Three-dimensional flower-like and hierarchical porous carbon materials as high-rate performance electrodes for supercapacitors

Three-dimensional flower-like and hierarchical porous carbon material (FHPC) has been fabricated through a simple and efficient carbonization method followed by chemical activation with flower-like ZnO as template and pitch as carbon precursor. The hierarchical porous structure is composed of numerous micropores and well-defined mesopores in the interconnected macroporous walls. The FHPC electrode can achieve a relatively high capacitance of 294 F g⁻¹ at a scan rate of 2 mV s⁻¹ and excellent rate capability (71% retention at 500 mV s⁻¹) with superior cycle stability (only 2% loss after 5000 cycles) in 6 mol L⁻¹ KOH electrolyte. The symmetric supercapacitor fabricated with FHPC electrodes delivers a high energy density of 15.9 Wh kg⁻¹ at a power density of 317.5 W kg⁻¹ operated in the voltage range of 0–1.8 V in 1 mol L⁻¹ Na₂SO₄ aqueous electrolyte.     

Fabrication of magnetic polybenzoxazine-based carbon nanofibers with Fe3O4 inclusions with a hierarchical porous structure for water treatment

Hierarchical porous, magnetic Fe₃O₄@carbon nanofibers (Fe₃O₄@CNFs) based on polybenzoxazine precursors have been synthesized by a combination of electrospinning and in situ polymerization. The benzoxazine monomers could easily form thermosetting nanofibers by in situ ring-opening polymerization and subsequently be converted into CNFs by carbonization. The resultant fibers with an average diameter of 130 nm are comprised of carbon fibers with embedded Fe₃O₄ nanocrystals, and could have a high surface area of 1885 m² g^?1 and a porosity of 2.3 cm³ g^?1. Quantitative pore size distribution and fractal analysis were used to investigate the hierarchical porous structure using N₂ adsorption and synchrotron radiation small-angle X-ray scattering measurements. The role of precursor composition and activation process for the effects of the porous structure is discussed, and a plausible correlation between surface fractal dimension and porous parameter is proposed. The Fe₃O₄@CNFs exhibit efficient adsorption for organic dyes in water and excellent magnetic separation performance, suggesting their use as a promising adsorbent for water treatment, and also provided new insight into the design and development of a carbon nanomaterial based on a polybenzoxazine precursor.     

Synthesis of LiFePO4/carbon composite from nano-FePO4 by a novel stearic acid assisted rheological phase method

LiFePO₄/carbon composite was synthesized at 600 °C for 4 h in an Ar atmosphere by a stearic acid assisted rheological phase method using amorphous nano-FePO₄ as the iron source. XRD, SEM and TEM observations show that the LiFePO₄/carbon composite has good crystallinity, ultrafine and well-dispersed particles of 60–150 nm size and in situ carbon coated on the surface of LiFePO₄ crystallites. The synthesized LiFePO₄/carbon composite shows a high discharge capacity of 160 mAh g⁻¹ and 155 mAh g⁻¹ at rates of 0.5 C and 1 C, respectively. Even at a high current density of 30 C, the material still presents a discharge capacity of 93 mAh g⁻¹ and exhibits an excellent cycling performance.     

Analysis of tetramethylammonium–montmorillonite and retention of toluene from aqueous solution

Non-ionic organic contaminants, such as toluene, can be effectively absorbed by organo-montmorillionite. The tetramethylammonium (TMA)–montmorillonites were prepared by ion-exchange and used to evaluate toluene uptake from water. The TMA–montmorillonites were characterized by total organic carbon determinations, swelling index, X-ray diffraction, thermal analyses, and infrared spectroscopy. Toluene adsorption was measured by UV–visible spectrophotometry. The thermal stability of the TMA–montmorillonites decreased as TMA addition increased; the total mass loss decreased with increasing temperature up to 500 °C. The amount of carbon retained by the TMA–montmorillonites was proportional to the area of the infrared band at 1488 cm^− 1 (asymmetric C–H bending vibration of –CH3 group). The retention of toluene by TMA–montmorillonites increased from 0.2 to 0.22 mg g^− 1 mainly to interlayer adsorption. The adsorption of toluene influenced the OH-stretching vibration.     

Polymer-derived mesoporous Ni/SiOC(H) ceramic nanocomposites for efficient removal of acid fuchsin

In this paper, magnetic porous Ni-modified SiOC(H) ceramic nanocomposites (Ni/SiOC(H)) were successfully prepared via a template-free polymer-derived ceramic route, which involves pyrolysis at 600 °C of nickel-modified allylhydridopolycarbosilane (AHPCS-Ni) precursors synthesized by the reaction of allylhydridopolycarbosilane (AHPCS) with nickel(II)acetylacetonate (Ni(acac)₂). The resultant Ni/SiOC(H) nanocomposites are comprised of in-situ formed nanoscaled Ni socialized with small amounts of NiO and nickel silicides embedded in the amorphous SiOC(H) matrix. The materials show ferromagnetic behavior and excellent magnetic properties with the saturation magnetization in the range of 1.71–7.08 emu g⁻¹. Besides, the Ni/SiOC(H) nanocomposites are predominantly mesoporous with a high BET surface area and pore volume in the range of 253–344 and 0.134–0.185 cm³ g⁻¹, respectively. The measured porosity features cause an excellent adsorption capacity towards a template dye acid fuchsin with the adsorption capacity Q_t at 10 min of 80.7–85.8 mg g⁻¹ and the Q_e at equilibrium of 123.8–129.8 mg g⁻¹.     

A mechano- and electrochemically controlled SnSb/C nanocomposite for rechargeable Li-ion batteries

At present, graphite (LiC₆: 372 mAh g⁻¹, 840 mAh cm⁻³) is used as the anode material for lithium-ion batteries. However, methods to enhance the energy density, cyclability, initial Coulombic efficiency, and rate capability of lithium-ion batteries are still actively being researched. Here, we report a simple, fast, and novel method for transforming micron-sized Sn and Sb powders into ca. 10 nm- and 2–3 nm-sized SnSb crystallites by mechanochemical synthesis and electrochemical reactions, respectively. These nanocrystallites are uniformly distributed in an amorphous carbon matrix, resulting in a SnSb/C nanocomposite structure. The fabricated SnSb/C nanocomposite showed excellent electrochemical properties, such as a high energy density (1st charge: 706 mAh g⁻¹), long cyclability (ca. 550 mAh g⁻¹ over 300 cycles), good initial Coulombic efficiency (ca. 81%), and a fast rate capability (1C: 590 mAh g⁻¹, 2C: 550 mAh g⁻¹).     

An effective and simple way to synthesize LiFePO4/C composite

The cathode material is synthesized from FeC₂O₄·2H₂O and LiH₂PO₄ by a solid-state reaction using citric acid as a carbon source. The electric conductivity of the synthesized LiFePO₄ has been raised by eight orders of magnitude from 10⁻⁹ S cm⁻¹. The LiFePO₄/C composite shows a greatly enhanced rate performance and the cyclic stability at room temperature. It delivers an initial discharge capacity of 128 mAh g⁻¹ at 4C, which is retained as high as 92% after 1000 cycles. In addition, the tested low temperature character is attractive. At −20 °C, the composite exhibits a discharge capacity of 110 mAh g⁻¹ at 0.1C. The homogenous morphology, the porous surface, the small particles inside and the conductive carbon observed contribute much to obtain the favorable electrochemical performance.     

Preparation and electrochemical performance of micro-nanostructured nickel

Micro-nanostructured nickel has been prepared as anode materials for Li ion batteries, via a rheological phase reaction method. Ni₂C₂O₄·xH₂O (x = 2 or 2.5) as precursors are obtained from the solid–liquid rheological mixture of (NH4)₂C₂O₄·H₂O and Ni(NO₃)₂. The nickel powders are prepared by thermal decomposition of the precursors. The structural, morphological and electrochemical performance are investigated by means of thermogravimetry (TG), differential scanning calorimetry (DSC), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and typical electrochemical tests. The micro-nanostructured nickel displays an initial discharge capacity of 457 mAh g⁻¹. It also has a remarkable cycling stability with an average capacity fade of 0.17% per cycle from 13th to 50th cycle in 0.01–3.00 V versus Li at a constant current density of 100 mA g⁻¹.     

Hydrothermal synthesis and characterization of copper containing crystalline silicate mesoporous materials from gel mixture

Novel copper-containing crystalline silicate mesoporous materials (SCMM) have been synthesized by the hydrothermal treatment of slurries of silicon–magnesium–copper hydroxide precipitates along with quaternary ammonium salt. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed a house-of-cards type structure consists of very thin platy silicates. Nitrogen adsorption–desorption isotherms of calcined material show that it has a high surface area (550 m² g⁻¹) and porosity properties. Pore characteristics are similar to that of MCM-41 and FSM-16, and fine-tuning of the pore size was achieved easily by modulating the synthesis temperature. Identification and the location of copper species in Cu-SCMM were done by X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR), respectively. ESR data of air-dried Cu-SCMM consist of clearly defined g_||=2.34, A_||=140×10⁻⁴ cm⁻¹ and g=2.08 at room temperature and g_||=2.34, A_||=160×10⁻⁴ cm⁻¹ and g=2.10 at 77 K. The resulting material exhibited superior catalytic activity towards the hydrogenation of α–β unsaturated aldehyde in supercritical carbon dioxide.     

From non-porous crystalline to amorphous microporous metal(IV) bisphosphonates

Porous layered hybrid materials have been prepared by the reaction of organo-bisphosphonate ligands, 4-(4′-phosphonophenoxy)phenylphosphonic, 4,4′-biphenylenbisphosphonic and phenylphosphonic acids, with metal(IV) cations (Zr and Sn). Crystalline Zr(IV) and Sn(IV) layered bisphosphonates were also prepared, which were non-porous. The amorphous M(IV) bisphosphonates showed variable compositions and textural properties ranging from mainly mesoporous to highly microporous solids with BET surface areas varying from 300 to 480 m² g⁻¹, micropore volumes ranging 0.10–0.20 cm³/g, and narrow porous size distributions for some materials. N₂ isotherms suggest that Sn(IV) derivatives show a comparatively higher micropore contribution than the Zr(IV) analogous at least for the ether-bisphosphonate hybrids. Sn(IV) bisphosphonates exhibit high microporosities without the need of using harmful DMSO as solvent. If ether-bisphosphonic acid is partially replaced by less expensive phenylphosphonic ligand, porous products are also obtained. ³¹P and ¹⁷F MAS NMR and XPS data revealed the presence of hydrogen-phosphonate groups and small (F⁻, Cl⁻ and OH⁻) anions, which act as spacer ligands within the inorganic layers, in these hybrid materials. The complexity of the inorganic layers is higher for the Sn(IV) bisphosphonates likely due to the larger amount of small bridging anions including fluorides. It is suggested that the presence of these small inorganic ligands may be a key factor influencing both, the interaction of the inorganic layer with the bisphosphonate groups, which bridge the inorganic layers, and the generation of internal voids within a given inorganic layer. Preliminary studies of gases adsorption (H₂ and NO) have been carried out for selected Sn(IV) bisphosphonates. The H₂ adsorption capacity at 77 K and 1 bar was low, 0.26 wt%, but the NO adsorption capacity at 1 bar and 298 K was relatively high, 4.2 wt%. Moreover, the hysteresis in the NO isotherms is indicative of partial strong irreversible adsorption of NO.     

Intrinsic kinetics of Fischer–Tropsch reactions over an industrial Co–Ru/γ-Al2O3 catalyst in slurry phase reactor

The rate of Fischer–Tropsch synthesis over an industrial well-characterized Co–Ru/γ-Al₂O₃ catalyst was studied in a laboratory well mixed, continuous flow, slurry reactor under the conditions relevant to industrial operations as follows: temperature of 200–240 °C, pressure of 20–35 bar, H₂/CO feed ratio of 1.0–2.5, gas hourly space velocity of 500–1500 N cm³ g_cat^− 1 h^− 1 and conversions of 10–84% of carbon monoxide and 13–89% of hydrogen. The ranges of partial pressures of CO and H₂ have been chosen as 5–15 and 10–25 bar respectively. Five kinetic models are considered: one empirical power law model and four variations of the Langmuir–Hinshelwood–Hougen–Watson representation. All models considered incorporate a strong inhibition due to CO adsorption. The data of this study are fitted fairly well by a simple LHHW form − R_H2 + CO = ap_H2^0.988p_CO^0.508 / (1 + bp_CO^0.508)² in comparison to fits of the same data by several other representative LHHW rate forms proposed in other works. The apparent activation energy was 94–103 kJ/mol. Kinetic parameters are determined using the genetic algorithm approach (GA), followed by the Levenberg–Marquardt (LM) method to make refined optimization, and are validated by means of statistical analysis. Also, the performance of the catalyst for Fischer–Tropsch synthesis and the hydrocarbon product distributions were investigated under different reaction conditions.     

Ultra-high specific capacitance of self-doped 3D hierarchical porous turtle shell-derived activated carbon for high-performance supercapacitors

The turtle shell of biomass waste is used as raw material, and the natural inorganic salt contained in it is used as a salt template in combination with a chemical activation method to successfully prepare a high-performance activated carbon with hierarchical porous structure. The role of hydroxyapatite (HAP) and KOH in different stages of preparation was investigated. The prepared turtle shell-derived activated carbon (TSHC-5) has a well-developed honeycomb pore structure, which gives it a high specific surface area (SSA) of 2828 m² g^?1 with a pore volume of 1.91 cm³ g^?1. The excellent hierarchical porous structure and high heteroatom content (O 6.88%, N 5.64%) allow it to have an ultra-high specific capacitance of 727.9 F g^?1 at 0.5 A g^?1 with 92.27% of capacitance retention even after 10,000 cycles. Excitingly, the symmetric supercapacitor assembled from TSHC-5 activated carbon exhibits excellent energy density and cycling stability in a 1 M Na₂SO₄ aqueous solution. The energy density is 45.1 Wh·kg^?1 at a power density of 450 W kg^?1, with 92.05% capacitance retention after 10,000 cycles. Therefore, turtle shell-derived activated carbon is extremely competitive in sustainable new green supercapacitor electrode materials.     

Removal of heavy metal ions by dithiocarbamate-anchored polymer/organosmectite composites

In this study, the dithiocarbamate-anchored polymer/organosmectite composites were prepared for the removal of heavy metal ions (lead, cadmium and chromium) from aqueous media containing different amounts of these ions (50–750 ppm) and at different pH values (2.0–8.0). Initially, the modification of the natural smectite minerals was performed by treatment with quartamin styrene and chloromethylstyrene. Then, modified smectite nanocomposites were reacted with carbondisulfide, in order to incorporate dithiocarbamate functional groups into the nanolayer of organoclay. The dithiocarbamate-anchored nano-composites have been characterized by FTIR and used in the adsorption–desorption process. The maximum adsorptions of heavy metal ions onto the dithiocarbamate-anchored polymer/organosmectite composites from their solution was 170.7 mg g^− 1 for Pb(II); 82.2 mg g^− 1 for Cd(II) and 71.1 mg g^− 1 for Cr(III). Competition between heavy metal ions (in the case of adsorption from mixture) yielded adsorption capacities of 70.4 mg g^− 1 for Pb(II); 31.8 mg g^− 1 for Cd(II) and 20.3 mg g^− 1 for Cr(III). Desorption of the heavy metal ions from composite was studied in 0.5 M NaCl and very high desorption rates, greater than 93%, were achieved in all cases. Adsorption–desorption cycles showed the feasibility of repeated uses of this nanocomposite.     

Enhanced CO2/N2 selectivity in amidoxime-modified porous carbon

In this work, we examine the use of the amidoxime functional group grafted onto a hierarchical porous carbon framework for the selective capture and removal of carbon dioxide from combustion streams. Measured CO₂/N₂ ideal selectivity values for the amidoxime-grafted carbon were significantly higher than the pristine porous carbon with improvements of 65%. Though the overall CO₂ capacity decreased slightly for the activated carbon from 4.97 mmol g⁻¹ to 4.24 mmol g⁻¹ after surface modification due to a reduction in the total surface area, the isosteric heats of adsorption increased after amidoxime incorporation indicating an increased interaction of CO₂ with the sorbent. Total capacity was reproducible and stable after multiple adsorption/desorption cycles with no loss of capacity suggesting that modification with the amidoxime group is a potential method to enhance carbon capture.     

Synthesis and characterization of a polystyrenic resin functionalized by catechol: Application to retention of metal ions

Chelating solid phase extraction is a preconcentration method adapted for metal ions extraction in water and requires functionalization of a solid sorbent by an organic ligand. A new chelating resin has been prepared by grafting catechol on Amberlite^® XAD-4 with an imine bridge and reducing it to enhance stability of the modified resin. Synthesis was first carried out at molecular level to validate experimental conditions, optimize yields and facilitate characterization of solid sorbent (particularly by FTIR). Each synthesis step of grafting on Amberlite^® XAD-4 was characterized by FTIR, Py-GC–MS and TGA-DSC. BET measurements showed a decrease in specific area after grafting from 865 to 425 m² g⁻¹ and in total pore volume from 1.19 to 0.66 cm³ g⁻¹. The grafting rate of 33% was determined by back titration of –OH (0.31 ± 0.03 mmol g⁻¹ of resin) and –NH-functions (0.93 ± 0.02 mmol g⁻¹ of resin). The increase in the sorbent hydrophilicity was confirmed by evaluating the water regain. Finally the retention properties of Cd(II), Cu(II), Ni(II) and Pb(II) were determined by ICP-AES at a pH range from 2 to 9. Retention rates of 94% and 98% were found at pH 8 for Cu(II) and Pb(II), respectively. Sorption capacities of 25.8 ± 2.5 μmol g⁻¹ for Cd(II), 89.7 ± 8.4 μmol g⁻¹ for Cu(II), 49.0 ± 10.5 μmol g⁻¹ for Ni(II) and 31.5 ± 1.6 μmol g⁻¹ for Pb(II) were measured.     

Graphitic mesoporous carbons synthesised through mesostructured silica templates

In this paper the fabrication and characterization of graphitizable and graphitized porous carbons with a well-developed mesoporosity is described. The synthetic route used to prepare the graphitizable carbons was: (a) the infiltration of the porosity of mesoporous silica with a solution containing the carbon precursor (i.e. poly-vinyl chloride, PVC), (b) the carbonisation of the silica–PVC composite and (c) the removal of the silica skeletal. Carbons obtained in this way have a certain graphitic order and a good electrical conductivity (0.3 S cm⁻¹), which is two orders larger than that of a non-graphitizable carbon. In addition, these materials have a high BET surface area (>900 m² g⁻¹), a large pore volume (>1 cm³ g⁻¹) and a bimodal porosity made up of mesopores. The pore structure of these carbons can be tailored as a function of the type of silica selected as template. Thus, whereas a graphitizable carbon with a well-ordered porosity is obtained from SBA-15 silica, a carbon with a wormhole pore structure results when MSU-1 silica is used as template. The heat treatment of a graphitizable carbon at a high temperature (2300 °C) allows it to be converted into a graphitized porous carbon with a relatively high BET surface area (260 m² g⁻¹) and a porosity made up of mesopores in the 2–15 nm range.     

Preparation and carbon dioxide uptake capacity of N-doped porous carbon materials derived from direct carbonization of zeolitic imidazolate framework

The preparation, characterization and CO₂ uptake performance of N-doped porous carbon materials and composites derived from direct carbonization of ZIF-8 under various conditions are presented for the first time. It is found that the carbonization temperature has remarkable effect on the compositions, the textural properties and consequently the CO₂ adsorption capacities of the ZIF-derived porous materials. Changing the carbonization temperature from 600 to 1000 °C, the composites and the resulting porous carbon materials possess a tuneable nitrogen content in the range of 7.1–24.8 wt%, a surface area of 362–1466 m² g⁻¹ and a pore volume of 0.27–0.87 cm³ g⁻¹, where a significant proportion of the porosity is contributed by micropores. These N-doped porous composites and carbons exhibit excellent CO₂ uptake capacities up to 3.8 mmol g⁻¹ at 25 °C and 1 bar with a CO₂ adsorption energy up to 26 kJ mol⁻¹ at higher CO₂ coverages. The average adsorption energy for CO₂ is one of the highest ever reported for any porous carbon materials. Moreover, the influence of textural properties on CO₂ capture performance of the resulting porous adsorbents has been discussed, which may pave the way to further develop higher efficient CO₂ adsorbent materials.     

Influence of the type of sepiolite on the modification of the pore-size distribution in γ-Al2O3 supports

γ-Al₂O₃ modified supports with bimodal pore-size distributions were prepared by the addition of different types of natural sepiolites (α or β) into alumina. The supports were characterized by nitrogen physisorption, mercury porosimetry, X-ray diffraction, HRTEM and DTA techniques. A wide range of S_BET (94–238 m² g^− 1), pore volumes (0.3–0.82 cm³ g^− 1), and pore sizes were obtained in the supports depending on the type of sepiolite and its concentration added into alumina. The pore sizes were distributed as follows: mesopores around 1.8 nm in radius, mesopores in the radius range 3.0–25 nm and macropores between 25 and 300 nm in radius. The shape of the pore-size distributions depended on the type of sepiolite: the modal peak for pores larger than 3.0 nm was broad with β-type sepiolites and narrow with α-type sepiolites. The mesopore and macropore sizes can be controlled by the type of sepiolite as well as its concentration added to alumina.     

Adsorption thermodynamics and kinetics study for the self-assembly of 1,8,15,22-tetraaminophthalocyanatocobalt(II) on glassy carbon surface

Spontaneous adsorption of 1,8,15,22-tetraaminophthalocyanatocobalt(II) (4α-Co^IITAPc) on glassy carbon (GC) electrode leads to the formation of a stable self-assembled monolayer (SAM). Since the SAM of 4α-Co^IITAPc is redox active, its adsorption on GC electrode was followed by cyclic voltammetry. SAM of 4α-Co^IITAPc on GC electrode shows two pairs of well-defined redox peaks corresponding to Co^III/Co^II and Co^IIIPc⁻¹/Co^IIIPc⁻². The surface coverage (Γ) value, calculated by integrating the charge under Co^II oxidation, was used to study the adsorption thermodynamics and kinetics of 4α-Co^IITAPc on GC surface. Cyclic voltammetric studies show that the adsorption of 4α-Co^IITAPc on GC electrode has reached the saturation coverage (Γ_s) within 3 h. The Γ_s value for the SAM of 4α-Co^IITAPc on GC electrode was found to be 2.37 × 10⁻¹⁰ mol cm⁻². Gibbs free energy (ΔG_ads) and adsorption rate constant (k_ad) for the adsorption of 4α-Co^IITAPc on GC surface were found to be −16.76 kJ mol⁻¹ and 7.1 M⁻¹ s⁻¹, respectively. The possible mechanism for the self-assembly of 4α-Co^IITAPc on GC surface is through the addition of nucleophilic amines to the olefinic bond on the GC surface in addition to a meager contribution from π stacking. The contribution of π stacking was confirmed from the adsorption of unsubstituted phthalocyanatocobalt(II) (CoPc) on GC electrode. Raman spectra for the SAM of 4α-Co^IITAPc on carbon surface shows strong stretching and breathing bands of Pc macrocycle, pyrrole ring and isoindole ring. Raman and CV studies suggest that 4α-Co^IITAPc is adopting nearly a flat orientation or little bit tilted orientation.     

Formation and electrochemical properties of composites of the C60–Pd polymer and multi-wall carbon nanotubes

Preparation and electrochemical properties of a novel type of the composite made of multi-wall carbon nanotubes (MWCNTs) and two-component polymer of palladium and C₆₀ (C₆₀–Pd) were investigated using cyclic voltammetry, electrochemical impedance spectroscopy, and piezoelectric microgravimetry. A composite film was prepared by electrochemical deposition of C₆₀–Pd on the layer of MWCNTs immobilized on the electrode surface. The polymer forms islands of shells on the carbon multi-wall core. This composite is electrochemically active in the negative potential range due to the electroreduction of the fullerene moiety. In this potential range, specific pseudo-capacitance of the film of the MWCNT/C₆₀–Pd composite is 425 F g⁻¹ in the acetonitrile solution of tetra(n-butyl)ammonium perchlorate. The presence of MWCNTs makes the composite conductive also at potentials less negative than potentials of the C₆₀ electroreduction. The double-layer specific capacitance of this film is close to 15 F g⁻¹.