Monophasic powders of the cubic modification and the nominal composition Li6.4Al0.2La3Zr2O12 (Al-LLZO) and Li6.52Al0.08La3Zr1.75Ta0.25O12 (Ta-LLZO) are synthesized. Dense (~97–98%) solid-electrolyte ceramic samples with enhanced stability in air are obtained from these powders using the method of spark plasma sintering. The high Li-ionic conductivity (4–6 × 10–4 S/cm) corresponding to the world level is achieved.
The thermal and electric properties of the Y3+-doped Ba7In5.9Y0.1Al2O19 phase with the hexagonal perovskite structure (a = 5.935(7) Å, c = 37.736(8) Å) are studied. It is shown that this phase can incorporate protons and exhibit protonic conduction. Upon addition of an isovalent dopant, yttrium, the concentration of protons increases (up to the limiting value for Ba7In5.9Y0.1Al2O19·0.55H2O), as a result of the increase in the unit cell volume and, correspondingly, in the free space for accommodating OH– groups in the oxygen-deficient block containing coordination-unsaturated polyhedrons [BaO9]. The isovalent doping increases the oxygen-ionic conductivity due to an increase in interatomic distances and a decrease in the activation energy of migration. In a humid atmosphere (pH2O = 1.92 × 10−2 atm), the Ba7In5.9Y0.1Al2O19 phase exhibits the higher values of protonic conductivity as compared with the matrix compound Ba7In6Al2O19 and below 500°C is characterized by the predominant proton transport both in air and in a wide pO2 region (10–18–0.21 atm).
Pt(WC1 – x)/Cu electrodes are obtained by depositing platinum onto the surface of tungsten carbides under open circuit conditions. A tungsten carbide layer with a thickness of ca. 20 μm is formed preliminarily on the surface of copper plates by the thermolysis of a gas mixture WF6 + H2 + C3H8. During the open-circuit deposition, platinum nanoparticles are formed on the surface of tungsten carbides. The oxidation of surface layers of tungsten carbides provides the electrons to reduce Pt(II) compounds. The morphology of thus prepared electrodes is studied using scanning electron microscopy (SEM). The chemical composition of the surface layers is studied using X-ray photoelectron spectroscopy (XPS). The phase composition is studied using X-ray phase analysis (XRD). The deposition of small amounts of platinum (0.002–0.24 mg Pt/cm2 of the geometric electrode surface) gives rise to a significant increase in the hydrogen evolution reaction (HER) rate. The catalytic activity for the sample loaded with 0.24 mg/cm2 platinum approaches that of a Pt/Pt electrode. The HER voltammetric characteristics on these Pt(WC1 – x)/Cu electrodes are determined. The hydrogen evolution is assumed to proceed on the catalytically active platinum nanoparticles.
The innovation of a flexible supercapacitor is the valuable establishment of conductive and charge storage materials into stretchy frameworks due to incorporating physical elasticity with the fundamentally high-power density of supercapacitors. Flexible supercapacitors have a lot of potential as power sources for next-generation flexible electronics since they are safer, more robust, and mechanically more stable than current batteries. This paper explains the construction of flexible cathode electrodes for supercapacitors made of EVA thermoplastic film, polyaniline, and carbon nanotubes. Herein, by combining Ethylene-vinyl acetate (EVA), Polyaniline (PANI)’s pseudo-capacitance, and the charge transport ability of carbon nanotubes (CNTs), EVA/PANI@CNT flexible films were constructed as supercapacitor cathode electrodes with brilliant electrochemical performance and elasticity. Electron beam irradiation at 100 kGy is used in crosslinking carbon nanotubes/polyaniline (PANI@CNT) composites with ethylene-vinyl acetate. These electrode materials were prepared with different concentrations of nanostructures (PANI@CNT) (50, 60, and 70%) concerning EVA thermoplastic film as a current collector. Then study the electrochemical performance of prepared conductive polymeric films without and with EBI at 100 kGy. The improvement in electrochemical performance of the flexible cathode electrodes is theoretically due to the creation of structural defects upon irradiation. Also, the structure, phase, and avascularity of as-prepared films were verified utilizing XRD, FTIR, and Raman. This study proves that optimizing the concentration of the electroactive material/current collector interface can apply faster electron transport and constitutes a powerful strategy to reinforce the electrochemical capacitive properties of supercapacitors.
In continuation of our systematic study of the mechanism of thiocyanogen generation via electrochemical oxidation of thiocyanate anion in acetonitrile, the influence of proton donors both on the generation and on the reactivity of thiocyanogen itself was studied by experimental (cyclic voltammetry, electrolysis) and theoretical (digital simulations, quantum chemical calculations) methods. In a series of acids of various strengths (acetic, trifluoroacetic and perchloric acids), the effect was revealed only in the case of a strong proton donor, perchloric acid. It was shown that perchloric acid forms with thiocyanogen a hydrogen-bonded complex, less active in the thiocyanation reaction.
The performance enhancement of proton exchange membrane fuel cells (PEMFCs) is directly correlated with water flooding, which is based on the design and operational parameters of the flow field. Flooding affects reactant distributions; hence, effective water management is necessary for optimizing the performance of PEMFCs. The present study, investigated the performance of PEMFCs by introducing a novel semicircular trap shape in the flow field, and assessed the effect of increasing the number of traps and the size of the trap shape. The introduction of the trap shape in the flow field, reduces the land width at the location of the bipolar plate. This reduced land width increases the current density per unit of active area. Therefore, figuring out the perfect size and quantity of traps is essential to improving PEMFC efficacy. The results show that a channel with a single trap shape of 2.0 mm width and 1.0 mm height provide higher current density. The trap shapes improve reactant distribution, effective water management and enhance the power density. This novel trap shape can be implemented in a conventional channel providing an inexpensive solution to enhance PEMFC performance.
An approach of the preparation of catalysts based on copper oxide-polypyrrole (PPy) composites formed via electrooxidation of CuI–PPy layers on the surface of inert glassy carbon electrode was proposed. The pure CuI without polypyrrole matrix was used for comparison. The formation of CuO and the presence of CuO phase in electrooxidized samples was confirmed by EDX and XRD analysis correspondingly. Electrochemical properties of electrooxidized CuI–PPy composite (EOCP) were studied in formaldehyde and methanol oxidation reactions and compared with electrochemical properties of electrooxidized CuI (EOC) sample. Tests in methanol and in formaldehyde solutions confirmed the highest sensitivity of studied samples to formaldehyde. The linear detection range (LDR) of formaldehyde detection in alkaline solution for EOC system was 0–10 mM, the sensitivity was 125 ± 4 nA µg–1 mM–1, the detection limit was 15.9 ± 0.6 µM, while EOCP system demonstrated the extended LDR of 0–60 mM, the slightly lower sensitivity of 103 ± 0.5 nA µg–1 mM–1 but the lower detection limit of 7.3 ± 0.3 µM.
This review investigated the literature, mainly of recent years, on the current topic of using graphenes in supercapacitors. The effects of the graphene porous structure, doping, and irradiation are considered. Methods for producing graphenes, composites of graphenes with metal oxides, sulfides, and selenides, metal particles, electron-conducting polymers, MXenes, as well as quantum dots, are considered. Electrochemical characteristics are given for the considered graphene types.
A recently proposed express method for experimental determination of diffusion coefficients of electrotive ions inside a membrane and their distribution coefficients at the membrane/solution interface (Russ. J. Electrochem., 2022, vol. 58, p. 1103) is based on the comparing of a measured non-stationary current across the electrode/membrane/electrolyte solution system upon applying a potential step with theoretical expressions for the time dependence of the current, the steady-state regime being included. In previous publications, the application of this method to the studies of the bromide anion transport across membrane is carried out under conditions of the membrane selective permeability (permselectivity) for non-electroactive counter-ions where the electrical field intensity inside it has been suppressed by their high concentration. Under this condition, the movement of electroactive co-ions (bromide anions), having a much lower concentration inside the membrane, takes place via the purely diffusion mechanism, for which analytical solutions have been available. When the concentrations of electroactive co-ions and supporting-electrolyte counter-ions inside the membrane are comparable, their transport is contributed by both diffusion and migration. In particular, such a situation takes place in a ternary system of monovalent ions where both ions of the supporting electrolyte M+ and A–, as well as the electroactive anion X–, penetrate the membrane from the external solution, their concentrations inside the membrane appeared being comparable. In this work, we derived analytical expressions for the steady-state distributions of the concentrations of all ionic components, as well as of the electrical field, inside the membrane as a function of the amplitude of the passing stationary current and of the ion concentrations in the bulk solution, as well as for the diffusion–migration limiting current density. In particular, it is shown that at a low concentration of co-ions at the membrane/electrolyte solution interface [compared to the concentration of fixed charged groups of the membrane: Xm ( ll ) min (Cf, Mm)], the migration contribution into the flux of electroactive ions can be neglected. On this reason, the formulas derived in this work for the ternary electrolyte are reduced approximately to the corresponding expressions for the pure diffusional transport. If the opposite condition is fulfilled (Xm/Cf ( gg ) 1), the migration contributions into the ion fluxes lead to a modification of the expression for the diffusion–migration limiting current.
Electrochemical noise analysis (ENA) is performed on lithium cobalt oxide (LiCoO2) ICR 18650 commercial lithium-ion batteries. The interest of ENA lies in its potential for passive diagnostics during the charging and discharging of the battery. The electrochemical noise of the batteries is characterized by two methods: power spectral density (PSD) and standard deviation (STD). Good reproducibility of the results has been demonstrated. All power spectral analyses highlight the same shape and robust signature. The obtained spectra show a classical fractional power frequency dependence (1/f α) at low frequency (0.1 < f < 1 Hz) and a plateau at very-low frequencies (less than 0.1 Hz). On one hand, the beginning (from SOC 100 to 84%) and end (SOC < 16%) zones are characterized by a PSD slope α ≈ 2. On the other hand, the middle zone (16 ≤ SOC < 84%) is characterized by a PSD slope α < 2. The obtained STD curves have a V-shape form with the minimum value occurring near 38% of SOC, corresponding to minimum slope α = 1.2. Furthermore, the end and beginning zones exhibit significantly higher PSD amplitude (PSD(f → 0)) and STD compared to the middle zone. There are promising results regarding the potential for determining the state of health of the battery, but aging campaigns still need to be carried out.
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