Cathodic electrosynthesis of CuFe<Subscript>2</Subscript>O<Subscript>4</Subscript>/CuO composite nanostructures for high performance supercapacitor applications

In this work, CuFe₂O₄/CuO nanocomposites have been synthesized by galvanostatic cathodic electrodeposition. The obtained nanocomposites were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, Fourier Transform Infrared, and Brunauer–Emmett–Teller surface area analysis. The electrochemical properties of CuFe₂O₄/CuO nanocomposites were evaluated by cyclic voltammetry, galvanostatic charge–discharge cycling, and electrochemical impedance spectroscopy in 1.0 M KOH. The CuFe₂O₄/CuO nanocomposites have shown the high specific capacitance of 322.49 F g^?1 at the scan rate of 1 mV s^?1. After 5000 cycles, 92% of this specific capacitance was retained. Although the prepared nanocomposite has shown a mediocre specific capacitance compared to other metal oxide-based materials, the low cost of the starting materials and the ease of preparation make this nanocomposite a good candidate for supercapacitor applications.     

Synthesis of barium titanate nanoparticles via a novel electrochemical route

An electrochemical route from Ti metal plate in KOH and Ba(OH)₂ electrolyte at room temperature is first established for the synthesis of BaTiO₃ nanoparticles. Anodic sparks play a key role, and KOH concentration is one of the most significant factors which affect the appearance of anodic sparks in this method. XRD patterns show that the powder obtained in our study is a pure perovskite phase BaTiO₃ with a cubic structure, whose size and morphology are subsequently studied by TEM. The mean diameter of the particles is 13.8 nm and the standard deviation (S.D.) fitted is 6.26 nm. It is also found that the mean size of the obtained nanoparticles increase from 13.8 nm to 168.0 nm, when 60 vol.% absolute ethanol is replaced by distilled water as the solvent of the electrolyte.     

Preparation,characterization and catalytic behavior of copper oxide nanoparticles on thermal decomposition of ammonium perchlorate particles

In this study, copper oxide nanoparticles (CuO NPs) with mean particle size of 43–32?nm were prepared by wet grinding of commercial micronized CuO powders in a high-energy wet ball-milling apparatus during 20 and 30?h, respectively. X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM) analyses were used to characterize the structure, mean particle size and morphology of the resulting CuO NPs. The results confirmed that the CuO NPs obtained at different milling times consist of nanostructures with nearly spherical morphology and by increasing the milling time, smaller particle size was obtained. The catalytic activities of the synthesized CuO NPs on the thermal decomposition of ammonium perchlorate (AP) particles were examined through differential scanning calorimetry and thermogravimetry (DSC/TG) analyses. Evaluation of the experimental results illustrated that the surfaces of CuO NPs were effectively coated with AP particles and by adding 5%CuO NPs with 32?nm, the thermal decomposition temperature of the treated particles reduced by 83.0°C and the heat of decomposition reached 1553.7?Jg^?1. Moreover, the kinetic and thermodynamic parameters of the thermal decomposition of pure and AP?+?5%CW30 nanocomposites have been investigated by using the Kissinger, Boswell and Ozawa methods.     

活化剂对焦煤基多孔碳制备的影响及其在锂硫电池中的应用

煤炭作为一种来源广泛的非金属矿物,是制备大量多孔碳的理想原料。本文以1/3焦煤为原料,NaOH和KOH为活化剂,制备了多孔碳,并研究了硫/多孔碳复合正极材料的电化学性能。结果表明:采用NaOH和KOH单独活化时制备的多孔碳比表面积很大,分别为1 649 m2/g和1 867 m2/g,而采用NaOH和KOH混合活化制备的多孔碳比表面积大幅度下降,当NaOH与KOH质量比为1:1活化时多孔碳的比表面积最小,为290 m2/g。电化学测试表明,NaOH与KOH质量比为1:1混合活化的硫/多孔碳正极材料的电性能优于NaOH和KOH单独活化的硫/多孔碳正极材料,0.2 C下首次放电比容量为790 mA·h/g,库仑效率为93.16%,100次循环后放电比容量为740 mA·h/g。还分析讨论了煤基多孔碳孔径分布对电化学性能的影响。      

Electrochemical bulk synthesis and characterisation of hexagonal-shaped CuO nanoparticles

A simple and efficient two-step hybrid electrochemical–thermal route was developed for the bulk synthesis of CuO nanoparticles using aqueous sodium nitrate electrolyte and Cu electrodes in an undivided cell under galvanostatic mode at room temperature. The influence of electrolyte concentration on the synthesis of CuO nanoparticles was studied at 1.0?A/dm² current density. Electrochemically generated precursor was calcined for an hour at different levels of temperature in the range 200–900°C. The calcined samples were characterised by XRD, TG-DTA, XPS, SEM/EDAX, TEM, FT-IR and UV–Vis spectral methods. The crystallite sizes were estimated and the thermal behaviour of as-prepared compound was examined. Rietveld refinement of X-ray data shows results matching the monoclinic structure with the space group of C2/c (no. 15). The TEM result revealed that the particle sizes were in the order of 30–50?nm diameter and 120–200?nm length. The blue shift was noticed in UV–Vis absorption spectra. All samples of CuO exhibited randomly oriented hexagonal morphology.     

Preparation and electrochemical performance of alpha-nickel hydroxide nanowire

Alpha-nickel hydroxide nanowire with diameter of 60 nm was successfully synthesized by conversely migrates technique. Structural and morphological characterizations were performed using power X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The capacitive properties were evaluated by cyclic voltammetry (CV), galvanostatic charge–discharge and electrochemical impedance spectroscopy technique in 6 M KOH aqueous electrolyte. A maximum specific capacitance of 833 F g⁻¹ was obtained at constant current of 5 mA, indicating that the α-nickel hydroxide nanowire is a promising electrode material for electrochemical capacitors.     

A two-step method for synthesis of micron sized nanoporous silver powder and ZnO nanoparticles

Micron-sized nanoporous silver powder with pore size of ～100–160 nm and specific surface area of ～4.7–5.5 m²/g was synthesized from three mechanically alloyed Ag-Zn powders (composition: 25, 50 and 75 at.% Zn). Dealloying was carried out at free corrosion conditions in NaOH, HCl and AgNO₃ solutions. Both partial and complete dealloying were obtained by suitable choice of electrolyte and time of exposure. Zn in the solution after dealloying was recovered in the form of ZnO nanoparticles with particle size of 55.7 ± 18 nm. The effect of composition and electrolyte on the degree of dealloying was also studied.     

The effect of cysteine on electrodeposition of gold nanoparticle

The most applications of gold nanoparticles are in the photo-electronical accessories and bio-chemical sensors. Chloride solution with cysteine additive was used as electrolyte in gold nanoparticles electrodeposition. The nucleation and growing mechanism were studied by electrochemical techniques such as cyclic voltammetry and chronoamperometry, in order to obtain a suitable nano structure. The deposition mechanism was determined as instantaneous nucleation and the dimension of particles was controlled in nanometric particle size range. Atomic Force Microscope was used to evaluate the effect of cysteine on the morphology and topography of gold nanoparticles. Finally the catalytic property of gold nanoparticle electrodeposited was studied in KOH solution, where oxygen reduction on the gold nanoparticle surface was eight times greater than that on the conventional gold deposits.     

利用核桃壳制备高比表面积活性炭电极材料的研究

以核桃壳为原料,采用KOH活化法制备活性炭,并将其用作超级电容器电极材料。利用N2吸附和扫描电镜(SEM)表征活性炭的孔结构及表面形貌,系统研究碱炭比(KOH与核桃壳炭化料的质量比)对活性炭孔结构的影响,并采用恒流充放电及循环伏安等测定核桃壳活性炭电极材料在3mol/L KOH电解液中的电化学性能。结果表明,随着碱炭比的增大,活性炭的比表面积、总孔容及中孔比例先逐渐增大后稍有减小。当活化温度为800℃,活化时间为1h,碱炭比为4时,可制备出比表面积为2404m2/g,总孔容为1.344cm3/g,中孔比例为28.6%,孔径分布在0.7~3.0nm之间的高比表面积活性炭。该活性炭用作超级电容器电极材料具有良好的大电流放电特性和优异的循环性能,电流密度由50mA/g提高到5000mA/g时,其比电容由340F/g降低到288F/g,经1000次循环后,比电容保持率为93.4%。     

Sodium gluconate-assisted hydrothermal synthesis,characterization and electrochemical performance of LiFePO4 powders

Nano- and micro-sized LiFePO₄ powders were synthesized by a sodium gluconate (C₆H₁₁NaO₇)-assisted hydrothermal synthesis method at 220 °C for 10 h with pH = 2–7. The resulting powders were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy-dispersive X-ray spectrometer (EDS). The obtained data showed that the pH of synthesis solution played a key role in the formation of the LiFePO₄ powders with different morphologies, such as ball-like microspheres, irregular microspheres with the agglomerated rods and particles, sphere-like nanoparticles and nano-ellipsoids. The results from electrochemical performance measurements revealed that the charge–discharge cycling characteristics of the samples were strongly dependent on their morphologies. In particular, the ellipsoidal LiFePO₄ nanoparticles with the average size of 70–90 nm showed the highest initial discharge capacity of 150 mA h g⁻¹ at 0.1 C rate, and cycling stability of the ellipsoidal LiFePO₄ nanoparticles was optimum among all the samples prepared due to their dual advantages of high tap density and good diffusion property. The present study offers a simple morphology-controllable route, without carbon coating or doping with supervalent cations, to synthesize and to design high performance cathode materials for lithium-ion batteries.     

Samarium-doped Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles with improved magnetic and supercapacitive performance: a novel preparation strategy and characterization

Sm³⁺-doped magnetite (Fe₃O₄) nanoparticles were synthesized through a one-pot facile electrochemical method. In this method, products were electrodeposited on a stainless steel (316L) cathode from an additive-free 0.005 M Fe(NO₃)₃/FeCl₂/SmCl₃ aqueous electrolyte. The structural characterizations through X-ray diffraction, field-emission electron microscopy, and energy-dispersive X-ray indicated that the deposited material has Sm³⁺-doped magnetite particles with average size of 20 nm. Magnetic analysis by VSM revealed the superparamagnetic nature of the prepared nanoparticles (Ms = 41.89 emu g^?1, Mr = 0.12 emu g^?1, and H _Ci = 2.24 G). The supercapacitive capability evaluation of the prepared magnetite nanoparticles through cyclic voltammetry and galvanostat charge–discharge showed that these materials are capable to deliver specific capacitances as high as 207 F g^?1 (at 0.5 A g^?1) and 145 F g^?1 (at 2 A g^?1), and capacity retentions of 94.5 and 84.6% after 2000 cycling at 0.5 and 1 A g^?1, respectively. The results proved the suitability of the electrosynthesized nanoparticles for use in supercapacitors. Furthermore, this work provides a facile electrochemical route for the synthesis of lanthanide-doped magnetite nanoparticles.     

Analysis of multi-scale Ni particles generated by ultrasonic aided electrical discharge erosion in pure water

Electrical discharge erosion is widely applied in the fabrication process of the metallic particles in liquids. The Ultrasonic aided electrical discharge erosion is based on the spark discharge in pure water. The synthesized colloids were classified in accordance with the nano size and micron size. The higher magnifications of morphology, chemical compositions, the crystal structure of the multi-scale particles were observed and analyzed by SEM, TEM, EDS, and XRD. It is verified that ultrasonic wave influenced the morphology of micro/nanoparticles and the roughness of inner and external surfaces of hollow micro-particles. Besides, based on results of EDS, XRD, and Quantitative phase analysis, it is confirmed that nickel oxide was detected only on the surface of microparticles but the nickel oxide was easily obtained when nanoparticles were formed. In addition, ultrasound wave affected the oxidation reaction in both scales but the reaction was remarkably enhanced on nanoparticles. The DLS and LPSA were used to measure the size distributions for the nano and micron scale, respectively. The D-Values of both conditions shown that the ultrasound has an enhanced effect on decreasing the size distribution in both scales.     

Investigations on structural, optical and electrochemical properties of blue luminescence SnO2 nanoparticles

A simple solution approach has been developed to synthesis SnO₂ nanoparticles using polyethylene glycol as stabilizer. X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), UV–Vis absorption spectroscopy, photoluminescence (PL) emission spectroscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to characterize the nanoparticles. XRD, HR-TEM and AFM indicate that the SnO₂ nanoparticles correspond to tetragonal crystal structure with size ranges below Bohr’s exciton radius. UV–Vis absorption spectrum showed band gap exhibiting a 1.3 eV shift from that of bulk SnO₂ structures. The blue emission owing to transition of an electron from conduction band to deeply trapped hole in SnO₂ nanoparticles was analyzed using PL spectroscopy. The charge transfer capability had been investigated using CV and EIS in different electrolytes. A detailed exploration on confinement effect that occurred in SnO₂ nanoparticles, mechanism behind visible emission and electron transfer mechanism in different electrolyte was discussed.     

The effects of surface treatment and stannate as an electrolyte additive on the corrosion and electrochemical performances of pure aluminum in an alkaline methanol–water solution

Pure aluminum electrodes were treated in alkaline stannate solutions, and the effects of some factors such as NaOH content and treating time were explored. The corrosion and electrochemical performances of the modified aluminum anodes in 4.0 M KOH methanol–water mixed solutions containing a methanol/water volume ratio of 7:3 (30% water) with and without stannate were investigated by means of hydrogen collection, polarization curve, galvanostatic discharge, scanning electron microscopy (SEM), and energy dispersive analysis of X-ray (EDAX). Metallic tin with high hydrogen evolution overpotential was deposited in aluminum surfaces by the modification treatments using stannate, resulting in the relatively low corrosion rate and markedly enhanced discharge performance of the modified aluminum anodes. In our experimental range the aluminum electrode treated in the solution with 0.1 M NaOH for 30 min showed lower corrosion rate and better discharge performance. The addition of Na₂SnO₃ in 4.0 M KOH methanol–water mixed solutions with 30% water inhibited the corrosion of the aluminum electrodes modified in the treating solution with 0.1 M NaOH for 30 min, resulting from the deposition of tin with high hydrogen evolution overpotential in aluminum surfaces. The deposition of metallic tin on the electrode surface and the existence of stannate in the electrolytes were responsible for the notable enhancement in the discharge performance of the modified aluminum anode.     

A non-aqueous nickel–manganese sulfide on rGO wrapped Ni-foam as a supercapacitor advanced electrode material

Development of sulfide-based electrodes for non-aqueous electrolytes is a promising research area in supercapacitor applications. In this present work a novel and safe non-aqueous electrolyte can increase the specific capacitance in a wider range of potential window for electrochemical double layer capacitance (EDLCs). Herein, pristine NiS, MnS, and ternary metal composites of NiMnS/rGO-0.05 wt%, NiMnS/rGO-0.1 wt% and NiMnS/rGO-0.15 wt% are synthesized via one-step hydrothermal route. The fabricated supercapacitor electrodes performance was assessed using cyclic voltammetry, galvanostatic charge and discharge, and electrochemical impedance spectroscopy with 1 M tetraethylammonium tetrafluoroborate in acetonitrile. The as-prepared NiMnS/rGO-0.15 wt% electrode achieves an excellent specific capacitance of 352 F g^?1 at a scan rate of 5 mV s^?1 with capacitance retention of 82% through 10,000 successive cycles. Remarkably, the NiMnS/rGO-0.15 wt% composite indicates its superior electrochemical behavior as an electrode material in a non-aqueous electrolyte.

     

Self-activated ‘green’ carbon nanoparticles for symmetric solid-state supercapacitors

Tuning of porosity and surface properties of nanoparticles especially on carbon-based nanomaterials, adopting a ‘greener’ or self-activation synthesis technique for electrical charge storage, is progressing. Herein, we report the self-activation of Teak wood sawdust in a nitrogen atmosphere at different activation temperatures to synthesize carbon nanoparticles. The activated carbon nanoparticles synthesized at 900 °C exhibits a maximum?~?360 m² g^?1 surface area with?~?2 nm average pore size diameter. Five electrolytes viz. KOH, KCl, Na₂SO₄, NaCl, and H₃PO₄ are used for studying the supercapacitance nature of the activated carbon nanoparticles in a 3-electrode configuration. A maximum specific capacitance of?~?208 F g^?1 @ 0.25 A g^?1 is obtained in 1 M KOH as the electrolyte. Two symmetric supercapacitors, aqueous (1 M KOH) and solid-state (PVA/KOH), are fabricated, and their performance difference is compiled. The solid-state symmetric supercapacitor performs in a wider voltage window (1.7 V) with a superior energy density of 27.1 Wh kg^?1 at a power density of 178 W kg^?1.

Graphical abstract

     

Preparation of CuO nanopowders and their catalytic activity in photodegradation of Rhodamine-B

CuO nanopowders have been successfully synthesized in two different morphologies from same precursor using a facile gel to crystalline (reflux) and co-precipitation synthesis routes. SEM and TEM observations indicate that the morphology of the products depends on preparation technology, while XRD shows the formation of CuO nanocrystals with monoclinic crystal system in both cases. A comparison of morphological characterization of CuO nanopowders showed flower-like and aggregated nanoparticles in the form of clusters using reflux and co-precipitation techniques, respectively. Photocatalytic activity of the products in the aqueous solution of Rhodamine-B has been investigated under UV-light for a given time using UV–visible spectroscopy and the mineralization of organic substance was measured by total organic carbon (TOC) analysis. It was observed that the photocatalytic activity in the presence of flower-like CuO nanopowders was higher than that of observed with aggregated nanoparticles. Also the mechanisms for the formation of CuO nanopowders and the obtained results of photocatalytic degradation of Rhodamine-B are discussed.     

Suppression of H2S gas generation from the 75Li2S·25P2S5 glass electrolyte by additives

Solid electrolytes in the system Li₂S–P₂S₅ are attractive for all-solid-state lithium batteries since the electrolytes have high lithium ion conductivities and wide electrochemical windows. In particular, the 75Li₂S·25P₂S₅ (mol%) glass showed the highest stability to moisture in the system Li₂S–P₂S₅ because the amount of H₂S gas generated from the glass was the smallest in the system Li₂S–P₂S₅. In this study, several additives such as metal sulfides and metal oxides (FeS, CuO, etc.) were mixed with the 75Li₂S·25P₂S₅ glass in order to suppress H₂S gas generation from the sulfide glasses in air. The addition of more than 30 mol% FeS greatly decreased H₂S gas generation from the sulfide glass in air. In the case of the FeS addition, sulfur crystal was precipitated and the 75Li₂S·25P₂S₅ glass changed to Li₃PO₄ crystal after a reaction with water. On the other hand, the addition of 30 mol% CuO dramatically decreased H₂S gas generation from the sulfide glass in air. In the case of the CuO addition, Cu₃PS₄ crystal was precipitated after the reaction with water. Furthermore, the 75Li₂S·25P₂S₅ glass added with 30 mol% FeS or CuO showed relatively high conductivities of more than 10^?4 S cm^?1 at room temperature. Therefore, the 75Li₂S·25P₂S₅ glass added with FeS or CuO was expected to be a suitable solid electrolyte material for all-solid-state batteries.     

Polyaniline–CuO hybrid nanocomposites: synthesis, structural, morphological, optical and electrical transport studies

Thin films of semiconducting polyaniline (PANi) nanofibers reinforced with copper oxide (CuO) nanoparticles (NPs) were prepared on glass substrate using spin coating technique. Polyaniline (PANi) have been synthesized by chemical oxidative polymerization method with monomer aniline in presence of (NH₄)₂S₂O₈ as an oxidant at 0 °C. The copper oxide (CuO) nanoparticles were synthesized by sol–gel method. Physical properties of nanocomposite (NCs) films were characterized and analyzed by X-ray diffraction, Scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, UV–vis spectroscopy, Two probe resistivity measurement technique and Thermo-emf measurement. Structural analysis showed that the crystal structure of CuO is not disturbed in the PANi–CuO hybrid nanocomposite. Surface morphology study shows the uniform distribution of CuO nanoparticles in PANi matrix. FTIR and UV–Visible studies confirm the presence of polyaniline in emeraldine base form in the composites and suggest incorporation of CuO in polymer. Two probe electrical resistivity measurements of nanocomposites (NCs) film revealed that the resistivity of PANi increases with increasing content of CuO NPs.     

Electrochemical deposition of Ni–TiN nanocomposite coatings and the effect of sodium dodecyl sulphate surfactant on the coating properties

Ni–TiN nanocomposite coatings were prepared by using electrochemical deposition in a Watt’s bath containing TiN particles to increase the hardness of Ni. The effects of deposition current density, electrolyte agitation speed and the number of particles in the solution on the amount of incorporated particles in the coating process were investigated. The optimum deposition current density of 4 A dm^?2 and agitation speed of 450 rpm were obtained. The effect of sodium dodecyl sulphate (SDS) anionic surfactant on the amount of particles in the coatings was investigated. It was observed that the maximum amount of incorporated particles, with a value of 7.5% by volume, was created in the current density of 4 A dm^?2, stirring rate of 450 rpm, 30 g l^?1 TiN particles and in the presence of 0.6 g l^?1 SDS anionic surfactant.