Cathodic Linear Sweep Voltammetry Research Articles

Solidification of a Silica-Based Solid Composite Electrolyte for Lithium-Ion Batteries Induced By UV Irradiation

The use of solid electrolytes in lithium-ion batteries (LIBs) instead of their liquid counterparts may significantly increase their energy density. Of particular interest are solid composite electrolytes (SCEs) which can be synthesized by incorporating ionic liquids (ILs, salts with a melting point lower than 100 °C) into a solid matrix. This class of SCE can have a wide electrochemical stability window and is typically non-flammable.Chen et al.1 developed an SCE with excellent ionic conductivity, consisting of a mesoporous silica monolith which encloses an IL electrolyte (solid nanocomposite electrolyte or nano-SCE). It is formed from a precursor solution which does not contain acids such as formic acid or HCl, meaning that it can be impregnated into porous electrodes without causing damage to the latter. However, its gelation process is long and variable (5-9 days), and is considerably affected by its presence within the electrode. As such, the nano-SCE has poor manufacturability and is not compatible with the continuous roll-to-roll processing typically used for LIB manufacturing. The manufacturability of the nano-SCE can be significantly improved by making its solidification process instantaneous upon subjection to an external trigger.As such, organic modification was used to produce silica-based precursor solutions capable of triggered solidification, for instance by irradiation with UV light. This solidification process takes a few minutes to complete and does not depend on pH, rendering it particularly versatile. The aging of the precursor solutions was studied with 29Si, 1H, and 13C NMR spectroscopy, which revealed that the alkoxysilane precursor molecules condensed into larger soluble structures over the course of five weeks. The aged precursor solutions remained stable over an indefinite period of time. When a photo-initiator is added to these solutions and they are irradiated with UV light, the soluble structures are linked together, resulting in the formation of silica nanoparticles which subsequently aggregate into a porous matrix which encapsulates the ionic liquid electrolyte (ILE).The adaptation does not compromise the functional properties such as ionic conductivity or electrochemical stability. As determined with Raman spectroscopy, the extent of organic modification and amount of ILE can be optimized to decrease the interaction of lithium ions with the other ions as compared to the neat ILE. The increased Li+ mobility means that the SCE can reach higher ionic conductivity (2.7 mS cm-1 at 20 °C) values than the neat ILE (2.5 mS cm-1). Anodic and cathodic linear sweep voltammetry in three-electrode cells was performed to determine that the SCEs can have an electrochemical stability window exceeding 5 V (i.e. lithium plating < 0 vs Li+/Li and electrolyte oxidation > 5.0 V vs Li+/Li). Electrochemical impedance spectroscopy further confirmed the SCE’s compatibility with lithium metal. As no acids are added to the precursor solution, a good electrode compatibility is expected. As such, the precursor solutions were impregnated into NMC622-based electrodes, solidified, and incorporated in half cells. These cells had an initial discharge capacity of 162 mAh g-1 at 0.1 C, retaining 86.8% of this capacity after 100 cycles.This work was supported by funding from the European Union’s Horizon 2020 research and innovation program for the Solidify project under grant agreement No. 875557.(1) Chen, X.; Put, B.; Sagara, A.; Gandrud, K.; Murata, M.; Steele, J. A.; Yabe, H.; Hantschel, T.; Roeffaers, M.; Tomiyama, M.; et al. Silica Gel Solid Nanocomposite Electrolytes with Interfacial Conductivity Promotion Exceeding the Bulk Li-Ion Conductivity of the Ionic Liquid Electrolyte Filler. Sci. Adv. 2020, 6 (2). https://doi.org/10.1126/sciadv.aav3400.

Solution‐Processed GaSe Nanoflake‐Based Films for Photoelectrochemical Water Splitting and Photoelectrochemical‐Type Photodetectors

AbstractGallium selenide (GaSe) is a layered compound, which has been exploited in nonlinear optical applications and photodetectors due to its anisotropic structure and pseudodirect optical gap. Theoretical studies predict that its 2D form is a potential photocatalyst for water splitting reactions. Herein, the photoelectrochemical (PEC) characterization of GaSe nanoflakes (single‐/few‐layer flakes), produced via liquid phase exfoliation, for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in both acidic and alkaline media is reported. In 0.5 m H2SO4, the GaSe photoelectrodes display the best PEC performance, corresponding to a ratiometric power‐saved metric for HER (Φsaved,HER) of 0.09% and a ratiometric power‐saved metric for OER (Φsaved,OER) of 0.25%. When used as PEC‐type photodetectors, GaSe photoelectrodes show a responsivity of ≈0.16 A W−1 upon 455 nm illumination at a light intensity of 63.5 µW cm−2 and applied potential of −0.3 V versus reversible hydrogen electrode (RHE). Stability tests of GaSe photodetectors demonstrated a durable operation over tens of cathodic linear sweep voltammetry scans in 0.5 m H2SO4 for HER. In contrast, degradation of photoelectrodes occurred in both alkaline and anodic operation due to the highly oxidizing environment and O2‐induced (photo)oxidation effects. The results provide new insight into the PEC properties of GaSe nanoflakes for their exploitation in photoelectrocatalysis, PEC‐type photodetectors, and (bio)sensors.

Preparation and Investigation of Silver Nanoparticle⁻Antibody Bioconjugates for Electrochemical Immunoassay of Tick-Borne Encephalitis.

A new simple electrochemical immunosensor approach for the determination of antibodies to tick-borne encephalitis virus (TBEV) in immunological products was developed and tested. The assay is performed by detecting the silver reduction signal in the bioconjugates with antibodies (Ab@AgNP). Here, signal is read by cathodic linear sweep voltammetry (CLSV) through the detection of silver chloride reduction on a gold–carbon composite electrode (GCCE). Covalent immobilization of the antigen on the electrode surface was performed after thiolation and glutarization of the GCCE. Specific attention has been paid to the selection of conditions for stabilizing both the silver nanoparticles and their Ab@AgNP. A simple flocculation test with NaCl was used to select the concentration of antibodies, and the additional stabilizer bovine serum albumin (BSA) was used for Ab@AgNP preparation. The antibodies to TBEV were quantified in the range from 50 IU·mL−1 to 1600 IU·mL−1, with a detection limit of 50 IU·mL−1. The coefficient of determination (r2) is 0.989. The electrochemical immunosensor was successfully applied to check the quality of immunological products containing IgG antibodies to TBEV. The present work paves the path for a novel method for monitoring TBEV in biological fluids.

Ni-P/Zn-Ni compositionally modulated multilayer coatings – Part 1: Electrodeposition and growth mechanism, composition, morphology, roughness and structure

The Ni-P/Zn-Ni compositionally modulated multilayer coatings CMMCs were electrodeposited from a single bath by switching the cathodic current density. The composition, surface morphology, roughness, layers growth pattern as well as the phase structure of deposits were extensively studied via SEM, EDS, AFM and XRD analysis. Effects of bath ingredients on the electrodeposition behavior were analyzed through cathodic linear sweep voltammetry. Although the concentration of Zn2+ in bath was 13 times higher than Ni2+, the Zn-Ni deposition potential was much nearer to Ni deposition potential rather than that of Zn. Addition of NaH2PO2 to the Ni deposition bath considerably raised the current density and shifted the crystallization potential of Ni to more nobble values. Codeposition of P with Zn-Ni alloy lead to crack formation in the monolayer that was deposited in 60 mA/cm2. However, the cracks were not observed in the Zn-Ni layers of multilayers. Zn-Ni layers in CMMCs exhibited a three-dimensional pattern of growth while that of Ni-P layers was two-dimensional. Also, the Ni-P deposits tends to fill the discontinuities in Zn-Ni layers and performed leveling properties and lowered the surface roughness of Zn-Ni layers and CMMCs. Structural analysis demonstrated that Ni-P layers were amorphous and the Zn-Ni layers exhibited crystallite phase of Zn11Ni2. Thus, the Ni-P/Zn-Ni CMMCs comprised of alternate layers of amorphous Ni-P and nanocrystalline Zn Ni.

Mechanism and kinetics of the electrocatalytic hydrogenation of furfural to furfuryl alcohol

The side reactions for the electrocatalytic hydrogenation of furfural are related to the type of catalyst. This paper reports the mechanism including the reaction process and rate determining step of the hydrogen evolution reaction (HER) at seven kinds of electrodes (Cu, Pb, Ni, Fe, Pt, Ti, Graphite) in 0.1M Na2CO3-NaHCO3 buffer solution (pH=10). The sequences of exchange current density and overpotential for the HER at different electrodes were determined. In particular, the mechanism and kinetics of the electrocatalytic hydrogenation of furfural at those electrodes were analyzed by cathodic linear sweep voltammetry in the presence of furfural. Current efficiency and selectivity were obtained by potentiostatic electrolysis. It shows that the optimal electrode for the reduction of furfural is Cu electrode. The HER at Cu electrode is only a bit easier than that at Pb electrode. However, the generation of carbon free radicals at Cu electrode is the easiest, and the selectivity towards the formation of furfuryl alcohol at Cu electrode is the highest among those electrodes. The results offered some guiding significance how to choose the optimal electrocatalyst for the catalytic hydrogenation of furfural.

Fabrication and magnetic properties of novel rare-earth-free Fe-Mn-Bi-P thin films by one-step electrodeposition

A novel Fe-Mn-Bi-P alloy film has been obtained by electrodeposition, and its structural and morphological features were characterized. Cathodic linear sweep voltammetry was used to study the electrodeposition behaviors of the alloy. The X-ray diffraction analysis demonstrates that the as-deposited and annealed Fe-Mn-Bi-P thin films consist of low-temperature-phase MnBi, Mn2Bi, and Fe3Mn7 phases. The as-deposited alloys exhibit the characteristic features of a soft magnetic and paramagnetic material. The coercivity of the annealed film was higher due to inter-diffusion reactions, structural relaxation, and the reduction in size and defects. The coercivity of the annealed film arrived at 53.4kA/m measured at 60K because of magnetocrystalline anisotropy.

Influence of electronic and optical properties of GaN nanoparticles as potential electrocatalyst in hydrogen production

Due the high electron density of the anion lattice found in nitrides, these compounds have been used for such applications as high power devices, photonics and, more recently, hydrogen production. Among nitride compounds, GaN is well known for its thermal stability, while the different physical techniques used for its synthesis have been reported to obtain different physicochemical properties. However, these techniques are not designed for the mass production of GaN. For these reasons, two different methods for both the chemical synthesis of GaN and its physical chemical characterization are reported in this study, with both synthesis methods presenting wurtzite phase crystallization. Furthermore, both samples presented agglomerates formed by similar sized nanoparticles (~20nm). Despite the similarity in the particle size, higher pore volume and surface area as well as carbon traces are promoted by the solvothermal route. In contrast, structural and photoluminescence (PL) characterization revealed that Ga vacancies and interstitial N formed in those samples synthesized by the nitridation method, promoting higher intensity in ~2.8eV PL band. Finally, based on cathodic linear sweep voltammetry, the samples prepared in this study can be considered good candidates for use in hydrogen production.

Substrate and electrode potential affect electrotrophic activity of inverted bioanodes

Electricity-consuming microbial communities can serve as biocathodic catalysts in microbial electrochemical technologies. Initiating their functionality, however, remains a challenge. One promising approach is the polarity inversion of bioanodes. The objective of this study was to examine the impact of bioanode substrate and electrode potentials on inverted electrotrophic activity. Bioanodes derived from domestic wastewater were operated at −0.15V or +0.15V (vs. standard hydrogen electrode) with either acetate or formate as the sole carbon source. After this enrichment phase, cathodic linear sweep voltammetry and polarization revealed that formate-enriched cultures consumed almost 20 times the current (−3.0±0.78mA; −100±26A/m3) than those established with acetate (−0.16±0.09mA; −5.2±2.9A/m3). The enrichment electrode potential had an appreciable impact for formate, but not acetate, adapted cultures, with the +0.15V enrichment generating twice the cathodic current of the −0.15V enrichment. The total charge consumed during cathodic polarization was comparable to the charge released during subsequent anodic polarization for the formate-adapted cultures, suggesting that these communities accumulated charge or generated reduced products that could be rapidly oxidized. These findings imply that it may be possible to optimize electrotrophic activity through specific bioanodic enrichment procedures.

Electrochemical deposition of nanodendritic Sn/Cu6Sn5 foam

Network structured porous foam with nano-sized dendrites was fabricated by co-electrochemical deposition of Cu and Sn. The foam, obtained in a Sn precursor-rich electrolyte, exhibited the open porous structure with a few hundred micrometer-sized spherical pores, while the pore wall was composed of nano-dendrites. The nano-dendrites were a mixture of Sn and Cu6Sn5, and the Cu6Sn5 alloy was embedded on the Sn dendrites. The cathodic linear sweep voltammetry of the electrochemical deposition indicated that the formation of Cu6Sn5 alloy was accompanied with Sn deposition, which reduced the foam deposition rate and resulted in the Sn/Cu6Sn5 nano-dendrites.

Mechanism of formation of anodic excursion peaks on lead electrode in sulfuric acid

Potential step and linear sweep voltammetry are proposed in combination for the anodic excursion peaks (AEPs) measurement of lead in sulfuric acid during cathodic scanning in the positive potential range. The overall procedure of measurement is composed of three steps. The first one is to polarize the lead electrode with negative potential, which is necessary for passivated PbSO 4(O) formation. Then, the polarization potential is stepped to positive to make sure that pure Pb could be oxidized to produce PbO n intermediate. Finally, a low-rate cathodic linear sweep voltammetry measurement is conducted in a small potential range. Four AEPs have been observed without reduction of PbO 2 to PbSO 4, which is in confliction with the conventional understanding that AEPs would appear accompanying with a large reduction peak for PbO 2 discharge. A new mechanism is therefore proposed that AEPs corresponds to the oxidation of PbO n intermediate in the cathodic scanning, so AEPs can be used to indicate the difficulty for the oxidation of Pb to PbO 2, and could be applied to characterize the corrosion resistance of lead alloy grid in the positive plate of a lead-acid battery.

Effect of water and oxygen traces on the cathodic stability of N-alkyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide

Although research in the field of ionic liquids for electrochemical applications has led to a deeper knowledge in their electrochemical properties, doubts in the interpretation of the experimental results are still encountered in the literature due to the poor control of the experimental conditions and/or to the limited number of experiments conducted. In this work, the effect of water and oxygen traces on the cathodic stability window of hydrophobic, air-stable ionic liquids composed of N -alkyl- N -methylpyrrolidinium (PYR 1A + ) cations and bis(trifluoromethanesulfonyl)imide (TFSI − ) anion, is reported. The extensive investigation performed by linear sweep voltammetry (LSV) and cyclic voltammetry (CV) indicates that the TFSI − anion is cathodically stable if the ionic liquid is pure and dry. The N -alkyl- N -methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquids investigated showed featureless cathodic linear sweep voltammetry curves before the massive cation decomposition took place at very low potentials.

Study of adsorption of citrate on Pt by CV and EQCM

Citrates are frequently used as additives in the electrodeposition of metals such as manganese in order to improve deposit characteristics and process efficiency. Nevertheless, few studies have been reported on the mechanism of citrate adsorption. This paper presents the results of a study of citrate adsorption onto platinum from solutions of various citrate concentrations in 0.1 M HClO 4. Simultaneous observations with an electrochemical quartz crystal microbalance (EQCM) and cyclic voltammetry (CV) indicate that with increasing concentrations, up to 10 −2 M, the fractional surface coverage by citrate rises to 13% in the region of hydrogen UPD, and the anodic formation of PtO is inhibited and reduced by as much as 43%. Combination of EQCM with cathodic linear-sweep voltammetry shows the interactions of citrate with platinum oxidation and hydrogen UPD. Thus, this approach reveals changes in additive adsorption with potential and indicates in particular the influence of the additive on the adsorption and desorption of hydrogen as a step in understanding metal deposition.

On the Chemical and Electrochemical One-Electron Reduction of Peroxynitrous Acid

Peroxynitrous acid was reduced by cathodic linear sweep voltammetry at a gold electrode and by iodide at pH 3.2 and 5.6. The cathodic reduction wave was identified by measuring its decay in time, which was the same as observed by optical spectroscopy. The iodide oxidation was followed by optical measurement of the triiodide formation. Both reductions show one-electron stoichiometry, with the product n(alpha)alpha = 0.23 +/- 0.04 from the electrochemical experiments, in which alpha is the transfer coefficient and n(alpha) the number of electrons transferred, and an diiodine yield of ca. 0.5 equiv per equivalent of peroxynitrous acid. The voltammetric reduction was irreversible up to scan rates of 80 V s(-1). Both reductions were pH independent in the range studied. The voltammetric reduction is most likely an irreversible elemental reaction followed by a chemical decay that cannot be observed directly. Because of the pH independence, we conclude that both reductions have a common short-lived intermediate, namely [HOONO]*-. We estimate the electrode potential of the likely ONOOH/ONOOH*- couple to be larger than 1 V. The commonly used electrode potential E degrees (ONOOH, H+/NO2*, H2O) does not describe the chemistry of peroxynitrous acid.

Indirect measurement of brucine by adsorptive stripping voltammetry at mercury electrode

After reaction with nitric acid, brucine can be transformed into cacotheline, and then measured indirectly by adsorptive stripping voltammetry. This method is based on the adsorptive accumulation of cacotheline at a hanging mercury drop electrode, followed by cathodic linear sweep voltammetry. The cathodic peak potential is about −0.35 V (vs. saturated Ag AgCl ). The detection limit of 2.0 × 10 −9 M is obtained under optimized conditions. The electrochemical behaviour of cacotheline and the mechanism of the electrode reactions are discussed.

Silver ion-exchanged zeolite modified electrodes: observation of electrochemically distinct silver ions

In this paper the electrochemical response of electrodes modified with silver ion exchanged Y type zeolites is examined. The cyclic voltammograms for the fully exchanged materials resemble closely those observed previously for silver mordenite zeolites. At low exchange levels (<10%, i.e., <5.6 silver ions per unit cell) cathodic linear sweep voltammetry indicates the presence of two electrochemically distinct silver ions

Adsorptive stripping voltammetry of Ni(II) using fast linear sweeps

Nickel was determined as bis-(dimethylglyoximato)-nickel(II) by fast cathodic linear sweep voltammetry with a rate of 10 V s−1 after adsorption on a static mercury electrode. The peak width at half-height was 60 mV. For determinations down to 1 ppb of Ni(II), only 40 s accumulation time were required without accelerating measures like stirring or potential application. Resolution and sensitivity were thus similar to differential pulse voltammetry but the duration of a measuring cycle was only 45 s (40 s accumulation, 80 ms for sweep and 5 s for readout). The method was tested with 2 industrial waste water samples and urine. The direct determination of Ni(II) in urine failed, whereas it was possible in the waste water. Concurrent adsorption was the main interference.

The effect of prolonged white light illumination on the anodic passivation of lead in sulphuric acid

The anodic potentiostatic oxidation of lead electrodes in aqueous sulphuric acid at 0.4, 0.6 and 0.8 V vs. a Hg/Hg2SO4 external reference electrode was examined under conditions of passivation in the dark and under prolonged white light illumination. Corresponding cathodic linear sweep voltammetry, open circuit decay and photopotential measurements were also carried out. Some novel results concerning the formation of α-PbO2 and non-stoichiometric PbOx under illumination are presented. Scanning electron micrographs of the electrode surface after passivation in the dark and under illumination are also reported.

The effect of prolonged white light illumination on the anodic passivation of lead in sulphuric acid

The anodic potentiostatic oxidation of lead electrodes in aqueous sulphuric acid at 0.4, 0.6 and 0.8 V vs. a Hg/Hg 2SO 4 external reference electrode was examined under conditions of passivation in the dark and under prolonged white light illumination. Corresponding cathodic linear sweep voltammetry, open circuit decay and photopotential measurements were also carried out. Some novel results concerning the formation of α-PbO 2 and non-stoichiometric PbO x under illumination are presented. Scanning electron micrographs of the electrode surface after passivation in the dark and under illumination are also reported.

Low‐Rate Cathodic Linear Sweep Voltammetry (LSV) Studies on Anodized Lead

Low‐rate (∼ 0.5 mV/sec) cathodic linear sweep voltammetry (LSV) experiments were conducted on preanodized antimonial and nonantimonial lead. The sweeps were supplemented by current‐time traces obtained during the short term (≤ 1 hr) anodic treatment above the reversible potential in electrolytes. Despite complications from additional substrate corrosion during the sweeps, semiquantitative observations were possible and the cathodic discharge could be resolved into components. A major finding was that antimony in the lead retards the formation of in the preliminary anodic treatment. Implications from the results with regard to the behavior of the Pb‐acid battery positive plate are briefly discussed.