A sustainable printed circuit board derived hierarchically porous carbon/polyaniline composites for supercapacitors

The hierarchically porous carbon/polyaniline electrodes derived from the nonmetallic part of waste printed circuit board have been synthesized by a convenient carbonization and activation method. A detailed analysis of the morphology, structure, and electrochemical performances of as-prepared composites is presented. As expected, the balanced specific surface area and porous structure manifest their remarkable electrochemical performances. Apparently, the multiple synergistic effects are crucial to simultaneously achieving high capacity and significantly increased stability. As a result, the electrodes display exceptional rate capability, superior cyclic stability, and high specific capacitance (520.0 F/g at 1 A/g). Furthermore, the asymmetrical device possesses an improved energy density of 9.3 Wh/kg with a power density of 62.4 W/kg in H₂SO₄ electrolyte. Moreover, a potential mechanism contributing to the superior performance of hierarchically porous carbon/polyaniline composites has been studied in detail. Noteworthy, this study provides a feasible strategy for recycling waste printed circuit boards. Importantly, this approach will provide a path toward the rational synthesis and design of electrode materials for supercapacitors that take both high-performance and cost-effective into account.     

A novel “coral” carbon microprobe with and without N2 incorporation

“Coral”-type microstructure carbon films, with and without N₂ incorporation, were grown on sharpened tungsten microprobes by plasma enhanced chemical vapor deposition (PECVD) using H₂/CH₄/N₂ and H₂/CH₄ gas mixtures, respectively. The electrochemical behaviors of the coral-type carbon coated tungsten microprobe, characterized by various concentrations of ferrocyanide in a background of 0.1 M KCl, show excellent structural stability with similar microstructure before and after prolonged analysis without the need of surface pretreatment. The microprobes exhibit quasi-reversible kinetics with high signal-to-noise S/B ratio. The N₂ incorporated microprobe shows a slightly wider potential window, no surface adsorption of the analyte and higher sensitivity as compared to the sample without nitrogen incorporation. Furthermore, the wide potential window of  3 V is very good as compared to boron-doped diamond electrodes which are  3.5 V. This well behaved; broad electrochemical behavior and the simple fabrication method make the “coral” carbon film microprobe an excellent candidate for electrochemical sensing.     

Anisotropy investigation of cobalt ferrite nanoparticles embedded in polyvinyl alcohol matrix: A Monte Carlo study

The magnetic properties of the cobalt ferrite/polyvinyl alcohol nanocomposites have been studied experimentally and theoretically. For investigation the impact of polymeric matrix on magnetic properties of magnetic nanoparticles, four different processes have been considered for synthesizing the polymer based nanocomposites by co-precipitation method. The effective magnetic anisotropy obtained by Monte Carlo simulation and law of approach to the saturation magnetization showed a significant decrease relative to the bulk and bare cobalt ferrite nanoparticles. The polymeric matrix interacted with the surface of particles by different strength and made them approximately non-interacting. The as synthesized samples characterized by X-Ray diffractions (XRD) and Fourier transform infrared spectroscopy (FT-IR). Magnetic measurements were carried out at room temperature using a vibrating sample magnetometer (VSM).     

Encapsulation of manganese oxides nanocrystals in electrospun carbon nanofibers as free-standing electrode for supercapacitors

Flexible composites with manganese oxides (MnO_x) nanocrystals encapsulated in electropun carbon nanofibers were successfully fabricated via a simple and practical combination of electrospinning and carbonization process. The as-formed MnO_x/carbon nanofibers composites have a rough surface with MnO_x nanoparticles well embedded in the carbon nanofibers backbones. When used as electrodes for supercapacitor, the resulting MnO_x/carbon nanofiber composites exhibit good electrochemical performance with a specific capacitance of 174.8 F g⁻¹ at 2 mV s⁻¹ in 0.5 M Na₂SO₄ electrolyte, a good rate capability at high current density and long-term cycling stability. It is expected that such freestanding composites could be promising electrodes for high-performance supercapacitors.     

一氧化碳干燥技术及应用

本文阐述了光气生产中一氧化碳冷冻脱水-分子筛吸附的干燥技术,使得干燥后一氧化碳水份含量≤100ppm,提高了光气及光气化产品的质量和设备使用寿命,保证了光气安全生产。     

CO and CO2 hydrogenation study on supported cobalt Fischer–Tropsch synthesis catalysts

The conversion of CO/H₂, CO₂/H₂ and (CO+CO₂)/H₂ mixtures using cobalt catalysts under typical Fischer–Tropsch synthesis conditions has been carried out. The results show that in the presence of CO, CO₂ hydrogenation is slow. For the cases of only CO or only CO₂ hydrogenation, similar catalytic activities were obtained but the selectivities were very different. For CO hydrogenation, normal Fischer–Tropsch synthesis product distributions were observed with an of about 0.80; in contrast, the CO₂ hydrogenation products contained about 70% or more of methane. Thus, CO₂ and CO hydrogenation appears to follow different reaction pathways. The catalyst deactivates more rapidly for the conversion of CO than for CO₂ even though the H₂O/H₂ ratio is at least two times larger for the conversion of CO₂. Since the catalyst ages more slowly in the presence of the higher H₂O/H₂ conditions, it is concluded that water alone does not account for the deactivation and that there is a deactivation pathway that involves the assistance of CO.     

Layer-by-layer assembly of single-walled carbon nanotube-poly(viologen) derivative multilayers and their electrochemical properties

Layer-by-layer (LBL) multilayers of oxidized single-walled carbon nanotubes (SWCNTs) and poly(octylviologen) derivative (POV) have been assembled on gold electrode surfaces. The assembling process was characterized by quartz crystal microbalance (QCM) and electrochemical measurements. The average mass change was about 0.726 and 0.381 μg for each assembly of SWCNTs and POV, respectively. Cyclic voltammograms of the LBL multilayer modified electrodes showed well-reversible redox waves centered at about −640 mV vs Ag/AgCl, corresponding to the normal redox reaction of viologens. These LBL multilayers were very stable in the air and 1 mol/l KCl electrolyte solution. The results of QCM, cyclic voltammograms and chronocoulomograms of the multilayer modified Au electrodes indicated that the oxidized SWCNTs could not only support the formation of stable multilayers but also act as an electron mediator between viologens and electrodes.     

Studies of carbon monoxide and hydrogen adsorption on nickel and cobalt foils aimed at gaining a better insight into the mechanism of hydrocarbon formation

Systematic studies of adsorption of hydrogen and carbon monoxide on polycrystalline surfaces of nickel and cobalt have been carried out. The aim of these studies was to gain a better insight into the catalyzed formation of hydrocarbons from H₂-CO mixtures. We have studied the adsorption of these gases by means of thermal desorption spectroscopy (TDS) on nickel foils and powders. More recently, we have obtained desorption spectra of hydrogen adsorbed on cobalt foils and powders. In this work we described desorption spectra of carbon monoxide on cobalt foils. Carbon monoxide desorption from cobalt foils was studied in a similar way as prior work, using a mass spectrometric method in an ultra high vacuum system. Two carbon monoxide desorption peaks were observed. These two states correspond to molecular CO and presumably dissociated CO, as it is observed in the case of stepped surfaces of Ni and Co single crystals. An activation energy of around 4.0 kcal/mol is obtained for the molecular state while for the dissociated state the energy is coverage-dependent with a value between 8.0 and 15.0 kcal/mol. The carbon monoxide desorption peaks were fitted with near Gaussian curves which facilitates the analysis of the data to obtain activation energies for desorption. Kinetic parameters for carbon monoxide and hydrogen desorption from nickel and cobalt foils are provided and compared with already published data involving single crystals.     

Measuring oxygen, carbon monoxide and hydrogen sulfide diffusion coefficient and solubility in Nafion membranes

A Devanathan-Stachurski type diffusion cell made from a fuel cell assembly is designed to evaluate the gas transport properties of a proton exchange membrane as a function of cell temperature and gas pressure. Data obtained on this cell using the electrochemical monitoring technique (EMT) is used to estimate solubility and diffusion coefficient of oxygen (O₂), carbon monoxide (CO) and hydrogen sulfide (H₂S) in Nafion membranes. Membrane swelling and reverse-gas diffusion due to water flux are accounted for in the parameter estimation procedure. Permeability of all three gases was found to increase with temperature. The estimated activation energies for O₂, CO and H₂S diffusion in Nafion 112 are 12.58, 20 and 8.85 kJ mol⁻¹, respectively. The estimated enthalpies of mixing for O₂, CO and H₂S in Nafion 112 are 5.88, 3.74 and 7.61 kJ mol⁻¹, respectively. An extensive comparison of transport properties estimated in this study to those reported in the literature suggests good agreement. Oxygen permeability in Nafion 117 was measured as a function of gas pressures between 1 and 3 atm. Oxygen diffusion coefficient in Nafion 117 is invariant with pressure and the solubility increases with pressure and obeys Henry's law. The estimated Henry's constant is 3.5 × 10³ atm.     

一氧化碳吸附干燥器的技术改进

针对原吸附干燥器存在内部盘管焊接接头容易泄漏、设备使用寿命短、材质浪费较大等问题,对其进行了改进。将其中的气体分布改为筛孔板结构,在盘管和总管之间增加异径接头,在夹套与内筒之间增加加强圈,改进后的吸附干燥器结构合理,投资省,效率高,运行平稳。     

Oxygen vacancy-rich flower-like nickel cobalt layered double hydroxides for supercapacitors with ultrahigh capacity

One of the main difficulties for high-performance supercapacitors (SCs) is to design rational structures with excellent electrochemical properties. Herein, oxygen vacancy-rich nickel-cobalt layered double hydroxide, which has excellent supercapacitor performance, is prepared through an electrodeposition procedure and in situ oxidation process on nickel foam substrate. The conductivity and electrochemical properties are significantly improved by oxygen vacancies, which can be adjusted via hydrogen peroxide treatment. NiCo-LDH with oxygen vacancy (O_v-NiCo-LDH) attains a superior specific capacity of 1160 C g^?1 at the current density of 1 A g^?1 and shows a good capacity retention rate (61% of its original specific capacity is left at 20 A g^?1). Significantly, when the power density is 1.75 kW kg^?1, the energy density of the assembled symmetric supercapacitor (SSC) device is up to 216.19 Wh·kg^?1. This vacancy engineering strategy is helpful to the design of active materials for energy storage devices in the future.     

Hydrogenation of carbon monoxide under mechanical activation conditions

The work focuses on the hydrogenation of carbon monoxide over solid catalysts undergoing mechanical activation by ball milling. The rate of carbon monoxide conversion at individual ball impacts was estimated by measuring the impact frequency, the mass of powders involved in individual impacts and their duration. The rate of the mechanochemical hydrogenation process was compared with the one of the corresponding thermal process. An enhancement of the catalyst activity under mechanical activation conditions is observed.     

Thermal conductivity of carbon nanotubes and their polymer nanocomposites: A review

Thermally conductive polymer composites offer new possibilities for replacing metal parts in several applications, including power electronics, electric motors and generators, heat exchangers, etc., thanks to the polymer advantages such as light weight, corrosion resistance and ease of processing. Current interest to improve the thermal conductivity of polymers is focused on the selective addition of nanofillers with high thermal conductivity. Unusually high thermal conductivity makes carbon nanotube (CNT) the best promising candidate material for thermally conductive composites. However, the thermal conductivities of polymer/CNT nanocomposites are relatively low compared with expectations from the intrinsic thermal conductivity of CNTs. The challenge primarily comes from the large interfacial thermal resistance between the CNT and the surrounding polymer matrix, which hinders the transfer of phonon dominating heat conduction in polymer and CNT.This article reviews the status of worldwide research in the thermal conductivity of CNTs and their polymer nanocomposites. The dependence of thermal conductivity of nanotubes on the atomic structure, the tube size, the morphology, the defect and the purification is reviewed. The roles of particle/polymer and particle/particle interfaces on the thermal conductivity of polymer/CNT nanocomposites are discussed in detail, as well as the relationship between the thermal conductivity and the micro- and nano-structure of the composites.     

Facile synthesis of three dimensional flower-like Co3O4@MnO2 core-shell microspheres as high-performance electrode materials for supercapacitors

In this work, we reported the synthesis of three dimensional flower-like Co₃O₄@MnO₂ core-shell microspheres by a controllable two-step reaction. Flower-like Co₃O₄ microspheres cores were firstly built from the self-assembly of Co₃O₄ nanosheets, on which MnO₂ nanosheets shells were subsequently grown through the hydrothermal decomposition of KMnO₄. The MnO₂ nanosheets shells were found to increase the electrochemical active sites and allow faster redox reaction kinetics. Based on these advantages, when used as an electrode for supercapacitors, the prepared flower-like Co₃O₄@MnO₂ core-shell composite electrode demonstrated a significantly enhanced specific capacitance (671 F g⁻¹ at 1 A g⁻¹) as well as improved rate capability (84% retention at 10 A g⁻¹) compared with the pristine flower-like Co₃O₄ electrode. Moreover, the optimized asymmetric supercapacitor device based on the flower-like Co₃O₄@MnO₂//active carbon exhibited a high energy density of 34.1 W h kg⁻¹ at a power density of 750 W kg⁻¹, meaning its great potential application for energy storage devices.     

Carbon-ceramic composites from coal tar pitch and clays: application as electrocatalyst support

Carbon-ceramic composites have been prepared and characterised by different techniques (electron microscopy, X-ray microanalysis, X-ray diffraction and cyclic voltammetry). The effect on the conductivity of the thermal treatment temperature of the composites and the structure of the starting ceramic has been analysed. The results demonstrate that the layered structure of the clay determines their conductivity. The composites prepared are conductors and the conductivity goes through a maximum with increasing thermal treatment. Platinum has been successfully deposited on the carbon-ceramic composite by chemical and electrochemical methods. A better distribution of platinum and smaller particle sizes are obtained by the electrochemical method. The direct electrooxidation of methanol in acid medium has been studied on platinum-modified carbon-ceramic electrodes.     

Carbon aerogels derived from cresol–resorcinol–formaldehyde for supercapacitors

The objective of the present paper is to demonstrate the possibility to synthesize mixed carbon aerogels (denoted C_mRF) from cresol (C_m), resorcinol (R) and formaldehyde (F), as an alternative economic route to the classical RF synthesis. These porous carbon aerogels can be used as electrode materials for supercapacitors with a high volume-specific capacitance. Organic precursor gels were synthesized via polycondensation of a mixture of resorcinol and cresol with formaldehyde in an aqueous alkaline (NaOH) solution. After gelation and aging the solvent was removed via drying at ambient pressure to produce organic aerogels. Upon pyrolysis of the organic aerogels at 1173 K, monolithic carbon aerogels can be obtained. By controlling the catalyst (Cat) molar ratio (C_m+R/Cat) in the range 200–500, up to 70% of the resorcinol can be replaced with the cheap cresol. The resulting homogeneous organic aerogels exhibit a drying shrinkage below 15% (linear). The shrinkage and mass loss upon pyrolysis of the mixed aerogels increase with increasing cresol content. Nitrogen adsorption at 77 K was employed to characterize the microstructure of the carbon aerogels. The data show that the porous structure of mixed carbon aerogels is similar to that of RF carbon aerogels. Cyclic voltammetry measurements show that the as-prepared C_mRF carbon aerogels exhibit a high volume-specific capacitance of up to 77 F/cm³.     

Carbon nanotubes branch on cobalt oxide nanowires core as enhanced high-rate cathodes of alkaline batteries

Directional synthesis of carbon/metal oxide core-branch arrays is of great importance for development of advanced high-rate alkaline batteries. In this work, we report a facile hydrothermal-chemical vapor deposition (CVD) method for controllable fabrication of Co₃O₄ @CNTs core-branch arrays. Interestingly, free-standing Co₃O₄ core nanowires are intimately decorated by cocoon-like branch CNTs with diameters of 20–30?nm, which act as a highly conductive network and structure stabilizer. The electrochemical performance of the designed Co₃O₄ @CNTs core-branch arrays are tested as cathodes of alkaline batteries. Arising from enhanced electrical conductivity, larger surface area and improved structural stability, the Co₃O₄ @CNTs arrays show superior high-rate electrochemical performance with a higher capacity (116 mAh g^?1 at 2.5?A?g^?1), lower polarization and better cycling stability than the pure Co₃O₄ nanowires arrays (76 mAh g^?1 at 2.5?A?g^?1). Our directional composite strategy can be extended to preparation of other carbon-based core-branch arrays for applications in electrochemical batteries and catalysis.     

Synthesis and characterization of soluble multi-walled carbon nanotube/poly(organophosphazene) composites

Poor solubility of carbon nanotubes (CNTs) in water and organic solvents offers a significant problem for their applications. Macromolecules can be suitable solubilizing agents and a structural component of composite materials for CNTs. Several polymers were tested for the preparation of CNT dispersions. In this study, a poly[(4-pyridineoxy)(phenoxy)phosphazene] (3) was prepared by sequential treatment of poly(dichlorophosphazene) (2) with sodium 4-pyridineoxy and sodium phenoxide in THF. Multi-walled carbon nanotube/poly(organophosphazene) composites (f-MWCNT/PZS) with different feed ratios [R_feed = 1:1, 1:3, 1:5 and 1:10 (w/w)] were obtained by the treatment of the functionalized multi-walled carbon nanotube (f-MWCNT) with the protonated poly(organophosphazene) (PZS). Excellent dispersions of the f-MWCNT/PZS nanocomposites in water and common organic solvents were achieved. The influence of feed ratio on polymer coating and the stability of composites were investigated by thermal gravimetric analysis (TGA). f-MWCNT/PZS_1:5 nanocomposite was characterized by ³¹P, ¹H NMR, FTIR, XRD, EDX and Raman Spectroscopy. The morphologic characterizations of f-MWCNT/PZS_1:5 were carried out by HRTEM and SEM methods.     

Effects of preparation methods on the properties of cobalt/carbon catalyst for methane reforming with carbon dioxide to syngas

The effect of different preparation methods on the physicochemical property, reforming reactivity, stability and carbon deposition resistance of cobalt/carbon catalyst was investigated through fixed bed flow reaction. The catalysts were prepared by the impregnation and characterized by the XRD and scanning electron microscopy (SEM). The result indicated that the active components of cobalt/carbon catalyst prepared by using ultrasonic wave distributed evenly, activity was high and the loading time was short. The Co/Carbon catalyst prepared by incipient-wetness impregnation, 10 wt% loading and 300 °C calcination, achieved the best activity. Furthermore, the effect of reaction temperature, air speed and CH₄/CO₂ ratio on the catalyst activity and CO/H₂ ratio in products was investigated. It was found that the conversion of CO₂ and CH₄ increased with the increasing of reaction temperature. However, the conversion of CO₂ and CH₄ increased first and then decreased with the increasing of air speed. With the increasing of CH₄/CO₂ in feed gas, both the catalyst activity and the CO/H₂ ratio in products decreased.