Russian Journal of Electrochemistry最新文献

We demonstrated a mechanochemically-assisted approach to synthesize Ti₃C₂T_x MXene with crinkled morphology with enhanced energy storage performance. The fabrication efficiency and capacitive property of the resulting Ti₃C₂T_x MXene was significantly promoted under the aid of a high-energy ball mill: (i) removal of Al from pristine Ti₃AlC₂ powder was achieved after 8 h of etching in 2% hydrochloric acid, while 18 h was sufficient in 5% hydrochloric acid for conventional experimental as reported in previous literature; (ii) the capacitive property of the as-prepared samples increases with etching time, the 8-h mechanochemically etched sample showed a specific capacitance of 129 F/g at 10 mV/s in 1 M H₂SO₄ electrolyte, while no typical energy storage behavior was found for the sample without mechanochemical aid. The contribution of double layer, pseudocapacitive and diffusion-limited capacitance for the total specific capacitance was quantitively analyzed for the first time. The as-prepared sample exhibits higher specific capacitance than the previously reported MXene and MXene-based composites. The mechanochemically-assisted approach showed good capability in preparing Ti₃C₂T_x MXene with enhanced capacitive property.

A novel Fe(II) detection method was developed on nanopore platform in this work. The incubation mixture of dumbbell DNA and Bleomycin (BLM) wounld produce blockage signals on nanopore sensor. The addition of Fe(II) would generate BLM·Fe(II) to destroy the dumbbell DNA molecules and release short-strand oligonucleotide fragments which can produce spiked current signals on nanopore sensor. The statistical analysis shows the intervals between adjacent blockage signals decrease with elevated concentration of Fe(II), and a linear relationship between the event intervals versus the Fe(II) concentration is confirmed in the range of 0.1 to 500 nM with detection limit as low as 0.12 nM. Varied kinds of metal ions were examined for comparison, demonstrating high selectivity for Fe(II) detection. The proposed method may be potentially applied for qualitative and quantitative detection of Fe(II) due to its high sensitivity and selectivity.

In this work, we studied the effect of additions of decahydronaphthalene (decalin) and its derivative, perfluorodecalin (octadecafluorodecalin) on the lithium metal deposition and dissolution, in particular, the dendrite formation, at the anodes of lithium secondary power sources in an electrolyte based on lithium hexafluorophosphate in the mixture of ethylene carbonate and diethyl carbonate. The study was carried out using the methods of current transients and electrochemical impedance. The results showed that, in contrast to traditional cationic surfactants cetyltrimethylammonium bromide and hexadecylpyridinium bromide, which we have studied earlier, the decalin and perfluorodecalin demonstrated specific interaction with the surface of the lithium electrode. Moreover, the interaction with decalin is so strong that it actually blocks the processes of both lithium deposition and anodic dissolution at the surface of the lithium electrode. The interaction of perfluorodecalin with the lithium surface turned out to be weaker. As a result, perfluorodecalin does not interfere with the cycling of the lithium-metal anode, but at the same time shows an inhibitory effect on the dendrite formation. In the electrolyte added with perfluorodecalin, the lithium anode was able to undergo more than 80 charging–discharging cycles with a Coulomb efficiency of 70–80%, while without the additive, the number of cycles was less than 40, and the Coulomb efficiency was 60% or lower.

Cu-doped polyaniline (Cu–PA) was prepared by chemical oxidation aniline in the presence of Cu ions. By cyclic voltammetry (CV), the electrochemical behavior of glassy carbon electrode modified with Cu–PA was studied in NaOH solution. Since the hydrolysis of glucose occurs in an alkaline solution and the redox peak of Cu–PA depends on the concentration of OH^– concentration, here, a new and cost-effective strategy for the non-enzymatic determination of glucose was proposed based on the inhibitory effect of glucose on the electrical activity of the Cu–PA composite. The cathodic current decreased directly after the addition of glucose and demonstrated that the Cu–PA was sensitive to glucose in an alkaline medium. Using linear sweep voltammetry and under optimal condition, the sensor exhibited a linear calibration graph in the concentration range of 0.11–1.66 mM with a limit of detection (LOD) of 0.044 mM (S/N = 3). In addition, the sensor showed desirably accurate selectivity for detecting and recovering glucose in humans serum samples, good reproducibility, and good stability.

This study aimed to develop an electrochemical sensor based on a derivative of graphene oxide (GO) and a molecularly imprinted polymer (MIP) on a pencil graphite electrode (PGE) for the detection of ascorbic acid (AA). MIP was fabricated onto the surface of the electrode by electropolymerization technique using cyclic voltammetry with a scan rate of 10 mV/s consisting of template molecule (ascorbic acid), functional monomer (polypyrrole), cross-linker (LiClO₄) and citrate buffer at pH 4. Then, the template removal process was conducted to create the imprinted cavities for detecting the analyte. Differential pulse voltammetry (DPV) and cyclic voltammetry (CV) methods were used to perform quantitative analyses of the modified electrodes. CV analysis was performed at the optimum scan rate of 10 mV/s, and the electrolyte concentration at 1.0 mM K₃[Fe(CN)₆] in 0.1 M KCl. MIP-PGE (2) produced the best performance by having the highest redox peak current response when scanning with the CV compared to other modified electrodes. The optimum parameters for DPV measurement are 100 mV pulse amplitude, 200 ms pulse period, and 10 mV/s scan rate. The straightforward instrumentation and easy preparation of the proposed sensor make it a valuable system for constructing simple devices for determining ascorbic acid.

The effect of pluronics L61 and F68 containing hydrophobic poly(propylene oxide) blocks of the same length and hydrophilic poly(ethylene oxide) blocks of different lengths on the conductance of planar bilayer lipid membranes made of azolectine is investigated. The conductance of these membranes increases as the concentration of both pluronics increases. For the same concentration of pluronics in solution, the conductance is higher for L61. Based on the literature data, the concentration of pluronics bound with the bilayer is calculated. For the close concentration of membrane-bound pluronics, the conductance of membranes is also close. It is concluded that in the first approximation, the appearance of the same hydrophobic parts of pluronics L61 and F68 in a membrane is accompanied by the same increase in its conductance. The conductance vs. concentration curves are superlinear for L61 and sublinear for F68. In the presence of either of these pluronics, the conduction spikes with the amplitude from 10 to 300 pSm and higher are observed for approximately 40% of membranes. These surges of conductance are associated with the appearance of conductive pores or defects in the membrane. The number of pores observed in the membrane is a random variable with a large scatter and does not correlate with the pluronic concentration. The difference between the average pore conductivities for membranes containing L61 and F68 is statistically insignificant.

The goal of this work is to confirm our earlier conclusion that the regularities observed during the electrodeposition of metallic lithium on copper and lithium electrodes can be associated with differences in the properties of the so-called solid electrolyte interphase formed at these electrodes in contact with the electrolyte. To do this, we analyzed the electrochemical impedance spectra measured during the above processes by using the method of the distribution of relaxation times. The electrolyte addition with surfactants (the cetyltrimethylammonium bromide and hexadecylpyridinium bromide) was shown to lead to a significant change in the properties of the solid electrolyte interphase layers and a noticeable increase in the values of the impedance components associated with the Faradaic processes at these electrodes. This indicates an inhibition of the lithium electrodeposition processes and the related process of dendrite formation under these conditions. At the same time, no such impedance components were observed at the fresh-formed deposit, which confirms our earlier conclusion that the effects of surfactants on the dendrite formation are associated with the changes in the properties of the solid electrolyte interphase layers in the presence of the surfactants, rather than the surfactants’ adsorption at lithium and blocking of the dendrite growth.

The processes at platinum electrodes during the cathode polarization in an alcohol solution of erbium nitrate are discussed. The current density maxima on the cathode branch of voltammograms were found to correspond to the potentials of the hydrogen reduction reactions. The gel-like deposit Er(OH)_x(NO₃)_y(С₂Н₅О)_z·nH₂O, x + y + z = 3, formed during the cathode treatment was shown to be not a product of the electron exchange between the cathode and the solution components. The following formation mechanism of the erbium-containing deposit has been suggested. First, the electrochemical process of the hydrogen cathode reduction is implemented. This process leads to the ionic unbalance and causes the alkalinization of the cathode space. This creates conditions for the chemical process of the gel-like erbium hydroxide formation, which is physically adsorbed on the cathode surface as a precipitate.

The aim of this work is to study the possibility of suppressing the metallic lithium dendrite formation during the operation of lithium secondary batteries, including those with a metallic lithium anode. The electrochemical deposition of lithium on copper and lithium substrates in the presence or absence of two surfactants, cetyltrimethylammonium bromide and hexadecylpyridinium bromide, is studied by the current transient and electrochemical impedance measurements. A typical lithium-ion battery electrolyte based on lithium hexafluorophosphate in the mixture of ethylene carbonate and diethyl carbonate is used. The presence of the so-called SEI (solid electrolyte interphase) layer on the electrode surface is shown to have a significant effect on the electrodeposition process. It is also shown that the mechanism of lithium electrodeposition on copper and lithium substrates is different. It can be assumed that the observed effect of surfactants on the dendrite formation is associated not with the adsorption of surfactants on lithium and blocking the growth of deposits, but with the surfactant effect on the properties of the SEI layer formed at these substrates.

We developeda facile method to construct flexible, freestanding three dimensional hierarchical electrodes that consist of graphene encapsulated one-dimensional conducting polyaniline (PANi)@MnO₂ coaxial nanowires grown on electrospun carbon nanofibers (denoted as G-PANi@MnO₂/ECNFs). A combination of XRD, SEM, and TEM techniques were used to characterize the structures of G‑PANi@MnO₂/ECNFs. Electrochemical measurements confirmed that such nanostructured composites possessed higher electrochemical capacitance than that of each individual component due to synergistic effects. The G-PANi@MnO₂/ECNFs electrode exhibited extremely high specific capacitance (1364.3 F/g at 0.3 A/g) and superior cycling stability (89.2% retention rate after 2000 cycles) in a 1 M Na₂SO₄ aqueous solution. The excellent electrochemical performance of such nanoscale architectured electrodes provides a new route to develop flexible, freestanding, and high-performance supercapacitors.