The effect of activation technology on the electrochemical performance of calcium carbide skeleton carbon

Porous CaC₂-derived carbon (CCDC) was synthesized by one-step route from CaC₂ in a freshly prepared chlorine environment at lower temperature. As-prepared CCDC was activated by H₃PO₄, ZnCl₂, and KOH, respectively. The effects of the activation technology on the structure and morphology of CCDC were studied by X-ray diffraction, physical N₂ adsorption/desorption, and transmission electron microscopy. It has been found that the pore structure and specific surface area of CCDC are apparently improved after activation; the CCDC activated by KOH especially showed an excellent specific surface area of 1,100?m²?g^?1. The electrochemical performance of supercapacitors using activated CCDC as electrode active material was studied by cyclic voltammery, galvanostatic charge/discharge, and cycle life measurements. The results indicated that the CCDCs activated by H₃PO₄, ZnCl₂, and KOH revealed enhanced capacitances of 172.6, 198.1, and 250.1?F?g^?1 in 6?M KOH electrolyte, which were increased by 11.4, 27.8, and 61.2?% compared with the pristine CCDC (155?F?g^?1), respectively. Furthermore, the supercapacitors using all activated CCDCs as electrode active material exhibited excellent cycle stability, and the specific capacitance for all activated CCDC samples had nearly no change after 5,000 cycles.     

Preparation and Characterization of Mesoporous Ce0.5Zr0.5O2 Mixed Oxide

Mesoporous （MSU） Ce0.5Zr0.5O2 mixed oxide with a high specific surface area has been synthesized under weak acidic condition in the presence of an anionic surfactant, sodium dodecylbenzenesulfonate. The effect of the pH value on the formation of mesostructure and the thermal stability of the material has been evaluated. The products were characterized by transmission electron microscopy, powder X-ray diffraction and nitrogen adsorption-desorption measurements. The results showed that the as-prepared Ce0.5Zr0.5O2 mixed oxide possessed a specific surface area of 163.3 m^2·g^-1, which had a cubic fluorite-type structure and possessed specific surface areas of 148.4 and 62.4 m^2·g^-1 after calcination at 500 and 800 ℃ for 2 h, respectively. The material showed excellent thermal stability.     

Porphyrin‐based covalent triazine frameworks: Porosity,adsorption performance,and drug delivery

Two porous porphyrin‐based covalent triazine frameworks (PCTFs), in which porphyrin is incorporated as building block, have been synthesized by the Friedel–Crafts reaction. The copolymer PCTFs show large Brunauer–Emmett–Teller specific surface area of up to 1089 m² g^?1, high CO₂ uptake capacity reaching 139.9 mg g^?1 at 273 K/1.0 bar, and good selectivity for CO₂/CH₄ adsorption attaining 6.1 at 273 K/1.0 bar. The resulting porous solids also can be used as matrices for drug delivery of ibuprofen in vitro. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 2594–2600     

N,B, Si-tridoped mesoporous TiO<Subscript>2</Subscript> with high surface area and excellent visible-light photocatalytic activity

N, B, Si-tridoped mesoporous TiO₂, together with N-doped, N, B-codoped and N, Si-codoped TiO₂, was prepared by a modified sol–gel method. The samples were characterized by wide-angle X-ray diffraction (WAXRD), N₂ adsorption–desorption, transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, UV–visible adsorbance spectra (UV–vis) and X-ray photoelectron spectra (XPS). The N, B, Si-tridoped mesoporous TiO₂ showed small crystallite size, large specific surface area (350 m²/g), uniform pore distribution (3.2 nm) and strong absorption in the visible light region. The photocatalytic activities of the samples were evaluated by the photodegradation of 2,4-dichlorophenol (2,4-DCP) aqueous solution. The N, B, Si-tridoping sample exhibited much higher photocatalytic activity compared with other synthesized photocatalysts. The high activity could be attributed to the strong absorption in the visible light region, large specific surface area, small crystallite size, large amount of surface hydroxyl groups, and mesoporosity.     

Synthesis, network structure and morphology of s-triazine-organosilane glassy hybrid materials

A series of five hybrid materials are synthesized by the reaction of cyanuric chloride (C₃N₃Cl₃) with different alkoxysilanes (R_xSi(OC₂H₅)_4−x, R=CH₃, C₆H₅ and x=0, 1, 2) in ethanol using sol–gel technique. The resulting s-triazine-organosilane products were examined using spectroscopic (UV–visible, FT-IR), thermal (thermogravimetric analysis, TGA), powder X-ray diffraction (P-XRD), BET analysis and microscopic (scanning electron microscopy, SEM) techniques. These hybrid materials exhibit globular and two-dimensional morphological textures with varying degrees of crystalline microstructures. Depending on the functionality of the organosilane building blocks the obtained hybrid materials exhibit different material characteristics including their solid state, Vicat softening point (Vicat hardness), density and porosity. BET surface area measurements indicate that these materials possess small specific surface areas of 0.36–2.3 m²/g with external surface area of ~0.02 m²/g. The phenyl-containing hybrids exhibit pronounced hydrolytic stability compared to the methyl- and silica-based analogs. The DMSO and sulfolane solutions of the prepared hybrids are transparent to visible light whereas their cold-compressed discs are optically opaque.     

Adsorption of acid and basic dyes on NiO-SiO2 composites

A series of composites containing 2.5–21.0% NiO on a surface of macroporous silica is synthesized. The specific surface area of the composites measured by the thermal desorption of nitrogen decreases with an increase in the NiO content from 24 for the original silica carrier to 16 m²/g the for composite containing 21.0% NiO. The basic dye, methylene blue (MB), is only adsorbed on SiO₂ in water solutions, while acid blue anthraquinone (ABA) is only adsorbed on the NiO. The effective specific surface area Seff and effective diameters D _eff of NiO nanoparticles are calculated from the adsorption isotherms of ABA on NiO composites and on NiO synthesized without a carrier. S _eff of NiO nanoparticles decreases from 76 to 42 m²/g and D _eff increases from 8 to 14 nm with rising NiO content in the composites. The NiO nanoparticles synthesized without a carrier are characterized by the lowest S _eff (30 m²/g) and the largest D _eff (20 nm).     

Phenol-formaldehyde resin route to the synthesis of several iron group transition metal phosphides

Abstract

A series of iron, cobalt and nickel metal phosphides of chemical formula Fe_xP, Co₂P and Ni₂P with high specific surface areas of 331.1, 294.2 and 228.0 m² g^?1, respectively, was firstly synthesized by phenol-formaldehyde resin route. It was found that the as-prepared Co₂P and Ni₂P samples synthesized using phenol-formaldehyde resin as a carbon source showed much higher BET surface areas than those prepared using other carbon sources reported before, including cinnamic strong alkali anion exchange resin, p-phenylenediamine and hexamethylenetetramine. This phenol-formaldehyde resin route was proved to be as universal as traditional H₂ reduction method.     

Highly Dispersible Hexagonal Carbon–MoS2–Carbon Nanoplates with Hollow Sandwich Structures for Supercapacitors

MoS₂, a typical layered transition-metal dichalcogenide, is promising as an electrode material in supercapacitors. However, its low electrical conductivity could lead to limited capacitance if applied in electrochemical devices. Herein, a new nanostructure composed of hollow carbon–MoS₂–carbon was successfully synthesized through an l -cysteine-assisted hydrothermal method by using gibbsite as a template and polydopamine as a carbon precursor. After calcination and etching of the gibbsite template, uniform hollow platelets, which were made of a sandwich-like assembly of partial graphitic carbon and two-dimensional layered MoS₂ flakes, were obtained. The platelets showed excellent dispersibility and stability in water, and good electrical conductivity due to carbon provided by the calcination of polydopamine coatings. The hollow nanoplate morphology of the material provided a high specific surface area of 543 m² g⁻¹, a total pore volume of 0.677 cm³ g⁻¹, and fairly small mesopores (≈5.3 nm). The material was applied in a symmetric supercapacitor and exhibited a specific capacitance of 248 F g⁻¹ (0.12 F cm⁻²) at a constant current density of 0.1 A g⁻¹; thus suggesting that hollow carbon–MoS₂–carbon nanoplates are promising candidate materials for supercapacitors.     

A Robust 3D Cage‐like Ultramicroporous Network Structure with High Gas‐Uptake Capacity

A three‐dimensional (3D) cage‐like organic network (3D‐CON) structure synthesized by the straightforward condensation of building blocks designed with gas adsorption properties is presented. The 3D‐CON can be prepared using an easy but powerful route, which is essential for commercial scale‐up. The resulting fused aromatic 3D‐CON exhibited a high Brunauer–Emmett–Teller (BET) specific surface area of up to 2247 m² g^?1. More importantly, the 3D‐CON displayed outstanding low pressure hydrogen (H₂, 2.64 wt %, 1.0 bar and 77 K), methane (CH₄, 2.4 wt %, 1.0 bar and 273 K), and carbon dioxide (CO₂, 26.7 wt %, 1.0 bar and 273 K) uptake with a high isosteric heat of adsorption (H₂, 8.10 kJ mol^?1; CH₄, 18.72 kJ mol^?1; CO₂, 31.87 kJ mol^?1). These values are among the best reported for organic networks with high thermal stability (ca. 600 °C).     

Tuning of Microenvironment in Covalent Organic Framework via Fluorination Strategy promotes Selective CO2 Capture

Herein, we have designed and synthesized two heteroatom (N, O) rich covalent organic frameworks (COF), PD-COF and TF-COF , respectively, to demonstrate their relative effect on CO₂ adsorption capacity and also CO₂/N₂ selectivity. Compared to the non-fluorinated PD-COF (BET surface area 805 m² g⁻¹, total pore volume 0.3647 ccg⁻¹), a decrease in BET surface area and also pore volume have been observed for fluorinated TF-COF due to the incorporation of fluorine to the porous framework (BET surface area 451 m² g⁻¹, total pore volume 0.2978 ccg⁻¹). This fact leads to an enormous decrease in the CO₂ adsorption capacity and CO₂/N₂ selectivity of TF-COF , though it shows stronger affinity towards CO₂ with a Qst of 37.76 KJ/mol. The more CO₂ adsorption capacity by PD-COF can be attributed to the large specific surface area with considerable amount of micropore volume compared to the TF-COF . Further, PD-COF exhibited CO₂/N₂ selectivity of 16.8, higher than that of TF-COF (CO₂/N₂ selectivity 13.4).     

介孔α-Fe2O3表面配合反应平衡常数测定

采用十二胺为模板剂、氨水做沉淀剂成功制备了介孔α-Fe₂O₃, 通过粉末X射线衍射(XRD)、透射电镜(TEM)、N₂吸附/脱附技术对样品晶相、形貌和比表面积进行了表征. 根据介孔α-Fe₂O₃悬浮液的酸碱滴定数据, 使用FITEQL软件, 采用双电层恒电容模型计算得出了介孔α-Fe₂O₃的表面酸碱反应平衡常数. 在此基础上研究了Cu^2＋, Pb^2＋, Zn^2＋在介孔氧化铁表面的吸附行为, 使用WinSGW软件模拟得出了相应的表面配合反应平衡常数并讨论了其吸附机理.     

酸法纳米纤维素模板剂合成介孔TiO2及光催化活性

以生物可再生资源的酸法纳米纤维素为模板剂,四氯化钛为钛源,采用液相水解-沉淀法制备了具有介孔结构的TiO2光催化剂。采用低温N2物理吸附-脱附、透射电镜(TEM)、X射线衍射(XRD)、热重-量热扫描(TG/DSC)、傅里叶变换红外(FTIR)、X射线光电子能谱(XPS)等对介孔TiO2进行了表征,并以甲基橙为模型物,考察了介孔TiO2光催化活性。结果表明,以酸法纳米纤维素为模板剂合成的TiO2光催化活性显著提高,且具有良好的孔隙结构,平均孔径5.03 nm、总孔容积0.35 cm3.g-1、比表面积192m2.g-1;纤维素模板剂合成的TiO2表面羟基数量降低;纤维素长链分子结构之间的羟基与TiO2表面羟基的键合,可有效限制TiO2前驱体的生长和团聚,并抑制锐钛矿相TiO2向金红石相转变。     

Synthesis,Characterization, and Sol-Gel Behavior of Dichlorotitanium(IV) (O-Alkyl,O-Cycloalkyl,and O-Aryl Trithiophosphates)

Dichlorotitanium(IV) trithiophosphates of the type TiCl₂[(RO)P(S)S₂] (where R = Me, Et, Prⁿ, Prⁱ, Buⁿ, Bu^s, Buⁱ, Amⁱ, Ph and cyclohexyl) have been synthesized for the first time by the reaction of titanium tetrachloride with potassium trithiophosphates in a 1:1 molar ratio in anhydrous benzene. Sol-gel chemistry of these titanium(IV) compounds has been studied in dry benzene by treatment with hydrogen sulfide gas. These newly synthesized derivatives have been characterized by elemental analysis (C, H, S, Cl, and Ti), molecular weight measurement, and spectral [IR and multinuclear NMR (¹H, ¹³C, and ³¹P)] studies. The bonding mode of trithiophosphate ligands and tentative structure around titanium(IV) are discussed.     

Functionalized SiO2 With S-Donor Thiophene: Synthesis,Characterization, and Its Heavy Metals Adsorption

Porous silica has been chemically modified with thiophene using the heterogeneous route. This synthetic route involved the reaction of native silica, SiO₂, with a commercial silylating agent, 3-glycidoxypropyltrimethoxysilane, followed by the immobilization of the thiophene chelating groups on the support. The resulting material has been characterized by thermogravimetry, FTIR spectra, and elemental analysis. The solid was also studied and evaluated by determination of the surface area using the BET equation, and the adsorption and desorption capability using the isotherm of nitrogen and B.J.H. pore sizes. The new synthesized material was employed in a batch method as adsorbent from aqueous solutions of Hg²⁺, Cd²⁺, Pb²⁺, Cu²⁺, Zn²⁺, K⁺, Na⁺, and Li⁺.     

A synthesis of porous activated carbon materials derived from vitamin B9 base for CO2 capture and conversion

CO₂ capture and conversion are still a favorable way to reduce CO₂ in the atmosphere. Herein, we have developed an environmentally friendly, low energy consumption porous activated carbon from vitamin B9 carbonaceous material for CO₂ capture and conversion materials. It is demonstrated that the KOH/vitamin B9 carbonaceous material impregnation ratio of 2 is the optimum condition for obtaining porous activated carbons with high specific surface area of 1903 m²g^-1, micropore surface area of 710 m²g^-1, total pore volume of 1.05 cm³g^-1 and micropore volume of 0.38 cm³g^-1. Among all the porous activated carbons prepared, the porous activated carbon synthesized with the KOH/vitamin B9 carbonaceous material impregnation ratio of 2 registers the most excellent CO₂ capture for 5.41 mmolg^?1 at 0 °C/1 bar and 3.66 mmolg^?1 at 25 °C/1 bar. They can also effectively catalyze the cycloaddition of CO₂ and epoxides under mild conditions (1 bar, 100 °C and 8 h) with a yield of 89–94%. The synthesized porous carbon materials from vitamin B9 is a promising candidate material for CO₂ capture and fixation.     

MnO2 Nanosheets Grown on Nitrogen‐Doped Hollow Carbon Shells as a High‐Performance Electrode for Asymmetric Supercapacitors

A hierarchical hollow hybrid composite, namely, MnO₂ nanosheets grown on nitrogen‐doped hollow carbon shells (NHCSs@MnO₂), was synthesized by a facile in situ growth process followed by calcination. The composite has a high surface area (251 m²g^?1) and mesopores (4.5 nm in diameter), which can efficiently facilitate transport during electrochemical cycling. Owing to the synergistic effect of NHCSs and MnO₂, the composite shows a high specific capacitance of 306 F g^?1, good rate capability, and an excellent cycling stability of 95.2 % after 5000 cycles at a high current density of 8 A g^?1. More importantly, an asymmetric supercapacitor (ASC) assembled by using NHCSs@MnO₂ and activated carbon as the positive and negative electrodes exhibits high specific capacitance (105.5 F g^?1 at 0.5 A g^?1 and 78.5 F g^?1 at 10 A g^?1) with excellent rate capability, achieves a maximum energy density of 43.9 Wh kg^?1 at a power density of 408 W kg^?1, and has high stability, whereby the ASC retains 81.4 % of its initial capacitance at a current density of 5 A g^?1 after 4000 cycles. Therefore, the NHCSs@MnO₂ electrode material is a promising candidate for future energy‐storage systems.     

Electrosurface characteristics of titanium dioxide in solutions of simple electrolytes: I. Effect of nature of counterions on adsorption and electrokinetic parameters of TiO<Subscript>2</Subscript>

The adsorption and electrokinetic characteristics of different titanium dioxide samples (produced by the Merck Co. and synthesized by the sol-gel method) are studied depending on the pH, background electrolyte concentration, and the nature of counterions (halide ions and Na⁺, K⁺, Ba²⁺, and La³⁺ metal ions). It is revealed that, in the presence of an indifferent electrolyte, the points of zero charge (PZC) for the synthesized TiO₂ sample and the Merck sample correspond to pH = 6.0 ± 0.1 and 5.0, respectively. It is found that the nature of halide ions has almost no influence on the magnitude of the TiO₂ surface charge σ₀ (in the region of its positive values) and the position of PZC. An increase in the specificity of cations with a rise in the charge causes PZC shift to the acidic region and enhances the absolute values of σ₀ at both negative and positive surface charges. It is established that the positions of PZC and isoelectric point in 10⁻² M solutions of the examined 1: 1 electrolytes nearly coincide with one another. The ζ potential is found to decline in the following series of counterions: Cl⁻, Br⁻, and I⁻ due to an increase in the degree of filling of the dense part of the electrical double layer.     

Influence of the support on the state of nickel in the Ni/SiO2, Ni/ZrO2, and Ni/SO4/ZrO2 oxide systems studied by diffuse-reflectance IR spectroscopy

The Ni/SiO₂, Ni/ZrO₂, and Ni/SO₄/ZrO₂ systems were studied by diffuse-reflectance IR spectroscopy using CO as a probe molecule. The Ni/SiO₂ and Ni/ZrO₂ systems are similar in properties, and the state of nickel in the Ni/ZrO₂ system is determined by the specific surface area. In the Ni/SO₄/ZrO₂ system, the surface sulfur compounds affect substantially the state of nickel: Ni^δ+ species with a partial positive charge are formed due to the strong electron-acceptor properties of the sulfur compounds. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 409–413, March, 1998.     

Synthesis and characterization of crystalline nanosized MgF2 powder via microemulsion route

Nanosized MgF₂ was synthesized by precipitation in microemulsions of water in cyclohexane stabilized by polyethylene glycol tert-octylphenyl ether. The synthesized MgF₂ powder was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), BET specific surface area, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray diffraction (XRD). The results showed that the synthesized powder was a MgF₂ powder with a crystallite size in the range of 9-11 nm and a specific surface area of 190 m²/g.     

Mesoporous Carbon Nanofibers Embedded with MoS2 Nanocrystals for Extraordinary Li‐Ion Storage

MoS₂ nanocrystals embedded in mesoporous carbon nanofibers are synthesized through an electrospinning process followed by calcination. The resultant nanofibers are 100–150 nm in diameter and constructed from MoS₂ nanocrystals with a lateral diameter of around 7 nm with specific surface areas of 135.9 m² g^?1. The MoS₂@C nanofibers are treated at 450 °C in H₂ and comparison samples annealed at 800 °C in N₂. The heat treatments are designed to achieve good crystallinity and desired mesoporous microstructure, resulting in enhanced electrochemical performance. The small amount of oxygen in the nanofibers annealed in H₂ contributes to obtaining a lower internal resistance, and thus, improving the conductivity. The results show that the nanofibers obtained at 450 °C in H₂ deliver an extraordinary capacity of 1022 mA h g^?1 and improved cyclic stability, with only 2.3 % capacity loss after 165 cycles at a current density of 100 mA g^?1, as well as an outstanding rate capability. The greatly improved kinetics and cycling stability of the mesoporous MoS₂@C nanofibers can be attributed to the crosslinked conductive carbon nanofibers, the large specific surface area, the good crystallinity of MoS₂, and the robust mesoporous microstructure. The resulting nanofiber electrodes, with short mass‐ and charge‐transport pathways, improved electrical conductivity, and large contact area exposed to electrolyte, permitting fast diffusional flux of Li ions, explains the improved kinetics of the interfacial charge‐transfer reaction and the diffusivity of the MoS₂@C mesoporous nanofibers. It is believed that the integration of MoS₂ nanocrystals and mesoporous carbon nanofibers may have a synergistic effect, giving a promising anode, and widening the applicability range into high performance and mass production in the Li‐ion battery market.