Cyclic Voltammometry Research Articles

Investigations on supercapacitor performance of novel ZnO-CeO2-rGO nanohybrid prepared via hydrothermal method for energy storage applications and their charge storage mechanism

Nanohybrids which can utilize the synergistic effect to enhance the electrochemical activity as an electrode material for supercapacitor has gained immense interest recently.Here,we report a ZnO-CeO2-rGO ternary nanohybrid synthesized via hydrothermal method which can combine the pesuedocapacitance nature of transition metal oxide and electric double layer behavior of reduced graphene oxide. The electrochemical activity was thoroughly investigated using cyclic voltammometry(CV) and galvanostatic charge discharge for the ternary using a two electrode set up with 2 M KOH as the electrolyte. Cyclic stability analysis was done and impedance analysis was carried out using electrochemical impedance spectroscopy. Among the samples the best electrochemical performance was observed for ZnO –CeO2-rGO (Ter-2) with weight ratio 85:10:5. Ter-2 exhibited specific capacitance of 26 F/g from CV in the 2-electrode setup and a capacity retention as high as 93 % even after 5000 cycles of charge-discharge. It was observed that the addition of rGO improved the cyclic stablity as well as specific capacitance. Systematic analysis of charge storage mechanism was done using Dunn's and Trasatti's method. The results substantiate that Ter-2 is a potential supercapacitor electrode material with excellent electrochemical activity.

Employing a 100 °C-dried mixture that contained KMnO4 and SnCl4 as an anode material for lithium ion batteries

A novel finding, that the 100 °C-dried mixtures that contained KMnO4 and SnCl4 can be employed as anode materials for lithium ion batteries (LIBs), was reported for the first time in this work. In this work, the samples with Mn to Sn atomic ratios of 2:1, 1:1, 0.5:1 and 0:1 were respectively nominated as sample a, b, c and d. The physicochemical properties of the synthesized materials were mainly examined by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD results revealed that the main diffraction peaks assigned to KMnO4 were displayed in sample a and b, and some novel diffraction peaks were exhibited by sample c, and no typical diffraction peaks were displayed by sample d. The presence of irregular particles with no particular morphologies in all prepared samples was demonstrated by the SEM images. The electrochemical performances of the prepared samples were chiefly studied using galvanostatic charge-discharge tests, cyclic voltammometry (CV) and electrochemical impedance spectroscopy (EIS). The consequences of the electrochemical measurements indicated that sample c delivered a specific capacity of 225 mAh g−1 at 100 mA g−1 after 20 cycles, and also, at the current density of 700 mA g−1, the discharge capacity of sample c was still maintained as high as 130 mAh g−1 after 10 cycles. A novel group of anode material, i.e., the dried mixtures that contained KMnO4 and SnCl4, was developed in this work, which was very beneficial to the further development of LIBs anode materials mainly because of the rather lower preparation cost and the very simple preparation process.

Electrochemical co-reduction of Y(III) and Zn(II) and extraction of yttrium on Zn electrode in LiCl-KCl eutectic melts

This work presents an electrochemical study of Y(III) ions on W electrode and liquid Zn electrode and co-reduction mechanism of Y(III) and Zn(II) on W electrode in LiCl-KCl eutectic melts. Cyclic voltammogram and current reversal chronopotentiogram revealed that the electrochemical reaction of Y(III) on W electrode proceeds a single step mechanism of Y(III) to Y(0). On liquid Zn electrode, the deposition potential of Y(III) is more positive than that on W electrode due to the formation of Y-Zn solution and the reduction process was found to be a diffusion controlled and quasi-reversible at lower scan rate of 0.1 V/s. Based on the results of cyclic voltammometry, square wave voltammetry, and chronopoteniometry, the Y-Zn intermetallics could be formed by co-reduction process of Y(III) and Zn(II) on W electrode in LiCl-KCl-ZnCl2-YCl3 molten salts. Moreover, the electrochemical extracting metallic Y was conducted by galvanostatic and potentiostatic electrolysis on liquid Zn electrode. Electrolysis products consisted of Zn and YZn12 phases characterized by scanning electron microscopy with energy dispersive spectrometry and X-ray diffraction. Meanwhile, the change of Y(III) concentration in LiCl-KCl eutectic melts was detected by inductive coupled plasma atomic emission spectrometer and the extraction efficiency could be estimated.

Cyclic Voltammometry of Binderless Activated Carbon Monoliths based supercapacitor from Mixtures of Pre-carbonized of Fibers of Empty Fruit Bunches and Green Petroleum Coke

<p>Binderless activated carbon monoliths (BACMs) prepared from mixtured of pre-carbonized of fibers of oil palm empty fruit bunches (EFB) and green petroleum coke were used for preparing the carbon based supercapacitor cells. The symmetrical supercapacitor cells were fabricated by using two BACMs electrode prepared for each selected holding time of activation and various compression pressure. The electrochemical behavior of supercapacitor cells were measured at room temperature by using cyclic voltammetry (CV) technique. The maximum specific capacitance (C<sub>sp</sub>) of the cells values were 35.9 and 82.5 F/g for holding time of activation of 1.5 and 2 h, respectively, at the compression pressure of 7.5 metric tons. </p>

Cyclic Voltammometry of Binderless Activated Carbon Monoliths based supercapacitor from Mixtures of Pre-carbonized of Fibers of Empty Fruit Bunches and Green Petroleum Coke

<p>Binderless activated carbon monoliths (BACMs) prepared from mixtured of pre-carbonized of fibers of oil palm empty fruit bunches (EFB) and green petroleum coke were used for preparing the carbon based supercapacitor cells. The symmetrical supercapacitor cells were fabricated by using two BACMs electrode prepared for each selected holding time of activation and various compression pressure. The electrochemical behavior of supercapacitor cells were measured at room temperature by using cyclic voltammetry (CV) technique. The maximum specific capacitance (C<sub>sp</sub>) of the cells values were 35.9 and 82.5 F/g for holding time of activation of 1.5 and 2 h, respectively, at the compression pressure of 7.5 metric tons. </p>

(Invited) Electrochemical Bistability of Porphyrin in Supramolecular Porphyrin/Phthalocyanine Assembly

Recently, we have reported the formation of a porphyrin/phthalocyanine heterodimer in which cofacially stacked porphyrin and phthalocyanine are linked together by fourfold rotaxane (Figure 1). Mechanically interlocked supramoelcular linkages such as catenanes and rotaxanes are flexible enough to provide switching properties of the interactions among the components in the assemblies. We have reported supramolecular arrays of porphyrin and phthalocyanine and intramolecular electronic communication between the components. In this paper, we would like to reveal the electrochemical bistability of the porphyrin in the supramolecular assembly of a poprhyrin and a phthalocyanine connected by fourfold rotaxane linkage. Redox bistable systems are capable for taking two stable redox states separated by the energy barrier at the given electrochemical potential depending on the direction of the potential scan. During the negative scan on the cyclic voltammometry of 3, the porphyrin (Por) moiety was reduced into the anion radical (Por•–) at –1.72 V (vs. Fc/Fc+). Por•– generated was immediately protonated by intra- or inter-molecular proton transfer from the phosporamidate stopper of 3 to afford a neutral radical (PorH•). In the opposite (positive) scan, PorH• was not reoxidized into neutral Por until the potential reached at –0.94 V. Therefore, the two redox states, Por and PorH•, can exist stably at the same potential region depending on the direction of the potential scan. Figure 1

Improving cyclic stability of lithium nickel manganese oxide cathode for high voltage lithium ion battery by modifying electrode/electrolyte interface with electrolyte additive

We report a new approach to improve the cyclic stability of lithium nickel manganese oxide (LiNi0.5Mn1.5O4) cathode, in which the cathode/electrolyte interface is modified by using prop-1-ene-1, 3-sultone (PES) as an electrolyte additive. The interfacial properties of LiNi0.5Mn1.5O4 cathode in PES-containing electrolyte have been investigated by scanning electron spectroscopy (SEM), transmission electron microscopy (TEM), thermal gravimetry (TG), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cyclic voltammometry (CV), chronoamperometry (CA), and constant current charge/discharge test. It is found that the application of PES improves significantly the cyclic stability of LiNi0.5Mn1.5O4. After 400 cycles at 1C rate (1C=147mAg−1), the capacity retention of LiNi0.5Mn1.5O4 is 90% for the cell using 1.0 wt% PES, while only 49% for the cell without the additive. The characterizations from SEM, TEM, TG, XRD, and XPS confirm that the LiNi0.5Mn1.5O4/electrolyte interface is modified and a protective solid electrolyte interface film is formed on LiNi0.5Mn1.5O4 particles, which prevents LiNi0.5Mn1.5O4 from destruction and suppresses the electrolyte decomposition.

Improvement of electrochemical and structural properties of LiMn2O4 spinel based electrode materials for Li-ion batteries

Spinel LiMn2O4 and LiM0.02Mn1.98O4 (where M is Zn, Co, Ni and In) were produced via facile sol–gel method and Cu/LiMn2O4, Cu/LiM0.02Mn1.98O4, Ag/LiMn2O4 and Ag/LiM0.02Mn1.98O4 binary composite electrode materials were produced via electroless coating techniques as a positive electrode material for Li-ion batteries. The phase composition, morphology and electrochemical properties of the synthesized materials were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), cyclic voltammometry (CV), galvanostatic charge–discharge tests and electrochemical impedance spectroscopy (EIS). The synthesized cathode active materials are characterized as single phase spinel LiMn2O4 with degree of crystallization and uniform particle size distribution. Best results were obtained with electrodes substituted with In and an initial discharge capacity of 134 mAhg−1 after 50 cycles. The improvement in the cycling performance may be attributed to stabilization of spinel structure by smaller lattice constant when manganese ion was partially substituted with In3+ ions. EIS analysis also confirms that the obvious improvement in Ag coating is mainly attributed to the accelerated phase transformation from layered phase to spinel phase and highly stable electrolyte/electrode interface due to the suppression of electrolyte decomposition.

Electrochemically Controlled Hydrogen Bondings: Monitoring Phenylendiamines as Donors with Multiple Binding Sites by Cyclic Voltammometry and Digital Simulation

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Nb2O5 Photoelectrodes for Dye-Sensitized Solar Cells: Choice of the Polymorph

Nanowires of Nb2O5 were developed in three polymorphic forms, namely, pseudo-hexagonal, orthorhombic, and monoclinic, by electrospinning a polymeric solution and by subsequent annealing. The materials were characterized by X-ray and electron diffraction, scanning and transmission electron microscopy, BET surface area measurements, absorption spectrometry, and cyclic voltammometry. These characterizations indicate that the monoclinic phase has a higher conduction band edge compared with the other two and is likely to display higher open circuit voltage in solar cells. Dye-sensitized solar cells were fabricated using the above polymorphs, and the device performances were studied. The pseudo-hexagonal phase showed higher device performance owing to its higher specific surface area compared with the others. However, when normalized, the device performances with respect to the dye-loading, the monoclinic phase gave superior performance. Studies on the charge transport properties using electrochemical impedance spectroscopy and open circuit voltage decay indicate that the monoclinic phase has high resistance against charge recombination and improved electron lifetime compared with the other phases and conventional TiO2 nanostructures. The monoclinic Nb2O5 is likely to be a material of choice as photoelectrode in dye-sensitized solar cells if its mesoporous particles with large surface area could be synthesized.

New morpholine- and piperazine-functionalized triphenylantimony(V) catecholates: The spectroscopic and electrochemical studies

Novel functionalized triphenylantimony(V) catecholates – Ph 3Sb[4-O(CH 2CH 2) 2N-3,6-DBCat] ( 1), Ph 3Sb[4-PhN(CH 2CH 2) 2N-3,6-DBCat] ( 2), Ph 3Sb[4-Ph 2CHN(CH 2CH 2) 2N-3,6-DBCat] ( 3), Ph 3Sb[4,5-Piperaz-3,6-DBCat] ( 4) and binuclear bis-catecholate Ph 3Sb[3,6-DBCat-4-N(CH 2CH 2) 2N-4-3,6-DBCat]SbPh 3 ( 5) were synthesized by the oxidative addition reaction of corresponding o-quinones with triphenylantimony. The [4-O(CH 2CH 2) 2N-3,6-DBCat] 2−, [4-PhN(CH 2CH 2) 2N-3,6-DBCat] 2−, [4-Ph 2CHN(CH 2CH 2) 2N-3,6-DBCat] 2− and [4,5-Piperaz-3,6-DBCat] 2− are 4-(morpholin-1-yl)-, 4-(4-phenyl-piperazin-1-yl)-, 4-(4-dephenylmethyl-piperazin-1-yl)-, and 4,5-(piperazin-1,4-diyl)-3,6-di- tert-butyl-catecholate dianionic ligands, correspondingly. Complexes 1–5 were characterized in details by IR-, 1H and 13C NMR spectroscopy and cyclic voltammometry. Molecular structure of 4·CH 3OH was determined by X-ray crystallography to be a distorted tetragonal–pyramidal. The NMR spectroscopic and electrochemical investigations of complexes in the presence of air reveal the reactions of complexes with dioxygen leading to the formation of spiroendoperoxides of 1,2,4,3-trioxastibolane type in a NMR yield of 25–37%.

Cobalt(III) complexes of some aromatic thiohydrazides – Synthesis, characterization and structure

[Co(NH 3) 5Cl]Cl 2 forms neutral 1:3 complex by reaction with aromatic thiohydrazides, i.e. thiobenzhydrazide, o-hydroxythiobenzhydrazide, thiophen-2-thiohydrazide and furan-2-thiohydrazide. All these complexes are diamagnetic and have been characterized by elemental analysis and combination of spectroscopic methods. Cyclic voltammometry of the complexes shows irreversible metal centered and ligand centered electron transfer reactions. One complex, tris- o-hydroxythiobenzhydrazidocobalt(III), has been crystallized from DMSO solution to produce solvated crystals and its structure has been established by X-ray crystallography. Cobalt(III) ion is linked through three hydrazinic nitrogen and three sulfur atoms of three identical deprotonated ligand molecules in a distorted octahedral environment. Involvement of –OH group in intramolecular and intermolecular hydrogen bonding is crucial for crystal formation.

Electrochemical Performances of Electroactive Nano-LayeredOrganic-Inorganic Perovskite Containing Trivalent Iron Ion and its Use for a DNA Biosensor Preparation

A steady nano organic-inorganic perovskite hybrid with [H23-AMP]3/2Fe(CN)6 (3-AMP = 3-methylaminopyridine) was prepared in the air. The structure is an unusual layered organic-inorganic type. The resulting hybrid enveloped in paraffin to prepare [H23-AMP]3/2Fe(CN)6 paste electrode (HPE) shows good electrochemical activity and a couple of oxidation and reduction peaks with potential of cyclic voltammometry (CV) at around 440 mV and 30 mV. Compared with that on CPE, oxidation potential of Fe(CN)6 3− on HPE shifts negatively 259.7 mV and that of reduction shifts positively 338.7 mV, which exhibits that [H23-AMP]3/2Fe(CN)6 can accelerate the electron-transfer to improve the electrochemical reaction reversibility. Such characteristics of [H23-AMP]3/2Fe(CN)6 have been employed to prepare the DNA biosensor. The single-strand DNA (ssDNA) and double-strand DNA (dsDNA) immobilized on HPE, respectively, can improve the square wave voltammometry (SWV) current and SWV potential shifts positively. The effect of pH was evaluated. And there is hybridization peak on SWV curve using HPE immobilized ssDNA in the complementary ssDNA solution. And HPE immobilized ssDNA can be utilized to monitor the DNA hybridization and detect complementary ssDNA, covering range from 3.24 × 10−7 to 6.72 × 10−5 g/mL with detection limit of 1.57 × 10−7 g/mL. The DNA biosensor exhibits a good stability and reproducibility.

Antimony(V) catecholato complexes based on 4,5-dialkylsubstituted o-benzoquinone. The spectroscopic and electrochemical studies. Crystal structure of [Ph 4Sb] +[Ph 2Sb(4,5-Cat) 2] −

Triphenylantimony(III) and triethylantimony(III) readily react with 4,5-(1,1,4,4-tetramethyl-butane-1,4-diyl)- o-benzoquinone to form catecholato complexes R 3Sb(4,5-Cat) (R = Ph ( 1), Et ( 2); 4,5-Cat is dianionic 4,5-(1,1,4,4-tetramethyl-butane-1,4-diyl)-catecholate). In polar solvents (CHCl 3, acetone) complex 1 transforms easily to ionic complex compound [Ph 4Sb] +[Ph 2Sb(4,5-Cat) 2] − ( 3) with diphenyl-bis-[4,5-(1,1,4,4-tetramethyl-butane-1,4-diyl)-catecholato]antimony(V) complex anion. Complexes were characterized by IR, 1H, 13C NMR spectroscopy, cyclic voltammometry. Molecular structure of 3·CHCl 3 was confirmed by X-ray analysis. Cyclic voltammometry of 1 and 3 shows that both complexes undergo reversible one-electron oxidation to quite stable paramagnetic o-semiquinonato species [Ph 3Sb(4,5-SQ)] + and [Ph 2Sb(4,5-SQ)(4,5-Cat)] (0.75 and 0.49 V in CH 2Cl 2 vs. Ag/AgCl/KCl, respectively).

The effect of vapor-grown carbon fiber as an additive to the catalyst layer on the performance of a direct methanol fuel cell

Vapor-grown carbon fibers (VGCFs) were added to the anode catalyst layer of a direct methanol fuel cell to improve the cell performance through structural modification of the catalyst layer. The amount of VGCF varied up to 6 wt.% with respect to the weight of the PtRu black catalyst that was used. A catalyst layer with 2 wt.% VGCF loading showed the best cell performance. The electrodes that included the catalyst, VGCF, and gas diffusion layer, were directly examined by electron microscopic analyses. Electrochemical methods, such as cyclic voltammometry and impedence analysis, were applied to investigate the actual role of VGCF in the electrode. The porosity of the catalyst layer was increased by the addition of the fibers. This was clearly observed in pore diameters less than 1 μm. Sub-micron pore diameters are significant as they relate to micro-diffusive transport, compared to the macro-diffusion experienced by the large pores in the GDL. However, improved mass transport was only observed for 2 wt.% VGCF loading, probably due to insufficient optimization of the cell design. Microstructural and electrochemical analyses indicated that the improved performance was mainly ascribed to an increased electrochemically active surface area of the catalyst.

Effects of the Substituents in the TpxCu Activation of Dioxygen: An Experimental Study

A series of TpxCu(I) complexes (Tpx=homoscorpionate ligand) have been reacted in solution with dioxygen at room temperature. Two different behaviors have been observed: the already described reaction with O2 or the lack of any transformation. The trend has been correlated with the electronic density at the metal center, and that has been evaluated by means of cyclic voltammometry studies as well as by IR studies with the TpxCu(CO) complexes. The data collected indicate that the former could serve as a better tool to predict such transformation, establishing a limit above which the complexes are stable under oxygen in solution. Catalytic tests carried out under oxygen have demonstrated that the use of an inert atmosphere is not a requirement in some cases.

Al Electrode Modified by Au Atoms as a Novel Electrode for Electrocatalytic Oxidation of Thiosulfate

AbstractAn aluminum electrode modified with gold atoms was introduced as a novel electrode. Gold atoms were deposited both chemically and electrochemically onto the aluminum electrode to make an aluminum/gold (Al/Au) modified electrode (ME). The experimental results showed that the Al/Au modified electrode prepared by chemical deposition, exhibits much more current than the electrochemical deposition method. The electrochemical behavior of the Al/Au modified electrode was studied by cyclic voltammometry. This modified electrode showed two pairs of peaks, a1c1 and a2c2, with surface‐confined characteristics in a 0.5 M phosphate buffer. The dependence of Epa of the second peak (a2c2) on pH shows a Nernestian behavior with a slope of 55 mV per unit pH. The effect of different supporting electrolytes, solution's pH and different scan rates on electrochemical behavior of Al/Au modified electrode was studied. Au deposited electrochemically on a Pt electrode (Pt/Au) was also used as another modified electrode. A comparative study of electrochemical behavior of bare Al, Pt/Au and Al/Au modified electrodes showed that both Pt/Au and Al/Au electrodes have the ability of electrocatalytic oxidation of S2O32−, but the electrocatalytic oxidation on the latter was better than the former. The kinetics of the catalytic reaction was investigated by using cyclic voltammetry and chronoamperometry techniques. The average value of the rate constant for the catalytic reaction and the diffusion coefficient were evaluated by means of chronoamperometry technique.

Preparation and characterization of conducting poly(vinyl chloride)-g-poly(aniline) copolymer

The electrically conductive graft (g) copolymer, Poly(vinyl chloride)-g-poly(aniline) (PVC-g-PAni) was prepared by the electrochemical polymerization of aniline using a precursor polymer, poly(vinyl-1,4-phenylenediamine) (PVPD) which was spin-coated on a working electrode. PVPD was synthesized chemically by reacting PVC with potassium 1,4-phenylenediamine salt and characterized using FT-IR and 1 H NMR spectroscopy. The electrochemical, electrical, morphological and thermal properties of PVC-g-PAni copolymer were investigated and compared with those of a PVC/PAni composite. The results of cyclic voltammometry, chronoamperometry, scanning electron microscopy, and conductivity measurement support the formation of a graft copolymer. The conductivity of the graft copolymer was about 0.17 S/cm which was about one order of magnitude higher than that of the composite.

Effects of Ag-photodeposition on photocurrent of an ITO electrode modified by a hybrid film of TiO 2 nanosheets

We performed the photodeposition of Ag clusters onto a TiO 2 nanosheet hybridized with an amphiphlic Ru(II) complex (denoted by TiO 2–Ru/Ag). Firstly a floating monolayer of [Ru(phen) 2(dC18bpy)](ClO 4) 2 (phen = 1,10-phenanthroline, dC18bpy = 4,4 ′-dioctadecyl-2,2 ′-bipyridyl) was formed on an aqueous dispersion of exfoliated layered titanate, (TBAOH) x Ti 2− x/4 □ x/4 O 4 · H 2O ( x∼0.7;□, vacancy; TBAOH = tetrabutylammonium hydroxide) (denoted as TiO 2 nanosheet). The monolayer acted as the organic part for the hybridization of TiO 2 particles in an aqueous phase. A hybrid film of TiO 2 nanosheet and an amphiphilic metal complex (denoted by TiO 2–Ru) was transferred onto an indium tin oxide substrate by the vertical dipping method. Thereafter the electrode was immersed in 1.0 M AgNO 3 for 10 min and rinsed with water. The electrode was irradiated for 30 min by a Xe-lamp (150 W). Atomic force microscope, X-ray photoelectron spectra and cyclic voltammometry showed the formation of silver nanoparticles with a radius of 20–150 nm. The photocurrent response was measured in the potential range of 0.2–1.2 V (vs. Ag|AgCl|KCl(sat)) under the illumination of light (>350 nm). The current increased 1.7 times when the layer number of hybrid films increased from one to two. It should be emphasized that such an increase of photocurrent with a layer number was not observed in the absence of Ag particles.

Synthesis and Properties of First Well-Defined Phosphole-Containing π-Conjugated Polymers

Novel π-conjugated polymers 10a−c having the phosphole unit were prepared by palladium complex-catalyzed coupling of bis(p-bromophenyl)phosphole (7) with diethynylarenes 9a−c. The obtained polymers 10a−c were regio-regulated with the 2,5-substituted phosphole unit and characterized by 1H and 31P NMR. Polymers 10a−c were found to be an extended π-conjugated system according to the results of the UV−vis absorption spectra. In the fluorescence emission spectra of 10, moderate emission peaks were observed in the visible region. These polymers showed electron-donating properties in cyclic voltammometry measurements.