ISSN (print): 1023-1935, ISSN (online): 1608-3342 Editor-in-Chief: Aslan Yu. Tsivadze Publisher: Pleiades Publishing Indexed in: RUS White List (level 3), Scopus, Web of Science (SCIE)
Square Wave Anodic Stripping Voltammetric Determination of Paracetamol at Poly Luminol/Functionalized Multi-Walled Carbon Nanotubes Modified Glassy Carbon Electrode
In the present study an electrochemical sensor, based on glassy carbon electrode (GCE) modified by polyluminol (PLum)/functionalized multi-walled carbon nanotube (f-MWCNTs) was introduced for the determination of paracetamol. Modified electrode was made by casting the f-MWCNTs on GCE and electropolymerization of luminol on its surface. The surface morphology was investigated by scanning electron microscopy (SEM) and impedance electrochemical spectroscopy (EIS). The effective parameters on the response of the modified electrode were optimized, and the square wave anodic stripping voltammetry (SWASV) was applied for drug determination. Under the optimized conditions, at least two linear dynamic ranges (0.04–32.2 and 32.2–172.2 µM) were observed between the anodic peak currents and concentrations of PCM when PLum/f-MWCNTs/GCE was used, and its detection limit was 25 nM. The proposed electrode was successfully applied to determine PCM in pharmaceutical formulations, urine and serum samples.
A Carbon Paste Electrode Modified by Graphene Oxide/Fe3O4@SiO2/Ionic Liquid Nanocomposite for Voltammetric Determination of Acetaminophen in the Presence of Tyrosine
Herein, we introduce a novel modification process for carbon paste electrode by magnetic core–shell nanocomposite of graphene oxide/Fe3O4@SiO2 and n-hexyl-3-methylimidazolium hexafluoro phosphate as ionic liquid. Electrochemical features of this modified carbon paste electrode and its performance evaluation in simultaneous detection of acetaminophen and tyrosine via voltammetric oxidation was investigated. Moreover, diagnostic techniques including cyclic voltammetry, square wave voltammetry and chronoamperometry were applied in order to study the electrochemical oxidation behavior of this sensor toward acetaminophen. According to square wave voltammetry results, linear dynamic range between 1.0 × 10–6–1.0 × 10–3 M was observed for acetaminophen. The function of modified electrode in real samples containing acetaminophen and tyrosine was satisfactory.
The Effect of Solution pH on the Oxidation of Sulfite Ions and the Formation of Oxides on the Gold Electrode
The results of studying the effect of solution pH on the electrode process that occurs on the gold electrode in solutions of sodium sulfite, sulfuric acid, and alkali, and also in the universal buffer of Britton–Robinson (pH 2–14) are shown. In sodium sulfite solutions, this electrode process represents a combination of the oxidation of sulfite species and the formation of oxides on the gold surface that proceeds simultaneously in the same potential region. It is shown that the solution pH and the oxidation of sulfite species have no effect on the amount of gold α-oxide formed. At the same time, the solution pH has a strong effect on the oxidation of sulfite species. Thus, the voltammograms measured in solutions with pH approximately between 2 and 11 are identical, i.e., the process rate is independent of the solution acidity and its partial composition. These results suggest that in this pH region, the oxidation of sulfite ions can be interpreted by the overall reaction \(2{\text{SO}}_{3}^{{2 - }} \to {{{\text{S}}}_{{\text{2}}}}{\text{O}}_{6}^{{2 - }} + 2{\text{e}}\) to produce dithionate ions. In strongly alkaline solutions (pH 12.5–14), the oxidation potential shifts in the negative direction and the current decreases with increasing pH. These results suggest that in strongly alkaline solutions, the oxidation of sulfite ions can proceed on the partly blocked electrode surface by the reaction \({\text{SO}}_{3}^{{2 - }} + 2{\text{O}}{{{\text{H}}}^{ - }} \to {\text{SO}}_{4}^{{2 - }} + {{{\text{H}}}_{{\text{2}}}}{\text{O}} + 2{\text{e}}\) to form sulfate ions. The changeover of the mechanism of oxidation of sulfite ions takes place in a narrow potential region in solutions with pH from 11 to 12.5 and is accompanied by anomalously sharp changes in the measured current. The latter anomalies are associated with the peculiar dynamics of the process of passivation/depassivation of the electrode surface by gold oxides.
Preparation of Hydrophobic Porous Silicon by Metal-Assisted Etching with Pd-Catalyst
The process of the porous silicon layer formation by metal-assisted etching of single-crystal Si with the resistivity of ρ = 0.01 Ω cm, coated with thin Pd-film up to 100 nm thick, in HF/H2O2/H2O solution is studied. The porous silicon is studied by scanning electron microscopy and gravimetric analysis. The dependence of the silicon dissolution rate on the HF concentration, in the presence and in the absence of the Pd-film, is investigated. The anodic current facilitating the Si dissolution in the HF solutions of different concentration is studied. By using sessile drop method, the porous silicon formed by the Pd-assisted anodic etching was shown to be superhydrophobic. The porous Si wetting angle reached 172°. The free surface energy for the porous layers and the water surface tension at the porous Si are calculated. The modified Si-surfaces may found their possible use in robotics.
Electrochemical Synthesis of Multilayer Graphene Oxide by Anodic Oxidation of Disperse Graphite
The electrochemical method for synthesizing multilayer graphene oxide by the anodic oxidation of disperse graphite in sulfuric acid is proposed. The possibility of sequential dispersion of graphite in the course of its electrochemical oxidation, hydrolysis, and thermolysis is demonstrated. It is shown that the resulting nanostructured materials tend to form agglomerates in aqueous dispersions. When treated with supersonic, the size of oxidized graphite particles decreases noticeably and they form multilayer graphene oxide. Thermolysis (250°С) leads to a considerable expansion of oxidized graphite particles (the inflation coefficient 1490 cm3 g–1) and reduction of oxygen-containing functional groups. The structure of thus obtained material includes polygraphene sheets with the thickness of 0.01–0.1 µm and contains pores of 1–10 µm.
Effect of Surface Modification of Heterogeneous Anion-Exchange Membranes on the Intensity of Electroconvection at Their Surfaces
Electroconvection is the principal mechanism that allows markedly increasing the rate of ion transfer through ion-exchange membranes in intensive current regimes. In this work, we investigated the possibility of intensifying electroconvection in solution near heterogeneous MA-41 anion-exchange membrane (Shchekinoazot production) by the modifying of its surface. The use of weakly crosslinked ion-exchange resin (MA-41P) in the course of the membrane manufacturing, with subsequent chemical modification of its surface (MA-41PM), is shown to make it possible to increase the limiting current density almost twice. The value of the reduced potential drop (after subtracting the ohmic contribution), at which significant generation of H+ and OH– ions begins, is shifted from 0.8 V in the case of MA-41 to 1.7 V in the case of MA-41PM. The current density related to the onset of water splitting is equal to 0.9\(i_{{{\text{lim}}}}^{{{\text{Lev}}}},\) in the case of MA-41; 2\(i_{{{\text{lim}}}}^{{{\text{Lev}}}},\) in the case of MA-41PM (where \(i_{{{\text{lim}}}}^{{{\text{Lev}}}}\) is the theoretical value of the limiting current density). The special feature of the modified membrane behavior is the presence of a range of potential drop (between 50 and 80 mV in the reduced scale), in which the system with the MA-41PM has negative differential resistance: in this range, the potential drop decreases when the current density increases. This behavior occurs when measuring quasi-stationary I–V curves; correspondingly, in the chronopotentiogram there is a time interval, where the potential drop decreases with time. The electroconvection is intensified near a modified membrane due to a higher fraction of conductive areas on the surface of the modified membrane and the redistribution of these areas via formation of their agglomerates in the centers of the cells formed by the reinforcing mesh. Mathematical modeling shows the concentration polarization of the modified membrane being less than that of the pristine one. Meanwhile, the structure of electroconvective vortices is optimized: the vortices near the modified membrane are larger; they do not extinguish each other, unlike the case of MA-41.
Application of Black Phosphorus Nanosheets Modified Electrode for Electrochemical Determination of Ascorbic Acid
Black phosphorus nanosheets (BPNS) were synthesized through liquid exfoliation method coupling with ultrasonication. The synthesized BPNS were characterized by transmission electron microscopy, size-distribution analysis, and Raman spectroscopy. The results revealed that few layers BP nanosheets with an average lateral size of 240 nm were obtained. BPNS modified glassy carbon electrode (BPNS/GCE) was fabricated, and used to study the electrochemical reaction of ascorbic acid (AA). The oxidation current of AA increased nearly 6-times and the oxidation potential was negatively shifted compared with the bare GCE, which should be result from the large surface area and good charge transfer ability of BPNS film. Several impacting factors including the amount of modified BPNS, the pH value, and the potential scan rate, were investigated. Under the optimal condition, differential pulse voltammetry was used to detect AA in the range of 1–35 nM with a detection limit of 0.3 nM. The obtained results revealed the potential electrochemical sensing application of BP nanomaterials, which should promote the further analytical application of two-dimensional nanomaterials.
A Novel Electrochemical Sensor Based on Graphene Oxide Nanosheets and Ionic Liquid Binder for Differential Pulse Voltammetric Determination of Droxidopa in Pharmaceutical and Urine Samples
Droxidopa is a synthetic amino acid that undergoes conversion to the potent vasoconstrictor norepinephrine in the presence of aromatic amino-acid decarboxylase and pyridoxal phosphate. It is effective for the treatment of frozen gait and dizziness on standing associated with Parkinson’s disease and for the treatment of orthostatic hypotension. In the present work, the anodic oxidation of droxidopa at the surface of novel carbon paste electrode adjusted with ionic liquid (n-hexyl-3-methylimidazolium hexafluoro phosphate) and graphene oxide (GOILCPE) was studied. The structure of the modified electrode was examined via SEM. The electrochemical discernment of the modified electrode was conducted via cyclic voltammetry (CV), chronoamperometry (CHA) and differential pulse voltammetry (DPV). DPV demonstrates a linear response within the 1.0 × 10–7 to 6.0 × 10–4 M range for droxidopa. A detection limit of 3.0 × 10–8 M was obtained. Finally, the modified electrode was applied with success for the accurate detection of droxidopa content within real samples.
Regularities of Conductivity of Aqueous Molecular Solutions
The work presents the results of measurements of specific conductivity in aqueous solutions of low–molecular alcohols: mono-, di-, tri-, and nonaethylene glycols, glycerol, ethanol, sorbitol, and acetone in the full concentration range. It is shown that not only hydroxyl groups should be considered as the donor–active charge carrier centers in the studied systems, but also oxygen atoms, which is illustrated by a linear dependence of the conductivity maximum on the number of hydration centers. A new method of normalization of specific conductivity is suggested that allows extracting the component corresponding to the charge carrier donor.
Dispersion of Water Conductivity in the Frequency Range of 104–106 Hz
The frequency dependence of impedance is studied in a capacitance cell filled with water directly contacting the electrodes. The absolute impedance value is determined by measurement of voltages in the cell and over the known resistance connected in series with it. The impedance dispersion range is found in the range of 104–106 Hz, where it decreases from the maximum to the minimum values. The processing of the impedance data using the corresponding equivalent circuit shows that distilled water has a constant dielectric permeability value (78–80 a.u.) in the whole studied range of 50 Hz to 10 MHz and impedance dispersion is related to dispersion of conductivity of water. An expression is obtained for description of conductivity of water at low, intermediate, and high frequencies (0–100 MHz) analogous to the Debye relationship. The value of τ = 0.6 μs and the value of the limiting high-frequency conductivity of 3 mS/m (at 20–25°C) is found for the additional conductivity dispersion region.
Electrochemical Activity of Metal-Ion Exchanger Nanocomposites
The electroreduction of oxygen on thin-film metal–polymer nanocomposites that differ in the metal (Ag, Cu, Pd), content, particle size of the metal component, and ionic form of the Lewatit K2620 matrix (H+, Na+) was studied. The limiting oxygen diffusion current and effective number of electrons involved in oxygen electroreduction were determined. The limiting current and the number of electrons increased with the content of metal nanoparticles and transition to larger nanoparticles. The oxygen electroreduction occurs by the four-electron mechanism, whereby the hydrogen peroxide intermediate product does not accumulate, and oxygen is reduced directly to water molecules. The electrochemical reduction of the metal oxidation products and hydrogen evolution can be observed depending on the ionic form of the matrix.
De-Alloyed PtCu/C Catalysts of Oxygen Electroreduction
Platinum-containing bimetallic nanoparticles manifest high functional characteristics as electrocatalysts. To use PtCu/C catalysts in low-temperature fuel cells, it is necessary to minimize selective copper dissolution, as copper cations can pollute the polymer membrane and decrease its proton conductivity. The work determines the composition, measures the electrochemically active surface area, and studies the electrochemical behavior of PtCu/C catalysts containing nanoparticles with a “core–shell” structure in the initial state (as-prepared) and after pretreatment in solutions of different acids. The comparative determination of catalyst activity in an electrochemical cell and their testing in a membrane-electrode assembly of fuel cells showed that pretreated PtCu/C materials with a much better stability as compared to Pt/C were also noninferior to the latter as regards their activity in the oxygen electroreduction reaction.
New Solid Electrolyte Li8– xZr1 –xTaxO6 (x = 0–0.5) for Lithium Power Sources
In the work, new lithium-conducting solid electrolytes based on lithium zirconate are synthesized. They are obtained by doping Li8ZrO6 phase with isostructural Li7TaO6. It is shown that in the Li8– xZr1– xTaxO6 system, a series of solid solutions х = 0−0.5 based on Li8ZrO6 form. The conductivity of synthesized Li8 ‒ xZr1 – xTaxO6 solid solutions increases by 1–2 orders of magnitude as compared with undoped zirconate Li8ZrO6 due to the formation of lithium vacancies in the tetra- and octahedral layers of the structure. All-solid-phase electrochemical cells with Li7.85Zr0.85Ta0.15O6 electrolyte, 0.75Li2SnMo3O12 ∙ 0.25B2O3 glass-ceramic anode, and 0.2Li2O · 0.2LiF · 0.45V2O5 · 0.25B2O3 cathode are electrochemically tested. It is shown that the resistance of 0.75Li2SnMo3O12 · 0.25B2O3|Li7.85Zr0.85Ta0.15O6|0.2Li2O · 0.2LiF · 0.45V2O5 · 0.25B2O3 cell decreases after the charge—discharge cycling.
Effect of Additive DCTA on Electrochemical Tunnel Etching of Aluminum Foil
The effect of additive DCTA (1,2-diaminocyclohexane-tetraacetic acid) to HCl + H2SO4 solution on electrochemical tunnel etching behavior of aluminum foil was investigated. The results show that DCTA can activate Al foil surface by decreasing the self-corrosion potential and breakdown potential, which may be attributed to that DCTA forms chelate with dissolved Al3+, thus suppressing the oxide film formation. The tunnel density and effective tunnel number as well as uniformity of tunnel length of etching foil can be increased after DCTA addition. Furthermore, the specific capacitance of etching foil can be enhanced with trace addition of DCTA.
Oxygen Electroreduction on the Anthraquinone-Modified Thin-Film Carbon–Polymer Composite in Alkaline Solution
Technical carbon CH210 was processed by chemical reduction of the diazo derivative of anthraquinone for surface modification. The presence of anthraquinone groups on the carbon surface was confirmed by attenuated total internal reflection (ATR) IR spectroscopy. Carbon with the anthraquinone-modified surface was deposited on a glassy carbon support using a polymer binder. The behavior of the thus obtained catalyst in oxygen electroreduction in an alkaline medium was studied by the rotating disk electrode method. The kinetic characteristics of the reaction were determined: half-wave potential, limiting current, number of electrons, Tafel slope, exchange current, and charge transfer coefficient. Hydrogen peroxide is formed on the surface of the carbon–polymer composite at higher positive potentials than on technical carbon and glassy carbon electrodes. Therefore, the proposed material can be used as an effective electrocatalyst for this reaction.
Transport Properties of MF-4SK Membranes Doped with Sulfonated Zirconia
Composite materials based on homogeneous perfluorinated MF-4SK cation-exchange membranes and sulfonated zirconia are obtained by in situ and casting methods. Their transport properties and gas-permeability are studied. The introduction of sulfonated zirconia leads to increase the room-temperature conductivity of membranes obtained by the in situ and casting methods more than 1.5- and 4-fold, respectively. For composite membranes synthesized by the in situ and casting methods, the transport numbers of anions that characterize their undesired transport decrease more than 1.5-fold (from 0.026 to 0.020 and from 0.020 to 0.014, respectively). For samples based on MF-4SK membranes and zirconia, the considerable (more than 3-fold) decrease in hydrogen permeability is observed. The differences in the observed values of water uptake, conductivity, and interdiffusion coefficients in composite membranes are discussed.
Theory of Electrochemical Kinetics for Perovskite Solar Cells: Fitting Current–Voltage Curves
Based on the reaction of electron-hole separation in perovskite solar cells, we derived the mathematical relationship between current and voltage from the viewpoint of electrochemical kinetics and, moreover, by using this relation, we successfully fitted the i–E curves. We found that the nonlinear relationships between the activation energy and the potential of the recombination reaction are the fundamental reason for the appearance of the hysteresis loop.
Effect of Cl– and \({\text{SO}}_{4}^{{2 - }}\) Ions on Electrodeposition of Cobalt from Acidic Gluconate Solutions
A role of anions in potentiostatic electrodeposition of cobalt from acidic gluconate solutions was investigated. Equilibrium distribution of soluble species in the solutions was calculated and compared with absorption spectra. Cyclic voltammetry and potentiostatic measurements confirmed that cathodic process was inhibited mainly by free sulfate ions. Improved buffer capacity of gluconate baths by addition of sulfate ions protected against contamination of metal deposits by products of cobalt salt hydrolysis. Mathematical models of metal nucleation were tested indicating progressive mode responsible for the formation of the metal phase. Diffusion coefficients of cobalt species were also calculated using various approaches. Thickness, morphology and structure of cobalt deposits as well as cathodic current efficiency were also discussed.
Inhibitive Properties and Computational Approach of Organoselenides on Mild Steel Corrosion in Acidic Environment
The activity of organoselenides as corrosion inhibitors for mild steel (MS) in 1.0 M hydrochloric acid was evaluated via electrochemical, surface examination and computational chemical methods. The results revealed that the corrosion inhibition percentage (% IE) of organoselenides reached more than 80% with little concentration. Tafel curves showed that organoselenides act as mixed-type inhibitors. EIS measurements indicated that organoselenides mitigate MS corrosion by adsorption on the surface. SEM and AFM analysis depicted the significant improvement in the MS surface in the presence of organoselenides, protecting the surface owing to the formation of an inhibitive film over the metallic surface. Also, DFT computations were conducted on the active form of the investigated compounds. Results from the practical experiments and theoretical calculations suggested that organoselenides are promising inhibitor candidates for corrosion of MS in 1.0 M hydrochloric acid.
Effect of Copper Sulfate Concentration on the Electrochemical Nucleation Process, Growth and Properties of n-Type Cu2O Thin Films
Cu2O-n thin films were successfully electrodeposited from a Cu(II) lactate solution containing different concentrations of copper(II) sulfate (CuSO4) and 1 M lactic acid (C3H6O3) at pH 6.5. The electrochemical behaviour of Cu2O thin films has been investigated by means of cyclic voltammetry (CV), chronoamperometry (CA). The nucleation behaviour of the deposited Cu2O has been studied on FTO substrates as a function of Cu2+ concentration. It was found that the nucleation changes from progressive to instantaneous with increasing Cu2+ concentration. Many electrochemical parameters were investigated such as transfer coefficient, diffusion coefficient, cathodic and anodic charges, nucleation rate etc. The effect of the nucleation mechanism on microstructural and optical properties of Cu2O were investigated by X-ray diffractometry (XRD) and ultraviolet visible spectrophotometry (UV–Vis–NIR) and photoluminescence (PL). The optimal concentration of Cu2+ ions was found to be 0.075 and 0.1 M obtained with instantaneous nucleation process. The high photoluminescence (PL) efficiency observed indicating good optical properties with a high carrier density, small depletion layer, high photo-generated electron–hole pairs, narrow band gap and low charge transfer resistance. This results exhibit a high photoelectric performance.
The Mixture of Nanoparticles of RuO2 and Pt Supported on Ti as an Efficient Catalyst for Direct Formic Acid Fuel Cell
An active coating, composed of a mixture of nanocrystals of RuO2 with the rutile structure and nanocrystals of metal Pt, was thermally synthetized on a titanium substrate. Cyclic voltammograms and polarization curves showed that the catalytic activity of the coating for the formic acid oxidation in an acidic solution increased with an increase in the RuO2 content, reaching the maximum value at 50 mol % RuO2. Additionally, further increase in the RuO2 content resulted in a decline of the catalytic activity. The catalytic effect was attributed to a bifunctional mechanism and an electronic effect. The bifunctional mechanism had a dominant role and was based on the fact that Ru–OH species were formed on Ru atoms of RuO2 at more negative potentials than on Pt. Those species oxidized the adsorbed COad and HCOOad—species on adjacent Pt atoms of clusters of metal Pt and thus discharge them to oxidize new HCOOH molecules.
Determination of Sulfite in Wine Using Differential Pulse Polarography
Sulfite determination plays an important role, since it is used in some food stuff as protecting agent. It is a known fact that higher values of sulfite in foods will create some health problems. Thus, its accurate determination has a vital importance. In this investigation a new and simple DP polarographic method is established for the determination of sulfite. The polarographic peak of sulfite was used for its determination. The polarograms of sulfite were taken in various electrolytes and pH values in the presence or absence of wine in order to find the best working conditions. It was possible to determine 2 × 10–6 M sulfite in pH 4 Hac–NaAc electrolyte. This method is applied to various wines and it was possible to determine the free and bound sulfite. The results obtained were also compared with an iodometric method used in TSE (Turkish standardization Institute).
Catalyst-Free, Facile and Green Synthesis of New Symmetric and Asymmetric Benzofurans through Hydroquinones Oxidation in the Presence of Meldrum’s Acid
Electrochemical oxidation of hydroquinones (1a–1b) were studied in the presence of meldrum’s acid (3) as a nucleophile in an ethanol-phosphate buffer (pH 7, 0.20 M) mixture (as a green media), by means of voltammetric techniques. The obtained results indicated that the p-quinones (2a–2b) are derived from 1a–1b participation in a 1,4-Michael addition reaction, with the meldrum’s acid (3) to form the corresponding new symmetric and asymmetric benzofurans (8a and 6b). The electrochemical synthesis of these new compounds (8a and 6b) has been successfully performed in an undivided cell with high yield and good purity.
Evolution of the Electrochemical Reduction of Indium Tin Oxide in an Aqueous Solution of Silica Particles
Electrochemical reduction of indium tin oxide (ITO) in SiO2 solution was investigated by analyzing the properties of ITO and the reactant diffusion in ITO films. In the electrochemical system, an ITO anode and cathode were immersed in 1 wt % SiO2 solution (pH 6.8). The electrodes were set to 15 V at room temperature under different durations of electrochemical treatment. The properties of the cathodic ITO film were analyzed after treatment. The ITO films varied from transparent to black and gray during the treatment. In2O3 underwent reduction and transformed to In, as indicated by X-ray diffractometry. The surface morphologies of the ITO samples revealed that the ITO crystals were damaged. The damage resulted in numerous aggregated particles forming on the film surface after electrochemical treatment. The major elements of the particles were confirmed to be oxygen and In. The electrical resistance of the treated ITO considerably increased because of the damage to the In2O3 crystals. The simulation of the diffusion model and experimental results indicated that the electrochemical reaction rate of ITO was controlled by the reactant diffusion in the ITO film.
Remediation of Clayey Soil Contaminated with Copper Sulfate Using Washing-Enhanced Electrokinetics Technique
The present study focused on remediation of clayey soil contaminated with two percentages of copper sulfate using washing-electrokinetics technique enhanced by purging solutions and mid compartment. The intact soil samples are obtained from Al-Ahdab oil field located in the southeast of Iraq, where the soil samples are contaminated synthetically with two percentages of copper sulfate (6666.66 and 26666.66) ppm for 30 days. The electrokinetics technique enhanced with a mid compartment to reduce the exist way of contaminant from the soil. Also, it is enhanced by purging solutions in the anode, mid, and cathode compartments to control the pH value of solutions in the resvoirs. The activated carbon is used to prevent the reverse osmotic flow from cathode to anode. The main results of physical model are the variation of electrical current with time, pH value, and the accumulated volume of osmotic flow. Increasing the concentration of copper causes raising the electrical current generated during the remediation process, so the chemical reaction occurred in the anode, mid and cathode compartments are increased. The removal efficiency of copper from soil samples ranged 98.4 to 99.6%, which indicated high efficiency within short time, but using washing process causes a reduction in the time required for remediation by 30% and causes a slight increase in the removal efficiency.
Humidity Sensor Based on Orange Dye and Graphene Solid Electrolyte Cells
The fabrication and characterization of thin film humidity sensors based on orange dye (OD) and OD–graphene solid electrolytes cells were done in this paper. The 200 nm thick silver (Ag) and copper (Cu) electrodes were deposited on glass substrate by thermal evaporation. There was gap of 20 µm between the electrodes, where the 8 to 12 µm thick film of solid electrolyte was deposited. The pure OD and the OD–graphene composites with 40 and 60% (by weight) graphene were used as solid electrolytes. The dependences of the open-circuit voltage of the cells on humidity were measured in the humidity interval from 34 to 90% relative humidity (RH). It was found that with increase in humidity the open-circuit voltage of the cells increased. In the OD–graphene composite cells on increasing the concentration of graphene the open-circuit voltage increased accordingly.
Analysis of Potential Distribution at the Boundary with the Membrane inside a Flow-by Porous Electrode at Various Currents. Part I. Modeling
The potential profiles at the boundary with the ion-exchange membrane and near the current feeder and the current and concentration profiles of the target electroactive component along the solution flow in the galvanostatic mode are calculated at various current loads using a simplified model of porous electrode. From the analysis of the calculated results, it follows that the potential profiles vary significantly depending on the current and the presence or absence of a side reaction. The results can be used for preliminary estimation of electrolysis mode, which provides the highest efficiency of porous electrode operation.