Symmetric supercapacitors are fabricated by carbon nanofibers (CNF) and activated carbon (AC) using similar proportions of 7 wt% polyvinylidene fluoride (PVDF) polymer binder in an aqueous ...electrolyte. In this study, a comparison of porous texture and electrochemical performances between CNFs and AC based supercapacitors was carried out. Electrodes were assembled in the cell without a current collector. The prepared electrodes of CNFs and AC present Brunauer-Emmett-Teller (BET) surface area of 83 and 1042 m
2
/g, respectively. The dominant pore structure for CNFs is mesoporous while for AC is micropore. The results showed that AC provided higher specific capacitance retention up to very fast scan rate of 500 mV/s. AC carbon had a specific capacitance of 334 F/g, and CNFs had 52 F/g at scan rate 5 mV/s in aqueous solution. Also, the results indicate the superior conductivity of CNFs in contrast to AC counterparts. The measured equivalent series resistance (ESR) showed a very small value for CNFs (0.28 Ω) in comparison to AC that has an ESR resistance of (3.72 Ω). Moreover, CNF delivered higher specific power (1860 W/kg) than that for AC (450 W/kg). On the other hand, AC gave higher specific energy (18.1 Wh/kg) than that for CNFs (2 Wh/kg).This indicates that the AC is good for energy applications. Whereas, CNF is good for power application. Indeed, the higher surface area will lead to higher specific capacitance and hence higher energy density for AC. For CNF, lower ESR is responsible for having higher power density.
Both CNF and AC supercapacitor exhibit an excellent charge-discharge stability up to 2500 cycles.
CdS thin films have been deposited onto FTO/glass substrates by two different techniques, electrochemical deposition (ECD) and chemical bath deposition (CBD). Feasibility of using these two film ...types in photoelectrochemical processes has been critically investigated here. The films were comparatively characterized by a number of techniques (solid state absorption spectra, solid state photoluminescence spectra, XRD and SEM). PEC characteristics of the electrodes, including current density–voltage (J–V) plots, conversion efficiency (η), stability and fill-factor (FF) were then studied. The results show that both systems involved nano-sized CdS particles living in coagulates. The ECD was thinner and more uniform than the CBD system. The CBD films were more effective in PEC processes than the ECD counterparts. Effect of annealing on characteristics of both electrode systems has been investigated. Annealing enhanced both film characteristics, but the CBD was affected to a higher extent, and the annealed CBD film was more effective than the ECD counterpart.
Display omitted Annealed CBD-prepared CdS films showed larger particle coagulates and higher stability under PEC conditions than the ECD counterparts.
► ECD technique yields thinner but more uniform CdS films than CBD. ► CdS films prepared by ECD were used in PEC processes for first time. ► CBD films of CdS are more effective in PEC processes than ECD counterparts.
Natural molecular dye, anthocyanin, is described here as safe sensitizer for TiO2 particles in photo-degradation of organic contaminants in water. The dye is a promising replacement for the more ...costly and hazardous heavy metal based systems, such as CdS particles and Ru-compounds. TiO2/anthocyanin effectively catalyzed the photo-degradation of methyl orange contaminant under solar simulator radiation. The new TiO2/anthocyanin catalyst showed comparable efficiency to earlier systems, while avoiding their hazardous nature. When supported onto activated carbon (AC) particles, the resulting AC/TiO2/anthocyanin system showed enhanced efficiency and ease of recovery from the catalytic reaction mixture. The natural dye molecules showed the tendency to degrade under photo-degradation conditions, just like earlier hazardous sensitizers. However, complete mineralization of anthocyanin occurred leaving no traces of organic species in solution. Sensitizer degradation caused deactivation of the supported catalyst on recovery. Such a shortcoming was overcome by re-treatment of the recovered catalysts with fresh dye. Effects of different reaction parameters on the catalyst efficiency were studied. A mechanism, similar to earlier CdS-sensitized catalyst systems, is proposed for the TiO2/anthocyanin catalyst.
Porous biphasic bioceramics that contain hydroxyapatite and tricalcium phosphate were synthesized in this study using luffa cylindrical fibres (LCF) as the template. In addition to improving the pore ...structure, using this template led to a chemical coating of the pores´ internal surfaces by important minerals such as magnesium and phosphorous from the LCF residue. Evaluation of our preliminary results suggests promising applications in bone tissue engineering. The synthesized porous bioceramics were characterized in view of their microstructural, physical, and in vitro features. They showed a trimodal pore system comprising a nano-pore network, smaller macropore with diameters of 5 to 100 m, and cylindrical macropores with diameters from 100 to 400 m; and 75% of interconnected porosity was confirmed by Mercury intrusion porosimetry and SEM images. Enhanced cell adhesion of the internal pore surfaces generated long and extended cells inside the macropores. SEM images show how the cells adhered to bioceramic surfaces and developed cytoplasmic extensions. Their proliferation in vitro demonstrates that the scaffold architecture and mineral composition are suitable for mesenchymal stem cell seeding and growth.
In this work, the electrochromic and structural properties of NiO thin films prepared using optimized low value electrodeposition parameters were studied. The optimized parameters were deposition ...current density, molar concentration of nickel nitrate solution, and deposited charge density. The highest electrochromic characteristics corresponded to deposition parameters of −0.05 mA/cm2 deposition current density, 0.02 M of Ni(NO3)2.6H2O solution, and charge density of 80 mC/cm2. For this optimized film, at 630 nm wavelength, the transmittance modulation ΔT was 76%, the efficiency η was 19 cm2/C, the charge reversibility Qc/Qa was 97%, and a remarkable contrast ratio CR of 5.9. In addition, a good cycling stability was confirmed up to 900 cycles. Optimized NiO thin films were poorly crystallized exhibiting a nano-flake structure, high porosity, and homogeneity.
•Low value electrodeposition parameters were used to prepare optimized NiO electrochromic film.•Optimized deposition parameters are Jd = -0.05 mA/cm2 , 0.02 M of Ni(NO3)2.6H2O solution, and charge density of 80 mC/cm2•Optimized film has ΔT of 76 %, efficiency η was 19 cm2/C, Qc/Qa was 97%, CR of 5.88, and cycling stability up to 900 cycles.•Optimized NiO thin films were poorly crystallized exhibiting a nano-flake structure, high porosity, and homogeneity.
Two new neutral mixed-ligand cobalt(II) complexes, CoCl2(dmdphphen) 1 and Co(NCS)2(dmdphphen) 2, where dmdphphen is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, were synthesized and characterized ...by an elemental analysis, UV-Vis, IR, TG/DTA, cyclic voltammetry CV, and single X-ray diffraction. Complex 2 crystallized as monoclinic with a space group P21/c. Co(II) ions are located in a distorted tetrahedral environment. TG/DTA result shows that these complexes are very stable and decomposed through one-step reaction. The two complexes exhibit a quasireversible one-electron response at −550 and 580 mV versus Cp2Fe/Cp2Fe+, which has been assigned to Co(I)/Co(II) and Co(II)/Co(III) couples. Absorption spectral studies reveal that such complexes exhibit hypochromicity during their interaction with CT-DNA.
Mineralization of phenazopyridine, 1, in water, under solar-simulator radiation was efficiently achieved using nanoparticle CdS-sensitized rutile TiO(2), TiO(2)/CdS, 2, as photo-catalysts. Despite ...that, 2 showed two main drawbacks. Firstly, the system was difficult to recover by simple filtration, and demanded centrifugation. Secondly, the sensitizer CdS showed relatively high tendency to leach out hazardous Cd(2+) ions under photo-degradation reaction conditions. In an attempt to solve out such difficulties, 2 was supported onto sand surface. The sand/TiO(2)/CdS system, 3, was easier to recover but showed slightly lower catalytic activity compared to 2. On the other hand, the support failed to prevent leaching of Cd(2+). This indicates limited future applicability of CdS-sensitized TiO(2) photo-catalyst systems, in solar-based water purification strategies, unless leaching out tendency is completely prevented.
Natural molecular dye, anthocyanin, is described here as safe sensitizer for TiO
2 particles in photo-degradation of organic contaminants in water. The dye is a promising replacement for the more ...costly and hazardous heavy metal based systems, such as CdS particles and Ru-compounds. TiO
2/anthocyanin effectively catalyzed the photo-degradation of methyl orange contaminant under solar simulator radiation. The new TiO
2/anthocyanin catalyst showed comparable efficiency to earlier systems, while avoiding their hazardous nature. When supported onto activated carbon (AC) particles, the resulting AC/TiO
2/anthocyanin system showed enhanced efficiency and ease of recovery from the catalytic reaction mixture. The natural dye molecules showed the tendency to degrade under photo-degradation conditions, just like earlier hazardous sensitizers. However, complete mineralization of anthocyanin occurred leaving no traces of organic species in solution. Sensitizer degradation caused deactivation of the supported catalyst on recovery. Such a shortcoming was overcome by re-treatment of the recovered catalysts with fresh dye.
Effects of different reaction parameters on the catalyst efficiency were studied. A mechanism, similar to earlier CdS-sensitized catalyst systems, is proposed for the TiO
2/anthocyanin catalyst.
Display omitted
Activated carbons (ACs) have been used as electrode material in commercial electric double-layer capacitors (EDLC) due to their low cost, high specific surface area, and chemical stability. ...Unfortunately, the supercapacitive performance of AC is not satisfactory due to their low conductivity.On the other hand, carbon nanofibers (CNFs) based EDLC exhibit low equivalent series resistance (ESR) but not such energy storage values as AC ones. Here in this paper, we report on the synthesis of new nanocomposites based on a mixture of ACs and CNFs using a simple powder processing route and evaluating their electrochemical behavior as electrode materials in symmetric EDLC. The EDLC, with 10 wt. % CNFs in AC/CNFs as the electrodes have displayed a high conductivity and surface area resulting in the enhancement of the energy and power delivers in aqueous electrolyte.
On the contrary, with 90 wt.% CNFs in AC/CNFs as the electrodes, higher specific power, low ESR, and low value of relaxation time constant are achieved. The highest value of specific capacitance estimated is around 207 F g−1 at 5 mV s−1 and the highest specific energy is 13.2 Wh kg−1 at 1 A g−1 for the 10 wt.% CNFs in AC/CNFs.
Display omitted
PDF
