Nitrogen Adsorption-desorption Analysis Research Articles

Insight into Relationship between Thermal Dissolution of Low-Rank Coals and Their Subsequent Oxidative Depolymerization

Oxidative depolymerization of low-rank coals is promising for obtaining benzene carboxylic acids (BCAs). However, it is hindered by the low yield of BCAs along with a large number of alphatic acids. Thermal dissolution could modify the physico-chemical structural features of low-rank coals, which is expected to improve the oxidation of LRCs. In this paper, lignite and subbituminous coal were firstly subjected to thermal dissolution with cyclohexane at 250 °C for 2 h. Then, the raw coal and the corresponding thermal insoluble portion (TIP) were oxidized by NaOCl under the same conditions. The residual yields of TIPs oxidation were both lower than those of raw coals oxidation, indicating that TIPs were more easily oxidized than the raw coals. The yield of BCAs obtained by TIPs oxidation was above 19% higher than that from the oxidation of raw coals. Meanwhile, the selectivity of BCAs was improved in the resulting oxidation products from TIPs compared with that from the raw coals. The relationship between BCAs generation and thermal dissolution of low rank coals was investigated by ultimate analysis, Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption analysis. The results suggested that thermal dissolution could enrich aromatic portion in the remaining TIPs, resulting in an increasing of the yield and selectivity of BCAs. Simultaneously, thermal dissolution raised the specific surface area and expanded the looser space structure of TIPS, which were beneficial for the sufficient collision between aromatic structures and oxidant, facilitating the oxidative depolymerization of TIPs. This investigation would provide a novel route for promoting BCAs production by mild oxidative depolymerization of low-rank coals.

Hierarchically structured LaFeO3 with hollow core and porous shell as efficient sensing material for ethanol detection

Hollow LaFeO3 (LFO-HS) was synthesized by a facile hydrothermal method with the use of cetyltrimethylammonium bromide. Its structural, morphological, microstructural and textual characterizations were performed using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption-desorption analysis. The gas-sensing performance of LFO-HS sensor was studied towards different gases, including ammonia (NH3), ethanol (C2H5OH), acetone (CH3COCH3), and liquefied petroleum gas (LPG). The LFO-HS sensor exhibited p-type gas sensing behavior and enhanced sensing performance towards ethanol gas as compared with bulk LaFeO3 sensor. A rapid, high, and stable response was seen at 300 °C. Meanwhile, a linear response and low limit of detection (1 ppb) to ethanol was observed. After the investigation on sensitivity to different reducing gases, our results revealed that the LFO-HS sensor exhibited good selectivity to ethanol and suggested it being a promising sensor candidate for future practical use in trace ethanol detection.

A comparative study on the thermal stability, textural, and structural properties of mesostructured γ-Al2O3 granules in the presence of La, Sn, and B additives

Mesoporous γ-alumina is widely used as catalyst support in various catalytic reactions of industrial interest. However, due to the instability of γ-alumina at elevated temperatures, many efforts have been reported to inhibit the α-alumina phase transition through doping with suitable metalloids, as well as transition, post-transition, or rare-earth elements. In the present study, undoped and La-, Sn-, and B-doped alumina granules were synthesized via sol-gel/oil drop method with the aim to clarify the role of the additives and their content on the porous structure as well as on the chemical, structural, and microstructural behavior of γ-alumina. XRD and DTA/TG results demonstrated that thermal stability of transition aluminas increases more than 100 °C by 3 wt% lanthanum and tin doping; however, boron doping seems to have only negligible effect on the thermal stability. On the other hand, based on nitrogen adsorption-desorption analysis, tin and boron-doped aluminas showed a higher surface area at 750 °C (between 214.74 m2/g to 245.97 m2/g) but higher loss in the surface area after calcination at 1200 °C (between 25.45 m2/g to 8.57 m2/g). On the contrary, the 3 wt% La-doped alumina sample, with a relatively high surface area at 750 °C (227.17 m2/g), exhibited the highest surface area after calcination at 1200 °C (53.07 m2/g). 27Al MAS NMR and HRTEM studies indicated that the presence of 3 wt% La in alumina structure leads to thermal and mesoporous structure stability up to 1200 °C by inhibiting oxygen lattice restructuring. These results provide a comparative perspective of La, B, and Sn additives' behavior in γ-alumina.

Effects of the Pore Structure of Commercial Activated Carbon on the Electrochemical Performance of Supercapacitors

The performance of activated carbon (AC) can be improved by optimizing the pore structure and increasing the specific surface area. In the present work, seven commercial activated carbons having different pore structures were used to explore the effects of pore morphology on electrochemical characteristics. Nitrogen adsorption-desorption, X-ray diffraction, Raman spectroscopy and electrochemical analyses were used to assess these materials. Trials in aqueous 6 M KOH showed that an AC with a high proportion of ultramicropores (pores less than 1 nm in size) and a suitable mesopore structure provided more charge storage sites. These sites promoted the diffusion of the electrolyte, thereby reducing the internal resistance of the material. Specific capacitance values normalized by specific surface area demonstrated that ultramicropores also enhanced the capacitance values of AC-based electrodes. An optimized specimen having a high ultramicropore volume of 0.41 m3/g and a reasonable mesopore volume of 0.15 m3/g exhibited a specific capacitance of 283.90 F/g at a current density of 1 A/g together with an energy density of 8.47 Wh/kg. This AC also showed superior rate capability and excellent cycling stability with a capacitance retention of 97.16% after 5000 cycles. This study provides guidance that will be helpful in improving commercial AC materials with applications as electrodes in supercapacitors.

Chemical functionalization of chitosan biopolymer and chitosan-magnetite nanocomposite with sulfonic acid for acid-catalyzed reactions

Abstract Chemical functionalization of chitosan biopolymer and chitosan-magnetite nanocomposite was performed with sulfonic acid functional groups to achieve new solid acid materials. The sulfonic acid functional groups were created through the ring opening nucleophilic reaction of amine groups of chitosan with 1,4-butane sultone. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopies (XPS) verified the successful sulfonic acid functionalization of chitosan. The obtained sulfonic acid functionalized chitosan-magnetite nanocomposite showed superparamagnetic properties according to the vibrating sample magnetometry analysis and exhibited magnetic separation feature from dispersed mixtures. Nitrogen adsorption-desorption analysis indicated the increase in surface area after formation of chitosan-magnetite nanocomposite and functionalization with sulfonic acid. Both of the prepared solid acids exhibited high catalytic activities in the acid-catalyzed acetic acid esterification with n-butanol and benzaldehyde acetalization with ethylene glycol as model reactions. Furthermore, they can be reused several times without considerable loss of their activities.

Synthesis, Characterization and Application of Carbon Nanotubes Decorated with Zinc Oxide Nanoparticles for Removal of Benzene, Toluene and p-Xylene from Aqueous Solution

The removal of benzene, toluene and p-xylene (BTX) from water is necessary to avoid various health and environmental concerns. Among various techniques, adsorption is suitable and widely used for the removal of BTX from water. In this study, the adsorption of BTX from water was performed using carbon nanotubes that were impregnated with zinc oxide nanoparticles. The impregnation was performed using the wet impregnation technique. The synthesized materials were characterized using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD) spectroscopy, thermogravimetric analysis (TGA) and nitrogen adsorption–desorption analysis. In batch adsorption experiments, the effect of adsorbent dosage, initial concentration, and contact time were investigated. The percentage removal for a given time and dosage was in the order of p-xylene > toluene > benzene. The kinetics models’ fitting revealed that the pseudo-second-order model fits well the adsorption of benzene, toluene and p-xylene with R2 > 99.4%. The results of adsorption isotherm fitting revealed the best fit with Sips isotherm model (R2 > 99.7%) and the adsorption capacity was p-xylene: 125 mg/g > toluene: 105 mg/g > benzene: 70 mg/g. This behavior is observed probably due to a decrease in solubility and an increase in the molecular weight of BTX.

Correlation analysis between cationic metal characteristics and ion-exchange performance of brick-derived zeolites: A comprehensive mechanistic explanation

A metakaolinite-rich brick originated from Central African Republic was modified with sodium hydroxide according to a zeolitization process. The synthesized material was characterized by means of environmental scanning electron microscopy and X-ray diffraction. Pore size distribution was determined by nitrogen adsorption-desorption analysis. The equilibrium reactions between the Na-exchanged forms of brick-derived zeolites and aqueous solutions containing one, two or three cationic metals (Me2+ = Cd2+, Fe2+, Ni2+ and Pb2+) were studied in the batch mode at room temperature. Experimental equilibrium results were plotted in the form of “ion-exchange isotherms” in order to better interpret data in terms of metals affinity/selectivity. Kielland plots were drawn and thermodynamic equilibrium constant and standard Gibbs free energy were determined for each 2Na+ → Me2+ or Me12+ → Me22+ exchange. Thermodynamic data were analyzed on the basis of both the general properties of divalent metals in water and the surface behavior of the brick. These investigations permitted to show the importance of first hydrated radius, ionic potential and hydration free energy and second kinetics and mass-transfer/diffusion on the course of the ion-exchange process at brick-water interface.

Facile synthesis of MIL-100 metal-organic framework via heatless technique for the adsorptive treatment of cationic and anionic pollutants

The facile synthesis of an iron-based metal-organic framework, MIL-100(Fe) has been successfully conducted via a heatless water-based technique. The unique features have been evaluated with respect to the X-ray diffraction, field emission scanning electron microscopy, nitrogen adsorption-desorption analysis, Fourier transform infrared spectroscopy, and zero point of charge measurement. The adsorptive potential was examined using the cationic (methylene blue, MB) and anionic (naproxen, NPX) water pollutants. The synthesized MIL-100(Fe) sample, MIL-100(FeSO 4 ), owned a crystalline microporous-mesoporous structure, with a large BET surface area of 1984 m 2 /g and total pore volume of 1.096 cm 3 /g. The equilibrium data best conformed to the Langmuir-Freundlich isotherm and pseudo-second order kinetic model, with the maximum adsorption capacity for MB and NPX of 568.1 mg/g and 148.8 mg/g, respectively. Thermodynamic analysis revealed the favorable energetics (Δ G < 0 and Δ S > 0), endothermic (Δ H > 0 for MB) and exothermic nature (Δ H < 0 for NPX) of the adsorption process. Negligible degradation of the adsorptive performance was recorded under high ionic strength solutions and simulated wastewaters. MIL-100(FeSO 4 ) demonstrated great regenerative potential by ethanol stripping for at least 5 regeneration cycles. The present findings provide an invaluable insight into the green synthesis technique of MIL-100(Fe), with high upscaling prospects. Imparted with different surface anionicity and electrically neutral functional sites, MIL-100(FeSO 4 ) has emerged to be a potent adsorbent for the successful treatment of both cationic and anionic water pollutants, even under high-strength water samples with complex water matrices.

Preparation, Characterization and Evaluations of Carbon-Doped Ag/Fe/TiO₂ Mesoporous Nanocomposite Photocatalyst for Degradation of Methylene Blue and Congo Red.

Carbon doped silver/iron/TiO₂ nanocomposite is synthesized via the solvothermal technique. Titanium tetraisopropoxide is used as a TiO₂ source. The composite samples are characterized by different physicochemical methods, including nitrogen adsorption-desorption analysis, transmission electron microscope, scanning electron microscope, X-ray diffraction, photoluminescence, UV-vis, Fourier-transform infrared, and Energy dispersive X-ray spectroscopy. The nanocrystalline structure of the samples with anatase phase having a tetragonal shape is shown by the XRD and TEM analysis. The photo-absorption boundary of pure TiO₂ expands into the visible light region due to composite formation, shown by analysis of UV-vis data. An increase in the degree of electron-hole couple segregation is shown via photoluminescence analysis. N₂ adsorption-desorption analysis manifests the higher surface area of samples along with mesoporous nature. The high photodegradation action is shown by the composite samples as compared to pure mesoporous TiO₂.

Fibrous polyester sponge modified with carboxymethyl cellulose and Zeolitic imidazolate frameworks for methylene blue dye removal in batch and continuous adsorption processes

Zeolitic imidazolate framework materials belong to an important class of Metal-organic frameworks that show attractive applications in various fields including adsorption and chemical separation. In this study, nonwoven fibrous polyester sponge surface was modified by cross-linked carboxymethyl cellulose and synthesized ZIF-8 and used to remove methylene blue dye from aqueous solution. The prepared filter was characterized using Field Scanning Electron Microscopy, Fourier Transform Infrared Spectrometer, X-ray Diffraction, and nitrogen adsorption-desorption analyses, and effects of contact time and dye concentration were investigated in batch and continuous fixed bed dye adsorption processes. Batch kinetics experimental data were estimated with the models of pseudo-first-order, pseudo-second-order, Elovich, and intra-particle, and continuous kinetics experimental data were estimated with Thomas, Adams-Bohart, and Yoon-Nelson models. Batch and continuous adsorption kinetics were more consistent with the pseudo-second-order and the Yoon-Nelson models, respectively. The filter adsorption capacity were 0.824 and 0.829 mg/g in continuous and batch systems at initial concentration of 8 mg/L, respectively. With increasing initial dye concentration from 2 to 8 mg/L, the adsorption capacity was increased about 80 and 90% in batch and continuous systems, respectively. By regeneration experiments after 5 cycles, acceptable results were observed.

Shrinkage behavior of cementitious 3D printing materials: Effect of temperature and relative humidity

Extrusion-based concrete 3D printing is at its infancy and many aspects of this new technology need to be thoroughly investigated to pave the way for its widespread use in construction. Since the inherent drying shrinkage of the hardened cement paste is the source of the drying shrinkage of 3D printed concrete, the shrinkage behavior of cementitious 3D printing materials with very high cement to fine aggregate ratios is one of the major challenges for researchers working on this innovative technology. Besides, due to the absence of formwork in this technique, an outdoor 3D printing environment causes excessive moisture loss and drying shrinkage cracking. This paper presents the first comprehensive investigation on the effects of different outdoor environmental conditions i.e. relative humidity (RH) and temperature on the moisture loss, drying and autogenous shrinkage of cementitious 3D printing materials, considering different sand to cement (S/C), and surface to volume (S/V) ratios of free-formed specimens. Mass loss and length change of mortars which were cured for up to 168 days under standard condition (24 ̊C-50%RH with 24 h of sealed initial curing) were compared with those at 24 ̊C-50%RH, 35 ̊C-85%RH and 35 ̊C-45%RH (free-formed specimens without initial curing) to investigate the effect of outdoor printing environment and the absence of formworks on the deformations caused by shrinkage. The drying shrinkage results indicate that 28 days free-formed specimens under different non-standard curing conditions show a length change up to 30% lower than specimens in the standard environment. Moreover, increasing the sand to cement ratio from 0.8 to 1.0 results in a 10% decrease in the drying shrinkage strain. This study also discusses the higher susceptibility of free-formed specimens to carbonation shrinkage and demonstrates that printed specimens have higher shrinkage deformation in the longer term compared to conventional casting specimens. The results of nitrogen adsorption-desorption analysis also prove that the total porosity in free-formed specimens in all environmental conditions reduces and reaches a finer pore structure after 112 days compared to conventional casting specimens. These results point to the importance of internal or external curing for reducing shrinkage in concrete 3D printing.

Efficient nitrate adsorbent applicable to wide pH range derived from polyacrylonitrile (PAN) fiber

A thermally stabilized polyacrylonitrile (PAN) fiber was activated with sodium carbonate (Na2CO3) at 800 °C (PYR-8SC1) followed by annealing at 950 °C (PYR-8SC1-9.5HT30) to remove negatively charged surface oxygen and supplied for adsorption of nitrate in aqueous solution from acidic to weak basic range. Nitrogen adsorption-desorption analysis was conducted to examine the textural properties of PYR-8SC1-9.5HT30 sample comparing with the non-annealing sample of PYR-8SC1. Elemental analysis was performed to know the content of nitrogen and oxygen in the samples and X-ray photoelectron spectroscopy (XPS) was also applied to determine the amount of quaternary nitrogen (N-Q) species favorable for the nitrate adsorption. PYR-8SC1-9.5HT30 exhibited a stable high adsorption capacity in a wide equilibrium solution pH (pHe) range, particularly around neutral pHe, whereas PYR-8SC1 worked well only in acidic condition at pHe close to 3 or lower. Maintaining high adsorption capacities of nitrate on PYR-8SC1-9.5HT30 could be caused by not only surface exposure of positively charged graphitic N-Q species, but also the presence of positively charged oxygen and the absence of negatively charged pyridine N-oxide (N-X) and the other negatively charged nitrogen and oxygen species that might hinder the nitrate adsorption onto the surface of PAN activated carbon fiber (ACF).

Preparation of Triple-Functionalized Montmorillonite Layers Promoting Thermal Stability of Polystyrene.

The objective of this study was to investigate the effect of three different treatments on the morphology, microstructure, and the thermal characteristics of a montmorillonite (Mt) sample, by using hydrochloric acid (HCl), tributyl tetradecyl phosphonium chloride (TTPC) surfactant, and γ-methacryloxypropyltrimethoxysilane (γ-MPS). The resultant nanofillers were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption–desorption analysis, X-ray fluorescence spectrometry (XRF), and thermogravimetric analysis (TGA). The results showed that the amount of chemical grafting of the γ-MPS was increased after the acid treatment, whereas the amount of intercalation of the TTPC surfactant was decreased. The preintercalation of TTPC or silylation of γ-MPS, for the Mt sample, had a certain hindrance effect on its subsequent silylation or intercalation treatments. Furthermore, the effect of four different nanofillers on the thermal stability properties of the polystyrene (PS) matrix were also investigated. The results showed an increase in thermal stability for the triple-functionalized Mt, compared with the double-functionalized samples. The onset decomposition temperatures and the maximum mass loss temperatures of the PS nanocomposites were increased by 27 °C and 32 °C, respectively, by the incorporation of triple-modified Mt, as a result of the good exfoliation and dispersion of the nanolayers, more favorable polymer–nanofiller interaction, as well as the formation of a more remarkable tortuous pathway in the continuous matrix.

Ship‐in‐bottle preparation of multi‐SO3H functionalized ionic liquid@MIL‐100(Fe) for acid‐catalyzed ring‐opening of epoxides

AbstractThe fact that the homogeneous acid catalysts are usually separated difficulty than heterogeneous catalysts from the reaction media, the opportunity to combine the advantages of both homogeneous and heterogeneous catalytic systems by immobilizing ILs within the pores of a porous solid support host is an alternative method. In this research, a multi‐SO3H functionalized ionic liquid derived from hexamethylenetetramine (HMTA) and 1,3‐propane sultone was entrapped inside the pores of MIL‐100(Fe) through the ship‐in‐bottle method and utilized for heterogeneous acid‐catalyzed ring‐opening of epoxides under solvent‐free conditions. The physicochemical properties of prepared catalyst were fully elucidated by various methods. FT‐IR spectroscopy and elemental analysis approved the successful incorporation of modified groups within the MIL‐100(Fe) cavities. The concentration of acid sites was measured via the acid–base titration which exhibited the 0.9 mmol/g H+ in the catalyst structure. Also, thermogravimetric analysis (TGA) profile showed the loosing of modified groups at 300–600°C. Moreover, X‐ray diffraction (XRD) analysis showed that the MIL‐100(Fe) structure was retained after modification and nitrogen adsorption–desorption analysis (BET method) manifested the decrease in surface area caused by incorporation of ionic liquid. The fabricated catalyst exhibited high catalytic efficiency in methanolysis of styrene oxide (99% conversion in 3 h) under ambient conditions and used without a substantial drop in product yield in further rounds.

Carboxylic acid decorated silica aerogel nanostructure as drug delivery carrier

Surface functionalization of silica aerogel could pioneer great utilities, including the modified release of loaded drugs through the specific interaction that emerged. In this work, the effect of carboxylic modification of silica aerogel on drug loading capacity and drug dissolution rate was studied to evaluate as celecoxib (CCB) delivery carrier. The modification was successfully carried out on calcined ambient pressure dried silica aerogel (SA-OH) through two-step treating with N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane (AEAPTES) and then succinic anhydride. The characterization methods of FT-IR, FE-SEM, nitrogen adsorption-desorption analysis, TGA, DSC, XRD, zeta-potential measurements, and UV-spectrophotometry were used to study the surface modification and drug loading process systematically. The results have shown that the modification to grafting the terminal –COOH groups on the SA-OH were successfully carried out. The modified aerogels have a similar mesoporous structure to the original ones with a smaller mean pore size. After CCB loading on the carriers, its crystallinity state converts to the non-crystalline and amorphous in the SA-OH and SA-COOH carriers, respectively. Besides, loading on SA-COOH benefits the COO − - NH 3 + bonding between carrier and drug functional groups. Drug release results displayed a faster drug dissolution from both carriers than the pure drug, and the controlled release rate was observed from SA-COOH/CCB compared with the SA-OH/CCB due to the existence of stronger bonding and smaller pore size. It was found that SA-COOH has good potential, considering the ability to adjust drug dissolution and exhibiting good biocompatibility on exposure to model cell line. • The silica aerogel with carboxylic acid functional groups (SA-COOH) was successfully synthesized. • The drug release was modified due to molecular drug state and drug-carrier interaction. • Cell viability assay was confirmed the biocompatibility of SA-COOH.

Silver-functionalized UiO-66 metal-organic framework-coated 3D printed device for the removal of radioactive iodine from wastewaters

Silver-functionalized UiO-66 MOF was prepared by an easy one-pot solvothermal reaction and characterized by X-ray diffraction, nitrogen adsorption-desorption, electron microscopy, X-ray spectrometry and thermogravimetric analysis. The prepared functionalized MOF was tested for the removal of radioactive iodine from water, obtaining an outstanding extraction capacity of 131I (~1 MBq/g) due to the excellent affinity of Ag particles to iodide. For practical applications, the obtained porous UiO-66-SO3H@Ag material was incorporated by a simple method into a 3D printed device using polyvinylidene fluoride as binder. The developed UiO-66-SO3H@Ag 3D device showed high efficiency for the removal of 131I, an excellent reusability and good performance for the extraction of 131I from sewage water and hospital waste samples, obtaining in all cases recoveries above 90%.

Magnetic layered double hydroxide/zeolitic imidazolate framework-8 nanocomposite as a novel adsorbent for enrichment of four endocrine disrupting compounds in milk samples

For the first time, a novel nanocomposite, zeolitic imidazolate framework/magnetic layered double hydroxide (Fe3O4@LDH/ZIF), was successfully fabricated through in situ synthetic method with Fe3O4 as magnetic core and composite as shell. The resulting materials were characterized by XRD, TEM, FT-IR, VSM, TGA and nitrogen adsorption-desorption analysis. The Fe3O4@LDH/ZIF was employed as a sorbent in dispersive micro-solid phase extraction (D-μ-SPE) for enrichment of four endocrine disrupting compounds (EDCs) from milk samples prior to ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS) analysis. The synthesized nanocomposite showed bigger specific surface area and better absorption capacity than Fe3O4@LDH. The equilibrium adsorption capacities (Qe, mg/g) of EDCs on the Fe3O4@LDH/ZIF reached up to 47.4–138.8 mg/g, mainly resulting from hydrogen bonding, π-π interaction and electrostatic interaction between EDCs and nanocomposite. Several variables affecting the extraction efficiency were investigated and optimized. The method displays low limits of detection (3–15 ng L−1), good linearity (10–5000 ng L−1), acceptable precision (RSD < 7.8%) and accuracy (RE < 5.2%). Satisfactory repeatability was obtained with RSD in the range of 1.2–7.8%. This work provides a promising approach for the development of new sorbent media in sample preparation for the improvement of analytical performance.

Metallic phase MoS2 nanosheet decorated biomass carbon as sulfur hosts for advanced lithium–sulfur batteries

Constructing an ideal sulfur cathode host with high electronic conductivity, strong polarity, and robust porous network structure is crucial to boosting the electrochemical performance of Lithium–sulfur (Li–S) batteries, but remains a major challenge. Herein, orientation growth of 1T MoS2 nanosheets on biomass carbon (1T MoS2@C) are successfully fabricated by solvothermal approach and then utilized as sulfur host for lithium–sulfur batteries. The structure of 1T MoS2@C composites was examined by X–ray diffraction, Raman spectroscopy, Scanning electron microscopy, X–ray photoelectron spectroscopy and Nitrogen adsorption–desorption analysis etc. Results reveal that the 1T MoS2@C has a well–defined porous structure with high surface area (155.3 m2 g−1). Electrochemical measurements reveal that the 1T MoS2@C/S cathode delivers a high initial capacity of 1090.3 mAh g−1 at 0.2 C and a high–capacity retention of 735.2 mAh g−1 with capacity fade of 0.059% per cycle over 300 cycles at 1 C. This facile and cost–effective strategy for synthesising 1T MoS2@C materials provide a new avenue for the development of low–cost Li–S batteries.

Fabrication of Inorganic Oxide Fiber Using a Cigarette Filter as a Template.

Inorganic oxides with unique physical and chemical properties have attracted much attention because they can be applied in a wide range of fields. Herein, recycled cigarette filters are deacetylated to cellulose filters (CFs), which are then applied as templates to prepare fiber-like inorganic oxides (titanium dioxide, TiO2, and silicon dioxide, SiO2). Inorganic oxides are prepared using CF as a template by a typical sol–gel reaction of metal alkoxides. Owing to the fibrous structure of the CF template, the prepared inorganic oxides (TiO2 and SiO2) show similar fibrous structures, which was confirmed by scanning electron microscopy and nitrogen adsorption–desorption analysis. Moreover, the prepared inorganic oxides (TiO2 and SiO2) show high surface areas and pore volumes. Furthermore, the TiO2 fiber-like materials are evaluated for their photocatalytic properties by analyzing the methylene blue (MB) and methyl orange (MO) degradation. In this study, we provide a clean method, which can convert cellulose acetate-based waste into useful templates to prepare inorganic oxides with relatively simple steps, and the prepared inorganic oxides can be applied in water treatment.

X-ray scattering profiles: revealing the porosity gradient in porous silicon

Porous silicon layers with different porosities were prepared by adjusting the anodization current density of the electrochemical etching process, starting from highly doped p-type crystalline silicon wafers. The microstructural parameters of the porous layers were assessed by high-resolution X-ray diffraction, total external reflection, scanning electron microscopy and nitrogen adsorption–desorption analysis. Furthermore, both the surface porosity and the mean porosity for the entire volume of the samples were estimated by employing total external reflection measurements and X-ray reciprocal-space mapping, respectively. The results clearly indicate that the surface porosity is different from the mean porosity, and the presence of a depth porosity gradient is suggested. To evaluate the porosity gradient in a nondestructive way, a new laboratory method using the grazing-incidence X-ray diffraction technique is reported. It is based on the analysis of the X-ray scattering profiles of the porous layers to obtain the static Debye–Waller factors. In this way, a description of the porosity gradient in a quantitative framework becomes possible, and, as a result, it was shown that the porosity increases exponentially with the X-ray penetration depth. Moreover, a strong dependence between the porosity gradient and the anodization current was demonstrated. Thus, in the case of the lowest anodization current (e.g.50 mA cm−2) a variation of only 15% of the porosity from the surface to the interface is found, but when applying a high anodization current of 110 mA cm−2the porosity close to the bulk interface is almost three times higher than at the surface.