batteries

To effectively alleviate the severe volume expansion, pulverization and aggregation of anodes during the charge and discharge processes, we designed novel three-dimensional porous Sn@PVP-CX composites as anodes for lithium ion batteries (LIBs), in which Sn nanoparticles (NPs) are wrapped with outer layer of polyvinyl pyrrolidone (PVP), and the Sn@PVP core-shell nanostructures are homogenously loaded on mesoporous carbon xerogel (CX) matrix. Introducing a flexible and stable layer of PVP on surface of Sn NPs can effectively prevent the aggregation of Sn NPs and counteract the pulverization of Sn NPs due to the large volume changes generated during the lithiation-delithiation processes. CX acted as a conductive matrix, displaying porous structure with merits of continuous porosity, interconnected 3D porous structure and large interfacial surface area, can effectively alleviate the strain and stress from volume changes, provide the sufficient channel for Li ions and electrons, shorten the diffusion path of Li ions. The unique Sn@PVP-CX with Sn@PVP NPs homogenously loaded on the CX matrix can show improved structure stability as LIBs anodes. The LIBs based on Sn@PVP-CX composite anode display greatly improved electrochemical performance, showing a capacity of 757mA h g−1 at a current density of 100mAg−1 after 100 cycles, improved cycling stability and rate capability. The related mechanism is investigated.

Graphitic mesoporous carbon xerogel as an effective catalyst support for oxygen reduction reaction

Graphitic mesoporous carbon xerogel (GMCX) with high surface area and comparable mesoporous structure is prepared via a sol–gel process with cobalt acetate, followed by the subsequent pyrolysis in nitrogen flow at 1800 °C. 20 wt.% Pt/GMCX catalyst is synthesized using the as-prepared GMCX powder as support. The results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) characterizations for Pt/GMCX indicate that Pt nanoparticles dispersed on GMCX have a much smaller average nanoparticle size and narrower size distribution than Pt nanoparticles grown on commercial XC-72 carbon black and GCX powder which we reported before. The results of linear sweep voltammetry (LSV) test demonstrate that the Pt/GMCX catalyst exhibits a higher oxygen reduction reaction (ORR) electrocatalytic activity than commercial Pt/C and Pt/GCX. The corrosion resistance of the catalysts was evaluated by potential cycling accelerated aging test (AAT). Pt/GMCX catalyst exhibits very nearly the same Pt electrochemical active surface area (EASA) retention as Pt/GCX (53.3% for Pt/GMCX and 53.0% for Pt/GCX), which is higher than that of commercial Pt/C (39.2%). Combined with its facile synthesis process, GMCX powder is a promising substitute for commercial Pt electrocatalyst support in achieving high catalytic activity and good durability for ORR.

Sulfurized carbon xerogels as Pt support with enhanced activity for fuel cell applications

Carbon xerogels represent nowadays an outstanding alternative to carbon blacks for the preparation of efficient fuel cell electrocatalysts, due to their easily tunable and well developed mesoporous structure. To further improve both activity and durability of Pt/C catalysts, the introduction of heteroatoms (such as O, N, S, P, B, etc.) in the structure of carbon materials has been proposed. In the present work, highly mesoporous carbon xerogels (CXGs) have been subjected to a sulfurization process with elemental sulfur. The insertion of S into the carbon matrix does not compromise their mesoporous structure. Pt catalysts supported on sulfurized carbon xerogels show enhanced catalytic activity towards both the methanol electro-oxidation and the oxygen electro-reduction reactions, exceeding not only the performance of the catalyst supported on the bare xerogel, but also of the catalyst supported on a commercial carbon black. The sulfurization treatment is also effective in improving the resistance of Pt/CXG catalysts towards corrosion phenomena occurring at the fuel cell cathode.

Advanced and economical ambient drying method for controlled mesopore polybenzoxazine-based carbon xerogels: Effects of non-ionic and cationic surfactant on porous structure

Polybenzoxazine has been successfully synthesized by a facile quasi-solventless method and used as a precursor for producing carbon xerogels via an ambient drying method, rather than usually used CO2 critical or freeze drying. In this work, we aim to study the effect of non-ionic (Synperonic NP30) and cationic (CTAB) surfactants on porous structure of polybenzoxazine-based carbon xerogels. Of particular interest is the formation of inter-connected structure of mesoporous carbon xerogels with mesopore diameters in the range of 15–36nm by using different concentrations of the cationic surfactant. In addition, carbon xerogel nanospheres with the size of 50–200nm are also obtained through the emulsion process. The mesopore diameters start to decrease when the carbon xerogel nanospheres are formed at the cationic surfactant concentration of equal to or exceeding 0.030M. By using the non-ionic surfactant, the properties of the obtained carbon xerogels are shifted from mesoporous materials for the reference carbon xerogel (no surfactant added) to microporous materials at higher concentrations of the non-ionic surfactant (0.009–0.180M). The carbon xerogel microspheres with the diameter size of about 2.5μm are also obtained through the emulsion process when the concentration of the non-ionic surfactant is at 0.180M.

Gas Diffusion Electrodes for Li/O2 Batteries: Impact of Porosity, Wettabiliy and Electrode Design

Beyond lithium ion batteries the metal air technology is considered to be very promising for various energy storage applications in a long-term view. Due to its very high theoretical energy density the aprotic Li/O2 system in particular has attracted broad attention during the recent years. Here molecular oxygen O2 is reduced at a gas diffusion electrode (GDE) upon discharge forming Li2O2 as a solid discharge product which precipitates within the electrode to be reoxidized under the release of oxygen upon recharge. The performance of a Li/O2cell is therefore critically influenced by the structural properties of the used GDE. Based on carbon, especially the porosity, the wetting behavior and the general design of the GDE has a huge impact on the capacity and efficiency of the cell. Regarding the wettability of a GDE, a thin electrolyte film within the inner pore structure is considered to be ideal to provide efficient oxygen transport through open gas channels as well as improved diffusion properties towards the active surface. Using mesoporous carbon xerogels which exhibit defined open pore structures, large inner surfaces and pore volumes we were able to investigate the pore wettability with different solvents by using 1H relaxation MRT techniques. To investigate them as active material in the Li/O2 system they were synthesized directly into a woven carbon paper to create ready-to-use electrodes without any binder. Here, the discharge reaction was studied by electrical impedance spectroscopy (EIS) using 1M LiTFSI/DMSO as electrolyte and Li metal as reference electrode in a three electrode setup. A model for the interpretation of the limiting factors regarding the GDE performance due to the formation and deposition of the discharge product could be developed. For further investigation of these factors the chemical and morphological characterization of the discharge products in dependence on the GDE design was addressed by XPS analyses. Besides looking at the electrolyte facing side the deposition of discharge product in the bulk of the active layer in the GDE and at the oxygen facing side were investigated. For information about the bulk of the GDE cross-section measurements as well as depth profiling by argon ion sputtering were conducted.

Bismuth doped carbon xerogel nanocomposite incorporated in chitosan matrix for ultrasensitive voltammetric detection of Pb(II) and Cd(II)

A new modified electrode based on a modified electrode incorporating Bi doped mesoporous carbon xerogel (Bi–CX), confined in a chitosan matrix (Chi) and deposited on a glassy carbon (GC), was elaborated and investigated for Pb(II) and Cd(II) voltammetric trace detection. Bi–CX was prepared by sol–gel method, coupled with drying under ambient conditions and followed by thermal pyrolysis. The morpho-structural characteristics of the new nano-material material such as specific surface area, pore size distribution, pore volume, phase composition and crystallite mean size were examined by using from N2 adsorption/desorption isotherms, TEM, SEM and XRD measurements. The electrochemical behavior of the GC/Chi–(Bi–CX) modified electrode as well as its relevance for Pb(II) and Cd(II) trace detection were investigated by cyclic voltammetry and square wave anodic stripping voltammetry. The linear range, sensitivity, and detection limit of the new sensor were estimated as (0.2–2)ppb, 5.6A/ppm and 0.07ppb, for Pb(II), and (11.2–124)ppm, 22.7nA/ppm and 5.06ppm, for Cd(II), respectively. The excellent analytical parameters for Pb(II) detection were exploited for the determination of the Pb(II) concentration in drilled well water samples. The results were found in good agreement with those obtained by atomic absorption spectrophotometry.

Influence of the Synthesis Method for Pt Catalysts Supported on Highly Mesoporous Carbon Xerogel and Vulcan Carbon Black on the Electro-Oxidation of Methanol

Platinum catalysts supported on carbon xerogel and carbon black (Vulcan) were synthesized with the aim of investigating the influence of the characteristics of the support on the electrochemical performance of the catalysts. Three synthesis methods were compared: an impregnation method with two different reducing agents, sodium borohydride and formic acid, and a microemulsion method, in order to study the effect of the synthesis method on the physico-chemical properties of the catalysts. X-ray diffraction and transmission electron microscopy were applied. Cyclic voltammetry and chronoamperometry were used for studying carbon monoxide and methanol oxidation. Catalysts supported on carbon xerogel presented higher catalytic activities towards CO and CH3OH oxidation than catalysts supported on Vulcan. The higher mesoporosity of carbon xerogel was responsible for the favored diffusion of reagents towards catalytic centers.