Phosphoric acid activation—Functionalization and porosity modification

4,4′-Bis(maleimidodiphenyl) methane (BM) and divinylbenzene (DVB) copolymers with different compositions were used for production of carbons by carbonization and phosphoric acid activation. It has been shown that both BM and DVB polymers are good carbon precursors which show the same potential to produce carbonaceous material. However, despite cross-linked nature of all polymers, BM softens before formation of coke giving non-porous material. Phosphoric acid activation of polymer precursor increased the yield, surface area and pore volume as compared to acid-free heat treatment. Phosphoric acid activation of polymer precursor resulted in carbon material containing 6-8% of phosphorus and considerable amount of surface acidic groups of four types (total 2.6-3.2 mmol/g) which are responsible for metal ion adsorption from aqueous solutions.     

Ammoxidation of carbon materials for CO2 capture

Ammoxidised carbons were produced from three different starting materials: an activated carbon obtained from wood by chemical activation using the phosphoric acid process, a steam activated peat-based carbon, and a char obtained from a low-cost biomass feedstock, olive stones. Nitrogen was successfully incorporated into the carbon matrix of the different materials, the amount of nitrogen uptake being proportional to the oxygen content of the precursor. At room temperature the CO₂ capture capacity of the samples was found to be related to the narrow micropore volume, while at 100 °C other factors such as surface basicity took on more relevance. At 100 °C all the ammoxidised samples presented an enhancement in CO₂ uptake compared to the parent carbons.     

Photolysis of light-transforming polymer materials on the basis of europium(III) nitrate with 1,10-phenanthroline and anthranilic acid

Light-transforming polymer materials on the basis of europium(III) nitrate with 1,10-phenanthroline and anthranilic acid, having an intense luminescence in the 400–650 nm spectral range, were obtained. It is shown that the photostability of the polymer materials on the basis of the obtained compositions is higher than of polymer materials activated by europium(III) compounds. Luminescent and photochemical characteristics of the obtained polymer compositions are determined by the molar ratio of the dopants: the maximum luminescence intensity and photostability is characteristic for the polymeric material containing europium(III) nitrate with 1,10-phenanthroline and anthranilic acid at a molar ratio of 1: 2.     

The influence of oxidation with nitric acid on the preparation and properties of active carbon enriched in nitrogen

The effect of oxidation by 20% nitric acid on the properties and performance of active carbons enriched with nitrogen by means of the reaction with urea in the presence of air has been studied. The study has been made on demineralised orthocoking coal and the carbonisates obtained from it at 600 or 700 °C, subjected to the processes of nitrogenation, oxidation and activation with KOH in different sequences. The amount of nitrogen introduced into the carbon with the aid of urea has been found to depend on the stage at which the process of nitrogenation was performed. The process of oxidation of the demineralised coal and the active carbon obtained from the former has been found to favour nitrogen introduction into the carbon structure. In the process of nitrogenation of the carbonisates the amount of nitrogen introduced has inversely depended on the temperature of carbonisation. The modifications of the processes permitted obtaining materials of different textural parameters, different acid-base character of the surface and different iodine sorption capacity.     

Characterization of PSD of activated carbons by using slit and triangular pore geometries

A mixed geometry model for activated carbons, representing the porous space as a collection of an undetermined proportion of slit and triangular pores, is developed, evaluated theoretically and applied to the characterization of a controlled series of samples of activated carbon obtained from the same precursor material. A method is proposed for the determination of the Pore Size Distribution (PSD) for such a mixed geometry model, leading to the unique determination of the proportion of pores of the two geometries fitting adsorption data. By using the Grand Canonical Monte Carlo (GCMC) simulation method in the continuum space, families of N2 adsorption isotherms are generated both for slit and triangular geometry corresponding to different pore sizes. The problem of the uniqueness in the determination of the PSD by fitting an adsorption isotherm using the mixed geometry model is then discussed and the effects of the addition of triangular pores on the PSD are analyzed by performing a test where the adsorption isotherm corresponding to the known PSD is generated and used as the “experimental” isotherm. It is found that a pure slit geometry model would widen the PSD and shift it to smaller sizes, whereas a pure triangular geometry model would produce the opposite effect. The slit and triangular geometry families of isotherms are finally used to the fit experimental N₂ adsorption data corresponding to a family of activated carbons obtained from coconut shells through a one-step chemical activation process with phosphoric acid in air, allowing for the determination of the micropore volume, the proportion of slit and triangular pores and the PSD corresponding to the mixed geometry. The same experimental data were fit using both the conventional slit pore model and the mixed geometry model. From the analysis of the effect of different preparation procedures on the resulting PSDs, it is concluded that the proposed mixed geometry model may probably better capture the morphology and energetics of activated carbons prepared by chemical activation under mild temperatures.     

Preparation and characterization of porous DVB copolymers and their applicability for adsorption (solid-phase extraction) of phenol compounds

Using DVB, three new porous copolymers in the form of microspheres were prepared, characterized and used as adsorbents for phenol and its chlorinated derivatives. As the monomers: 4,4′-bis(maleimidodiphenyl)methane (BM), 2,3-bis(2-hydroxy-3-methylacryloyloxy-propoxy)naphthalene (2,3-NAF) and 2,3-epoxypropyl methacrylate (GLY) were used. All the studied materials were synthesized under the same conditions by means of suspension copolymerization. The DVB copolymers were characterized by elemental analysis, FTIR spectroscopy, TG and DSC analyses and N₂ sorption. The off-line solid-phase extraction method (SPE) was used to estimate sorption properties of the copolymers. The results show that the newly obtained materials are mesoporous but their shape of pores and chemical structures are different. BM-DVB and GLY-DVB are characterized by slit-shaped pores and wide pore size distribution. 2,3-NAF-DVB also possesses slit pores but distribution of pore size is narrower. Of those studied BM-DVB is the most interesting material. It has good sorption properties and heat resistance.     

Preparation and characterization of activated carbon produced from pomegranate seeds by ZnCl2 activation

In this study, pomegranate seeds, a by-product of fruit juice industry, were used as precursor for the preparation of activated carbon by chemical activation with ZnCl₂. The influence of process variables such as the carbonization temperature and the impregnation ratio on textural and chemical-surface properties of the activated carbons was studied. When using the 2.0 impregnation ratio at the carbonization temperature of 600 °C, the specific surface area of the resultant carbon is as high as 978.8 m² g⁻¹. The results showed that the surface area and total pore volume of the activated carbons at the lowest impregnation ratio and the carbonization temperature were achieved as high as 709.4 m² g⁻¹ and 0.329 cm³ g⁻¹. The surface area was strongly influenced by the impregnation ratio of activation reagent and the subsequent carbonization temperature.     

p-Chlorophenol adsorption on activated carbons with basic surface properties

The adsorption of p-chlorophenol (PCP) from aqueous solution on activated carbons (ACs) with basic surface properties has been studied. The ACs were prepared by two methods. The first method was based on the modification of a commercial CWZ AC by high temperature treatment in an atmosphere of ammonia, nitrogen and hydrogen. The second approach comprised the carbonization followed by activation of N-enriched polymers and coal tar pitch using CO₂ and steam as activation agent. The resultant ACs were characterized in terms of porous structure, elemental composition and surface chemistry (pH_PZC, acid/base titration, XPS). The adsorption of PCP was carried out from an aqueous solution in static conditions. Equilibrium adsorption isotherm was of L2 type for polymer-based ACs, whereas L3-type isotherm was observed for CWZ ACs series. The Langmuir monolayer adsorption capacity was related to the porous structure and the amount of basic sites. A good correlation was found between the adsorption capacity and the volume of micropores with a width < 1.4 nm for polymer-based ACs. Higher nitrogen content, including that in basic form, did not correspond to the enhanced adsorption of PCP from aqueous solution. The competitive effect of water molecule adsorption on the PCP uptake is discussed.     

Photolysis of light-transforming polymeric materials based on europium(III) nitrate with 1,10-phenanthroline and quinaldic acid

Light-transforming polymeric materials based on two luminophor dopants (europium(III) nitrate with 1,10-phenanthroline and quinaldic acid characterized by intense luminescence in the spectral range of 400–650 nm) have been fabricated. It has been established that the photoresistance of polymeric materials based on the fabricated composites is higher than that of the polymeric material activated with europium(III) nitrate with 1,10-phenanthroline. It has been also established that luminescence and photochemical characteristics of polymeric composites are determined by the dopant molar ratio: the maximum luminescence intensity and photoresistance characterize the polymeric material containing europium(III) nitrate with 1,10-phenathroline and quinaldic acid at a molar ratio of 1: 2.     

Preparation of activated carbon from cherry stones by chemical activation with ZnCl2

Cherry stones (CS), an industrial product generated abundantly in the Valle del Jerte (Cáceres province, Spain), were used as precursor in the preparation of activated carbon by chemical activation with ZnCl₂. The influence of process variables such as the carbonisation temperature and the ZnCl₂:CS ratio (impregnation ratio) on textural and chemical-surface properties of the products obtained was studied. Such products were characterised texturally by adsorption of N₂ at −196 °C, mercury porosimetry and density measurements. Information on the surface functional groups and structures of the carbons was provided by FT-IR spectroscopy. Activated carbon with a high development of surface area and porosity is prepared. When using the 4:1 impregnation ratio, the specific surface area (BET) of the resultant carbon is as high as 1971 m² g⁻¹. The effect of the increase in the impregnation ratio on the porous structure of activated carbon is stronger than that of the rise in the carbonisation temperature, whereas the opposite applies to the effect on the surface functional groups and structures.     

The atomic scale structure of saccharose-based carbons

Abstract

Activated carbons (ACs) have a wide range of applications, in which the largely expanded specific surface plays a major role. The question of their structure came back to the limelight with the discovery of nanotubes fullerenes, which suggested that curved surfaces may be present in their structure and which incorporates well into the ideas of ACs porous structure. The source of those curved surfaces is atomic defects present inside the in-plane graphitic honeycomb lattice. Such defects have a crucial influence on the macroscopic morphology as well as physical properties of the material. The activated carbon (AC) in this work was derived from carbonised saccharose by activation with NaOH. Both materials – before and after activation were investigated. The main methods used in this study are wide angle neutron scattering and wide angle X-ray scattering combined with computer simulations. Confirmation of the proposed structures was sought with high-resolution transmission electron microscopy and Raman scattering. In this case, the use of classical crystallography to interpret experimental data was impossible due to the lack of periodic three-dimensional symmetry. Due to this fact, the data was analysed both in real and reciprocal space in the form of a pair correlation function and a structure factor. The experimental data were compared with calculated atomistic models. As a validation, the discrepancy factor between the theoretically and experimentally obtained functions was used. The presented innovative approach can be applied to different carbon materials with varying degrees of disorder.     

Nanostructured carbons for solid phase extraction

Nanostructured carbons have been obtained by the template method using zeolite NaY and silica gels (SG60, Fluka and ZK, POCh) as structure directing agents. Texture and porous structure of carbons were characterized by TEM, XRD and nitrogen adsorption. Surface chemistry was investigated by the potentiometric titration method. It has been shown that all carbons show developed and uniform porous structure with mean size in the micropore range (1.1 nm) for zeolite derived carbon and in the mesopore range (3.4 and 4.8 nm) for silica gel derived carbons. The BET surface area of silica gel derived carbons is in the range 1230-1280 m²/g whereas zeolite derived carbon possesses very high BET surface area, 3000 m²/g. Potentiometric titration showed that carbons obtained by the template method contain significant amount of acid surface groups (carboxylic, lactone/enol and phenolic) with the total amount 1.1-1.5 mmol/g. To study adsorption-desorption properties of nanostructured carbons towards phenol and chlorophenols the solid phase extraction method was used. High recoveries of chlorophenols were obtained (80-93%) at the breakthrough volumes 1700-3000 mL. The recoveries are much higher than that obtained with commercially available carbon ACC (Supelco).     

Characterization of synthetic carbons activated with phosphoric acid

The structural heterogeneity of synthetic phosphoric acid activated carbons has been analyzed using pore-size distributions (PSDs) obtained from nitrogen at −196 °C and carbon dioxide at 0 °C isotherms. PSDs where obtained by the BET–Kelvin method. It is shown that the BET–Kelvin method is in good agreement with DFT and provides a fast means for assessment of the porous structure of adsorbents. PSDs obtained by the BET–Kelvin method using different adsorbates give results consistent with each other. Due to the restricted pressure range for carbon dioxide adsorption isotherm the PSD gives information only about pores in the micropore range. The agreement between different methods is better for small micropores.     

Fabrication of three-dimensional electrical patterns by swollen-off process: An evolution of the lift-off process

We present a novel process to fabricate three-dimensional (3D) metallic patterns from 3D printed polymeric structures utilizing different hygroscopic swelling behavior of two different polymeric materials. 3D patterns are printed with two different polymers as cube shape. The surface of the 3D printed polymeric structures is plated with nickel by an electroless plating method. The nickel patterns on the surface of the 3D printed cube shape structure are formed by removing sacrificial layers using the difference in the rate of hygroscopic swelling between two printing polymer materials. The hygroscopic behavior on the interfaced structure was modeled with COMSOL Multiphysics. The surface and electrical properties of the fabricated three-dimensional patterns were analyzed and characterized.     

Cauliflower-derived porous carbon without activation for electrochemical capacitor and CO<Subscript>2</Subscript> capture applications

Carbon materials have attracted great attention in CO₂ capture and energy storage due to their excellent characteristics such as tunable pore structure, modulated surface properties and superior bulk conductivities, etc. Biomass, provided by nature with non-toxic, widespread, abundant, and sustainable advantages, is considered to be a very promising precursor of carbons for the view of economic, environmental, and societal issues. However, the preparation of high-performance biomass-derived carbons is still a big challenge because of the multistep process for their synthesis and subsequent activation. Herein, hierarchically porous structured carbon materials have been prepared by directly carbonizing dried cauliflowers without any addition of agents and activation process, featuring with large specific surface area, hierarchically porous structure and improved pore volume, as well as suitable nitrogen content. Being used as a solid-state CO₂ adsorbent, the obtained product exhibited a high CO₂ adsorption capacity of 3.1 mmol g^?1 under 1 bar and 25 °C and a remarkable reusability of 96.7% retention after 20 adsorption/regeneration cycles. Our study reveals that choosing a good biomass source was significant as the unique structure of precursor endows the carbonized product with abundant pores without the need of any post-treatment. Used as an electrode material in electrochemical capacitor, the non-activated porous carbon displayed a fairly high specific capacitance of 228.9 F g^?1 at 0.5 A g^?1 and an outstanding stability of 99.2% retention after 5000 cycles at 5 A g^?1.

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Graphical abstract Hierarchically porous structured carbon materials are prepared by directly carbonizing dried cauliflower without any agents and process of activation for high performance of CO₂ capture and capacitor.

     

Adsorption and structural properties of soft-templated mesoporous carbons obtained by carbonization at different temperatures and KOH activation

Two series of phenolic resin-based mesoporous carbons were prepared by soft-templating strategy, which involves the formation of thermosetting carbon precursor by polymerization of phloroglucinol and formaldehyde in hydrophilic mesodomains of a thermally decomposable triblock copolymer used as a soft-template. It was shown that the volumes of mesopores and micropores in the resulting carbons can be tuned by varying carbonization temperature of phenolic resins in the range from 400 to 1000 °C followed by the post-synthesis KOH activation at 700 °C. The highly microporous carbons were obtained by KOH activation of phenolic resins pyrolyzed at lower temperature (∼500 °C), while high temperature KOH activation (∼800 °C) afforded microporous carbons with preserved mesoporosity.     

Anisotropic electron mobility in fluorene-PPV and fluorene-MEH-PPV

Polyfluorene copolymers are attractive semiconductor materials, in particular for applications in the organic electronics field. They are versatile to be chemically modified and allow a tuning of the emission to cover the entire visible spectrum. A better understanding of the fundamental aspects of the nature of electronic structure and charge transport properties contribute to the improvement of optoelectronic properties of polymeric materials. Here, we provide a structure–property relationship for models of fluorene-PPV and fluorene-MEH-PPV copolymers, using molecular quantum mechanics modelling. The anisotropy is discussed revisiting Mulliken's transition moment theory. Accordingly, our results show that electron mobility occurs preferentially intrachain for both copolymers. Moreover, the interchain electron mobility has the most propensity to occur via π-stacking interactions.     

Textural changes during CO2 activation of chars: A fractal approach

In this paper two series of active carbons obtained at different flow rates of the activating agent, CO₂, are characterized in order to establish the different mechanisms of pore development during the activation step. This study complements previous works on textural development during the different steps in the process of obtaining active carbons: coal oxidation, coal pyrolysis and char gasification. As the characteristics of the original and intermediate materials are of capital importance in the pore development of active carbons, the properties of the active carbons, precursor chars and coals were considered and analyzed together. Mercury porosimetry and helium picnometry were used to determine classical textural parameters as well as to perform a more detailed study of the pore volume generation during the different conditions of the activation step. Data obtained from the mercury porosimetry determinations was also employed for fractal determinations according to the methodologies proposed by Friesen and Mikula, Zhang and Li and the procedure of Neimark. Average surface fractal dimensions as well as fractal profiles and local surface fractal dimensions were calculated. The use of different flow rates during the activation step produces changes not only in the ordinary textural parameters but also in the fractal characteristics of the active carbons. Activation at higher flow rates leads to smoother fractal profiles and also to lower values of the average surface fractal dimensions of the active carbons.     

单斜结构纳米CePO4的控制合成与发光性能研究

利用水热法,调节反应体系中PO3-4/Ce3+摩尔比,低温控制合成了单斜结构CePO4纳米棒及花状纳米团簇.用XRD,FE-SEM,DSC-TG和荧光光谱分析了产物的相结构、晶粒尺寸、形貌及发光性能.结果显示,随PO3-4/Ce3+摩尔比的增加,单斜结构CePO4的合成温度降低,其形貌由棒状演变为花状纳米团簇.当PO3-4/Ce3+摩尔比较低时,得到CePO4纳米棒;当PO3-4/Ce3+摩尔比较高时,得到花状纳米团簇.产物的荧光光谱分析显示一维纳米棒的光致发光性能优于花状纳米团簇.原料H3PO4可重复利用,降低了合成CePO4的成本.     

Hard carbon derived from corn straw piths as anode materials for sodium ion batteries

Hard carbon is considered as the most promising anode material for practical sodium ion batteries. Herein, we report biomass-derived hard carbon made from corn straw piths through a simple carbonization process. X-ray diffraction patterns and Raman spectra elucidated highly disordered structures, and high-resolution transmission electron microscopy confirmed that the hard carbons have many local ordered structures containing turbostratic nanodomains and more nanovoids surround the turbostratic nanodomains. The electrochemical performances of the hard carbons were systematically investigated in sodium ion batteries. By optimizing the carbonization temperature, the sample carbonized at 1400 °C (HC1400) exhibited high reversible capacity of 310 mAh g^?1 and good cycling stability; the capacity can still retain 274 mAh g^?1 after 100 cycles. More importantly, HC1400 can deliver reversible capacity of 206 mAh g^?1 with 79% retention rate after 700 cycles measured at a current density of 200 mA g^?1, which is much better than those in most previous reports. This study provides a way to develop inexpensive, renewable, and recyclable materials from biomasses towards next-generation energy storage applications.