Binder-free,self-standing films of iron oxide nanoparticles deposited on ionic liquid functionalized carbon nanotubes for lithium-ion battery anodes

We report in-situ synthesis and direct deposition of Fe₂O₃ nanoparticles (NPs) on the ionic liquid (IL)-functionalized carbon nanotubes (fCNT). As shown in transmission electron microscope (TEM) and scanning TEM (STEM) images, Fe₂O₃ NPs with the diameter of 3–5 nm are randomly distributed on the sidewall of fCNT, revealing the nanocrystalline structure. The chemical identity and interaction of the fCNT/Fe₂O₃ composite are investigated by FT-IR, Raman and XPS analyses. In particular, the fCNT/Fe₂O₃ composite is solution-processable in a form of binder free and self-standing film. Such a free-standing electrode film based on the fCNT/Fe₂O₃ composite achieve the discharge capacity of 413 mAh g⁻¹ which is much greater than 34 mAh g⁻¹ of the CNT and 191 mAh g⁻¹ of the fCNT due to the redox reaction of Fe₂O₃ NPs. Moreover, the fCNT/Fe₂O₃ composite show the coulombic efficiency of 98% and the capacity fading from 272 mAh g⁻¹ to 182 mAh g⁻¹ after 50 cycles of charge/discharge.     

Facile synthesis of MOF-5 structure with large surface area in the presence of benzoyl peroxide by room temperature synthesis

In this study, for the first time, the uniform cylindrical MOF-5-BPO (Zn₄O(BDC)₃(H₂O)·0.5ZnO, BDC = 1,4-benzenedicarboxylate, BPO = benzoyl peroxide) crystals with large Brunauer–Emmett–Teller (BET) surface area (3210.2 m² g⁻¹) was successfully synthesized by room temperature synthesis in the presence of BPO using zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O) as the zinc source. The pore volumes of MOF-5-BPO materials prepared with different concentrations of BPO were 0.84–1.07 cm³ g⁻¹, higher than that of MOF-5-NP (0.68 cm³ g⁻¹, Zn₄O(BDC)₃(H₂O)₃·2ZnO) and MOF-5-H₂O₂ (0.84 cm³ g⁻¹, Zn₄O(BDC)₃(H₂O)₂·2ZnO, H₂O₂ = hydrogen peroxide). The addition of the peroxides created new pores, which possessed the same diameters as the existing ones, thus increased the pore volume of the product. The concentration of BPO was critical for the pore texture of MOF-5-BPO. Moreover, MOF-5-BPO could store 1.24 wt% hydrogen at 77 K and 100 kPa. Thus, this study points out some information for one to realize the influence of the peroxides over MOF-5 structure and promises the potentiality of large-scale production of MOF-5 structure with large surface area.     

Anion-exchange properties of nickel–aluminum layered double hydroxide prepared by liquid phase deposition

The optimum coordination structure of Ni–fluoro complexes for the preparation of Ni–Al LDH by LPD process and the diverse anion-exchange properties of as-deposited Ni–Al on α-alumina powder were quantitatively evaluated for the industrial application of new positive material for alkali secondary batteries. The [NiF_6−x−y(NH₃)_x(OH⁻)_y]ⁿ⁺ was more suitable than [NiF₆]⁴⁻ as the precursor of the deposition of Ni–Al LDH in the LPD reaction, and the improved LPD reaction achieved the synthesis of high purity and high crystallinity Ni–Al LDH. All anion-exchanged Ni–Al LDHs for OH⁻–, Cl⁻–, SO₄²⁻–, and CH₃COO⁻–forms kept the high crystallinity and showed the enlargement of interlayer distances. The tilting angle of the intercalated CH₃COO⁻ anions was about 15°. Anion-exchange capacity remained constant at a minimum of 0.8 meq g⁻¹ in pH >10, increased as pH decreased, and reached a maximum of 8 meq g⁻¹ at pH 2. Anion-exchange of OH⁻–form of Ni–Al LDH was accelerated by the neutralization of hydroxide ions in interlayers, in addition, the anion-exchange capacity and the crystallinity of Ni–Al LDH could be controlled by the amount of doped aluminum ions.     

Synthesis of LiNi0.9Co0.1O2 cathode material for lithium secondary battery by a novel route

The cathode material, LiNi_0.9Co_0.1O₂ was prepared using a rheological phase reaction method with LiOH·H₂O, home-made Ni(OH)₂, and Co₂O₃ as starting materials. At first, the mixture of reactants and a proper amount of water reacted to form a rheological precursor. Then the dried precursor was heated at 730 °C in one step to yield the product. The effects of calcination time (between 0.5 and 10 h) on the structural, morphological and electrochemical properties were investigated. All obtained powders show a single phase with α-NaFeO₂ structure (R-3m space group). The sample prepared in 2.5 h delivers the largest initial discharge capacity of 218 mA h g^− 1 (3.0-4.35 V, 25 mA g^− 1) and still remains 192 mA h g^− 1 after 15 cycles. The method is simple, economical and effective and is promising for practical application.     

Superhydrophobic sodium silicate based silica aerogel prepared by ambient pressure drying

The superhydrophobic silica aerogel was prepared by using less expensive sodium silicate as a main silica source through a cost-effective and simple route via ambient pressure drying. The sodium impurity was first eliminated by mixing sodium silicate with a co-precursor methyltriethoxysilane (MTES) followed by ion exchange process. The hydrogel was formed by gelation and the alcogel was further obtained by alcoholization of the hydrogel. The surface of alcogel was modified by reacting with trimethylchlorosilane (TMCS) diluted in n-hexane. It was suggested that MTES accelerated water expelling from the hydrogel, while TMCS modified the surface of silica network by replacing Si–OH with Si–C. As a result, the obtained silica aerogel exhibited excellent physical properties with less than 10% volume shrinkage. The density, surface area and cumulative pore volume were 0.12 g cm⁻³, 684.44 m² g⁻¹, and 3.55 cm³ g⁻¹, respectively. The optical transmission reached 82.8% with the water contact angle of 146°.     

Influence of fineness of fly ash on the aggregate pelletization process

One of the main issues associated with fly ash is the variation in the fineness of fly ash produced within a plant and between thermal power plants, due to the variation in the quality of coal used and the production technique adopted in which pelletization of fly ash becomes complex. In this paper, the influence of fineness of fly ash is studied by collecting typical samples of fly ash from two thermal power plants. Significance of the factors influencing the pelletization of fly ash was statistically determined by adopting 2⁴ with eight run and 2⁵ with sixteen run fractional factorial design for fly ash with fineness of 414 m²/kg and 257 m²/kg, respectively. Finer fly ash exhibits higher pelletization efficiency as compared to coarser fly ash. Addition of clay binders like bentonite and kaolinite enhanced the pelletization efficiency of coarser fly ash. Amount of binder content and moisture content varies with type of binder used (with fly ash having a fineness of 257 m²/kg), which is attributed to the difference in plasticity index. Addition of clay binder changes the relative influence of pelletization factors.     

One-pot synthetic method to prepare highly N-doped nanoporous carbons for CO2 adsorption

A one-pot synthetic method was used for the preparation of nanoporous carbon containing nitrogen from polypyrrole (PPY) using NaOH as the activated agent. The activation process was carried out under set conditions (NaOH/PPY = 2 and NaOH/PPY = 4) at different temperatures in 600–900 °C for 2 h. The effect of the activation conditions on the pore structure, surface functional groups and CO₂ adsorption capacities of the prepared N-doped activated carbons was examined. The carbon was analyzed by X-ray photoelectron spectroscopy (XPS), N2/77 K full isotherms, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The CO₂ adsorption capacity of the N-doped activated carbon was measured at 298 K and 1 bar. By dissolving the activation agents, the N-doped activated carbon exhibited high specific surface areas (755–2169 m² g⁻¹) and high pore volumes (0.394–1.591 cm³ g⁻¹). In addition, the N-doped activated carbons contained a high N content at lower activation temperatures (7.05 wt.%). The N-doped activated carbons showed a very high CO₂ adsorption capacity of 177 mg g⁻¹ at 298 K and 1 bar. The CO₂ adsorption capacity was found to be dependent on the microporosity and N contents.     

Facile preparation and enhanced photocatalytic H2-production activity of Cu(OH)2 nanospheres modified porous g-C3N4

A facile precipitation approach for the preparation of Cu(OH)₂/g-C₃N₄ composite photocatalysts with good porous structure was developed for the first time. The as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible light (UV–vis) absorbance spectra, photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS). A photocatalytic water splitting reaction on the as-prepared photocatalysts were carried out under visible light irradiation. The results revealed that the prepared samples showed significantly enhanced photocatalytic activity. The optimal Cu(OH)₂ loading content was found to be 0.34 mol%, giving an H₂-production rate of 48.7 μmol h⁻¹ g⁻¹, which is higher 16.5 times than that of pure g-C₃N₄. This high photocatalytic H₂-production activity is attributed to the presence of Cu(OH)₂ clusters on the surface of the porous g-C₃N₄, which efficiently promotes the visible light absorption and separation of photogenerated electron–hole pairs.     

Template-free solvothermal synthesis of hierarchical boehmite hollow microspheres with strong affinity toward organic pollutants in water

Three-dimensional hierarchical boehmite hollow microspheres with a very high yield at low cost were successfully synthesized via a one-pot template-free solvothermal route using aluminum chloride hexahydrate as precursor in a mixed ethanol–water solution with assistance of trisodium citrate. The as-synthesized products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption/desorption techniques. The results show that Cl⁻ and addition amount of trisodium citrate have significant effect on the morphologies of the resultant products, and 6–8 mmol of trisodium citrate is optimal for the synthesis of boehmite hollow microspheres assembled from randomly interconnecting and aligned nanorods with solvothermal time no less than 15 h. A synergistic mediation mechanism of citrate ions and Cl⁻ to form boehmite hollow spheres via self-assembly morphology evolution was proposed based on the experimental results. Interestingly, the typical boehmite hollow microspheres with a surface area of 102 m² g⁻¹, pore volume of 0.37 cm3 g⁻¹, and the average pore size of 14.6 nm show superb adsorption properties for Congo red with maximum capacity of 114.7 mg g⁻¹ which is higher than that of a commercial boehmite. This simple synthetic route is a very promising way for the design and synthesis of new functional hierarchical nanostructured materials with desired adsorptive properties.     

Magnetic properties and methylene blue adsorptive performance of CoFe2O4/activated carbon nanocomposites

Owing to the unique microporous structure and high specific surface area, activated carbon (AC) could act as a good carrier for functional materials. In this paper, CoFe₂O₄/AC nanocomposites were prepared by a facile hydrothermal method for the adsorption of dyes in wastewater. The results indicated that CoFe₂O₄ nanoparticles presented the spinel structure and existed in the pores of AC. The saturation magnetization (Ms) increased with the CoFe₂O₄ content, while the surface area and pore volume decreased. For the larger magnetic moment, very few CoFe₂O₄ were needed to maintain the higher surface area of CoFe₂O₄/AC nanocomposites. The sample-5 (CoFe₂O₄:C = 1:200) possessed the surface area of 1096.85 m² g⁻¹ (close to 1243.35 m² g⁻¹ of AC) and Ms of 5.11 emu g⁻¹, which were sufficient for magnetic separation in wastewater treatment. 99% methylene blue could be adsorbed in 50 min, and then the CoFe₂O₄/AC nanocomposites could be separated from the solution easily by an outer magnet.     

Room temperature ferromagnetism in Zn0.99La0.01O and pure ZnO nanoparticles

Room temperature ferromagnetism (RTFM) was observed in both La-doped and pure ZnO nanoparticles synthesized by the sol–gel method. RTFM is intrinsic according to the results of X-ray diffraction and X-ray photoelectron spectroscopy. The saturation magnetization (M_S), the remnant magnetization at zero field and coercive field are 5 × 10⁻³, 7 × 10⁻⁴ emu g⁻¹, 100 Oe for Zn_0.99La_0.01O nanoparticles and 1.5 × 10⁻⁴, 1 × 10⁻⁵ emu g⁻¹, 50 Oe for pure ZnO nanoparticles, respectively. The magnetization is enhanced greatly by doping of La. Furthermore, the M_S of Zn_0.99La_0.01O nanoparticles decreases from 0.005 to 0.001 emu g⁻¹ as the annealing temperature increases from 500 to 700 °C. The doping of La introduces more oxygen vacancies into ZnO. The decrease of annealing temperature also produces more oxygen vacancies in La-doped ZnO. These results indicate that the origin of the RTFM is related to oxygen vacancies.     

Preparation and electrochemical properties of Cr doped LiV3O8 cathode for lithium ion batteries

Chromium was incorporated into lithium trivanadate by an aqueous reaction followed by heating at 100 °C. This Cr doped LiV₃O₈ as a cathode for lithium ion batteries exhibits 269.9 mAh g^− 1 at first discharge cycle and remains 254.8 mAh g^− 1 at cycle 100, with a charge-discharge current density of 150 mA g^− 1 in the voltage range of 1.8-4.0 V. The Cr-LiV₃O₈ cathode show excellent discharge capacity, with the retention of 94.4% after 100 cycles. These result values are higher than previous reports indicating that Cr-LiV₃O₈ prepared by our low temperature synthesis method is a promising cathode material for rechargeable lithium ion batteries. The enhanced discharge capacity and cycle stability of Cr-LiV₃O₈ cathode indicate that chromium atoms promote lithium transfer or intercalation/deintercalation during the electrochemical cycles and improve the electrochemical performances of LiV₃O₈ cathode.     

Preparation and surface properties of mesoporous silica particles modified with poly(N-vinyl-2-pyrrolidone) as a potential adsorbent for bilirubin removal

The surface of silica particles was modified with polyvinyl pyrrolidone (PVP) through sol–gel process. The different experimental techniques, i.e., thermogravimetric analysis (TGA and DTG), nitrogen adsorption, scanning electron microscopy (SEM), laser diffraction analysis (LDA), fourier transform spectroscopy (FTIR) are used to characterize the pure non-functionalized and functionalized silicas containing different amount of PVP. It was shown that PVP-modified silica samples have well developed porous structure; the values of specific surface area for PVP-modified silicas are in the range of 140–264 m² g⁻¹. While the non-functionalized silica shows the low surface area (S_BET = 40 m² g⁻¹). The BJH analysis showed that PVP can be used as an effective agent to increase an average pore size and total pore volume. The results indicate that PVP functionalized silicas show a potential as effective adsorbents for bilirubin removal compared to other available adsorbents.     

Electrochemical performance of the chalcopyrite CuFeS2 as cathode for lithium ion battery

Chalcopyrite CuFeS₂ was synthesized by solvothermal process. It was used as active species to prepare cathode of lithium ion batteries together with some conducting materials. Electrochemical performance of the assembled Li/CuFeS₂ batteries was characterized by cyclic voltammetry and discharging test. Our results proved that CuFeS₂ as a new cathode material showed room-temperature specific discharging capacity of 1100 mAh g⁻¹ at a current density of 14 mA g⁻¹, and that its specific discharging capacity was higher than 500 mAh g⁻¹ at a current density of 350 mA g⁻¹. Different from what reported by Eda et al., the discharging curves presented two apparent plateaus, which were related to different cathode reactions, in the whole measured temperature range.     

Conductive polyaniline capped Fe2O3 composite anode for high rate lithium ion batteries

A composite of Fe₂O₃ capped by conductive polyaniline (PANI) was synthesized by a facile two-step method through combining homogeneous Fe₂O₃ suspension prepared by a hydrothermal method and in-situ polymerization of aniline. As anode material for lithium ion batteries, the Fe₂O₃/PANI composite manifests very large discharge capacities of 1635 mAh g⁻¹, 1480 mAh g⁻¹ at large currents of 1.0 and 2.0 A g⁻¹ (1C and 2C), respectively, as well as good cycling performance and rate capacity. The enhancement of electrochemical performance is attributed to the improved electrical conductivity and effective ion transportation of the composite electrode, in that, PANI keeps the Fe₂O₃ nanorods uniformly connected and offers conductive contact between the electrolyte and the active electrode materials.     

Photoluminescence and magnetic properties of β-Ni(OH)2 nanoplates and NiO nanostructures

Single-crystalline β-nickel hydroxide (β-Ni(OH)₂) nanoplates of hexagonal structure have been synthesized through hydrothermal process. The β-Ni(OH)₂ nanoplates possess well-defined hexagonal shapes with landscape dimension of 45–140 nm and thickness of 20–50 nm. Post-thermal decomposition of the β-Ni(OH)₂ nanoplates led to the formation of single-crystalline NiO nanostructures with landscape dimension of 25–120 nm including nanorolls, nanotroughs and nanoplates. The sizes of the central hole in NiO nanorolls and the low-lying ground in NiO nanotroughs are in the range of 10–24 nm. Two photoluminescence emission peaks appear at 390.5 nm and 467 nm in the photoluminescence spectrum of NiO nanostructures and were assigned to the ¹T_{1 g} (G) → ³A_{2 g} and ¹T_{2 g} (D) → ³A_{2 g} transitions of Ni²⁺ in oxygen octahedral sites, respectively. Temperature-dependent magnetic measurement results show that an antiferromagnetic-paramagnetic transition occur at 26.3 K in β-Ni(OH)₂ nanoplates.     

Stability,electrochemical behaviors and electronic structures of iron hydroxyl-phosphate

Iron hydroxyl-phosphate with a uniform spherical particle size of around 1 μm, a compound of the type Fe_2−y□_y(PO₄)(OH)_3−3y(H₂O)_3y−2 (where □ represents a vacancy), has been synthesized by hydrothermal methods. The particles are composed of spheres of diameter <100 nm. The compound exhibits good electrochemical performance, with reversible capacities of around 150 mAh g⁻¹ and 120 mAh g⁻¹ at current densities of 170 mA g⁻¹ and 680 mA g⁻¹, respectively. The stability of crystal structure of this material was studied by TGA and XRD which show that the material remains stable at least up to the temperature 200 °C. Investigation of the electronic structure of the iron hydroxyl-phosphate by GGA + U calculation has indicated that it has a better electronic conductivity than LiFePO₄.     

Identification of admixture for pelletization and strength enhancement of sintered coal pond ash aggregate through statistically designed experiments

Statistically designed experiments using Response Surface Methodology have been undertaken to identify the parameters influencing manufacturing process and properties of aggregate using coal pond ash (generated from bituminous and lignite coal sources). Based on the preliminary studies, Ca(OH)₂ and borax have been identified as pelletization and strength enhancing admixture respectively. Pelletization efficiency of bituminous and lignite pond ash increased with an increase in binder and Ca(OH)₂ dosage to 20–98% and 50–98% respectively, with proportionate quantity of water. Sintering has been used as a hardening method with temperature range of 900 °C and 1100 °C for a duration range of 45–120 min. Phase composition and sintered microstructure of aggregate has been reported using X-ray diffraction and scanning electron microscopy respectively. The ten percent fines value of aggregate with clay binder was 5.5 tonne as against a value of 4.5 tonne with aggregate with bentonite binder. Among the binders studied, bentonite resulted in high volume utilization of pond ash, i.e. up to 88%.     

Morphologies and electrochemical properties of 0.6Li2MnO3·0.4LiCoO2 composite cathode powders prepared by spray pyrolysis

Nanosized 0.6Li₂MnO₃·0.4LiCoO₂ composite cathode powders are prepared by spray pyrolysis. The micron-sized composite powders are converted into nanosized powders by a simple milling process. The mean sizes of the composite powders measured from the TEM images increase from 20 to 170 nm when the post-treatment temperatures increase from 650 to 900 °C. The Brunauer–Emmett–Teller surface areas of the composite powders post-treated at 650 and 900 °C are 24 and 3 m² g⁻¹, respectively. The XRD patterns indicate that the layered composite powders post-treated at 800 and 900 °C have high crystallinity and low cation mixing. The mean crystallite sizes of the powders, measured from the (003) peak widths of the XRD patterns using Scherrer's equation, are 35 and 56 nm at post-treatment temperatures of 800 and 900 °C, respectively. The initial discharge capacities of the 0.6Li₂MnO₃·0.4LiCoO₂ composite are 262, 267, 264, and 263 mAh g⁻¹ when the post-treat temperatures of the powders are 650, 700, 800, and 900 °C, respectively. The discharge capacity of the composite powders post-treated at 900 °C abruptly decreases from 263 to 214 mAh g⁻¹ by the seventh cycle and then slowly decreases to 198 mAh g⁻¹ with increasing cycle number, up to 30.