Combination Of Cyclic Voltammetry Research Articles

Semiconductor Properties of Electrodeposited Manganese Dioxide for Electrochemical Capacitors: Mott-Schottky Analysis

Herein the semiconducting nature of electrodeposited manganese dioxide (γ-MnO2) is examined for its effects on pseudo-capacitive electrode behaviour in neutral electrolytes. Electrochemical analysis of the manganese dioxide electrode is achieved using a combination of cyclic voltammetry (CV), step potential electrochemical spectroscopy (SPECS) and electrochemical impedance spectroscopy (EIS), in particular the combination of SPECS and EIS in a single experiment, enabling the determination of electronic properties across the full potential window. After establishing stable cycling with CV, electrode performance is examined using SPECS. EIS data, recorded under quasi-equilibrium conditions at the end of each potential step rest period, is then analyzed using the Mott-Schottky equation, leading to the identification of both n-type and p-type behaviour for the manganese dioxide electrode. Flat band potentials are determined (Vfb,n = −0.34 V vs SCE and Vfb,p = 0.98 V vs SCE), and conclusions about the electrochemically active surface area being more closed related to the geometric surface area were reached.

Effect of Cosurfactant in the Electrochemical Response of Reverse Microemulsions Formed by the AOT+Pentanol/Isooctane/Solution of [Fe(CN)6]3− System: A Cyclic Voltammetry and Electrochemical Impedance Spectroscopy Study

Cyclic voltammetry (CV) is an electrochemical technique that has been used to characterize reverse microemulsions (RMs). By following the oxidation-reduction of an electroactive probe (EP) previously dissolved in the RM water droplets, the diffusion coefficient of such droplets can be obtained by relating the measured current and the concentration of the EP. This approach assumes that the current is due solely to the oxidation-reduction of the EP. Nevertheless, adsorption and other non-faradaic processes that are commonly observed in complex systems like RMs, especially in those that contain cosurfactants, can also contribute to the current. In this work, electrochemical impedance spectroscopy (EIS) is used to study these processes in RMs formed by AOT/isooctane/water, with pentanol as cosurfactant and [Fe(CN)6]3− as EP. The results indicate that pentanol is distributed in the bulk of the RM, which increases the conductivity of the whole system; and also adsorbed at the electrode, which decreases the charge transfer resistance. The combination of both effects explains the increase in the current observed when the amount of cosurfactant increases. As conclusion, using CV in combination with EIS measurement is recommended to characterize RMs and reaching a more complete understanding on the electrochemical behavior of the system.

Influence of Ligand Denticity and Flexibility on the Molecular Copper Mediated Oxygen Reduction Reaction.

To date, the copper complex with the tris(2-pyridylmethyl)amine (tmpa) ligand (Cu-tmpa) catalyzes the ORR with the highest reported turnover frequency (TOF) for any molecular copper catalyst. To gain insight into the importance of the tetradentate nature and high flexibility of the tmpa ligand for efficient four-electron ORR catalysis, the redox and electrocatalytic ORR behavior of the copper complexes of 2,2′:6′,2″-terpyridine (terpy) and bis(2-pyridylmethyl)amine (bmpa) (Cu-terpy and Cu-bmpa, respectively) were investigated in the present study. With a combination of cyclic voltammetry and rotating ring disk electrode measurements, we demonstrate that the presence of the terpy and bmpa ligands results in a decrease in catalytic ORR activity and an increase in Faradaic efficiency for H2O2 production. The lower catalytic activity is shown to be the result of a stabilization of the CuI state of the complex compared to the earlier reported Cu-tmpa catalyst. This stabilization is most likely caused by the lower electron donating character of the tridentate terpy and bmpa ligands compared to the tetradentate tmpa ligand. The Laviron plots of the redox behavior of Cu-terpy and Cu-bmpa indicated that the formation of the ORR active catalyst involves relatively slow electron transfer kinetics which is caused by the inability of Cu-terpy and Cu-bmpa to form the preferred tetrahedral coordination geometry for a CuI complex easily. Our study illustrates that both the tetradentate nature of the tmpa ligand and the ability of Cu-tmpa to form the preferred tetrahedral coordination geometry for a CuI complex are of utmost importance for ORR catalysis with very high catalytic rates.

Electrochemical Behavior of CsI in LiCl Molten Salt

The electrochemical behavior of CsI in LiCl molten salt was investigated to identify its impact on the electrolytic oxide reduction of oxide-phase spent nuclear fuels by combined electrolysis and cyclic voltammetry experiments of LiCl-CsI in comparison with LiCl, LiCl-CsCl, and LiCl-LiI. It was found that Cs+ ions were hardly involved in the cathode reaction, and reduction of Li+ ions occurred dominantly in the cathode. In contrast, incorporation of I− ions induced low-potential anode reaction compared with the I− ion-free cases. Such additional electrochemical reaction resulted in the generation of I2 and/or ICl gases, which would increase a process burden for treating 129I with exceptionally long lifetime. In this respect, separating CsI from spent nuclear fuel before the electrolytic oxide reduction is recommended for the purpose of efficient waste management.

Observation of Substituent Effects in the Electrochemical Adsorption and Hydrogenation of Alkynes on Pt{hkl} Using SHINERS.

By combining cyclic voltammetry (CV) and shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS), the adsorption behavior of two alkynes, propargyl alcohol (PA) and 2-methyl-3-butyn-2-ol (MeByOH), undergoing hydrogenation on Pt basal plane single-crystal electrodes is investigated. It is found that PA and MeByOH give rise to strong surface sensitivities in relation to both hydrogenation activity and molecular fragmentation into adsorbed species such as CO. For PA, irreversible adsorption is strongly favored for Pt{100} and Pt{110} but is weak in the case of Pt{111}. It is suggested that the presence of the primary alcohol substituent is key to this behavior, with the order of surface reactivity being Pt{100} > Pt{110} > Pt{111}. In contrast, for MeByOH, strong irreversible adsorption is observed on all three basal plane Pt surfaces and we propose that this reflects the enhanced activity of the alkyne moiety arising from the inductive effect of the two methyl groups, coupled with the decreased activity of the tertiary alcohol substituent toward fragmentation. Pt{111} also exhibits singular behavior in relation to MeByOH hydrogenation in that a sharp Raman band at 1590 cm–1 is observed corresponding to the formation of a di-σ/π-bonded surface complex as the alkyne adsorbs. This band frequency is some 20 cm–1 higher than the analogous broadband observed for PA and MeByOH adsorbed on all other basal plane Pt surfaces and may be viewed as a fingerprint of Pt{111} terraces being present at a catalyst surface undergoing hydrogenation. Insights into the hydrogenation activity of different Pt{hkl} surfaces are obtained using quantitative comparisons between Raman bands at hydrogenation potentials and at 0.4 V vs Pd/H, the beginning of the double-layer potential region, and it is asserted (with support from CV) that Pt{110} is the most active plane for hydrogenation due to the presence of surface defects generated via the lifting of the (1 × 2) to (1 × 1) clean surface reconstruction following flame annealing and hydrogen cooling. Our findings are also consistent with the hypothesis that Pt{111} planes are most likely to provide semihydrogenation selectivity of alkynes to alkenes, as reported previously.

Diazonium based surface functionalization of graphite by electrochemical grafting

In this respect, a combination of cyclic voltammetry (CV), Raman spectroscopy, and Atomic Force Microscopy (AFM) is employed to characterize the structural, electrochemical and electronic properties of diazonium thin layers covalently functionalized highly oriented pyrolytic graphite (HOPG) surface. As a consequence, a grafted layer thin film of 4-nitro-benzene-diazonium tetrafluoroborate (4-NBD) is formed on HOPG surface with an average thickness of about 3.5 ± 0.2 nm. A D-band peak appearrance at the wave length of 1336 cm-1 on the Raman spectrum indicates an enhancing of defects caused by covalent C-C bonds. A tentative model illustrating the formation of 4-NBD grafted multilayer governed by the dendritic mechanism is also proposed. This finding opens a new approach to control the degree of functionalization of graphitic surfaces and other 2D materials.

Design bifunctional vanadium carbide embedded in mesoporous carbon electrode for supercapacitor and dye-sensitized solar cell

Vanadium carbide embedded in mesoporous carbon (VC–MC) is prepared using an in-situ synthesis method as hybrid electrode for supercapacitor. The electrochemical performance of the VC and VC–MC electrodes are analyzed and compared through a combination of cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy measurements in 1 M H2SO4 aqueous electrolyte. The introduced mesoporous structure of the hybrid electrode provides optimized conducting pathways for electrons and protons, thus improving the capacitive performance of VC–MC electrode compared to pristine VC electrode. The synthesized VC–MC electrode achieves a specific capacitance up to 191.2 F g−1, which is significantly higher than the pristine VC electrode (95.6 F g−1). Moreover, the VC–MC hybrid electrode exhibits an excellent cycle performance with 89.5% capacitance retention after 10,000 charge–discharge cycles, considerably higher than the pristine VC electrode. Apparently, the VC–MC hybrid electrode which shows desirable capacitive performance, excellent stability and enhanced electrochemical properties can be attributable to the combination of the advantages possessed by MC and VC. Moreover, VC–MC was applied as counter electrode in flexible dye-sensitized solar cell which generate power conversion efficiencies of 6.50%, much higher than those of the devices using VC and MC counter electrodes (4.14% and 5.28%).

Insights on the electrodeposition mechanism of tungsten oxide into conducting polymers: Potentiostatic vs. potentiodynamic deposition

In this work we have investigated the electrochemical deposition of tungsten oxide into different conducting polymer films from the metastable acidic solution of isopolytungstate. Two different in the nature conducting polymer (CP) materials, namely, poly-3,4-ethylenedioxythiophene (PEDOT) and poly-3,4-ethylenedioxypyrrole (PEDOP) were used as electrode substrates for electrodeposition. Electrodeposition of tungsten oxide into freshly prepared conducting polymer films was performed by two electrochemical methods: potentiostatic and potentiodynamic. The electrochemical behavior of CP/WO3 composites, obtained with variation of synthesis conditions, was investigated by cyclic voltammetry in 0.5 M sulfuric acid. The comparison of electrochemical properties of composites allows to conclude on the mechanism of WO3 deposition. It was shown that precipitates of WO3 in CPs, electrodeposited by potentiodynamic method, display very symmetrical and sharp peaks of the redox transformation of WO3, which are rarely reported for tungsten oxides.The effect of electrochemical deposition method on the growth of WO3 precipitates on conducting polymer film electrodes and the electrochemical properties of composites was also investigated by combined cyclic voltammetry and electrochemical quartz crystal microbalance (EQCM). The role of polyoxotungstate anion species trapping in CPs during p-doping process and facile formation of tungsten oxide nanostructures in CPs matrix is considered. A mechanism for the electrodeposition of tungsten oxide into PEDOT and PEDOP polymers was proposed.

(Invited) Investigations of Interaction and Molecular Structure of Additives on the Copper Electrodeposited Layer By Combination of Cyclic Voltammetry with Time-of-Flight Secondary-Ion Mass Spectrometry (TOF-SIMS)

Appropriate additives, such as polyethylene glycol, play the essential role of metal deposition suppressors and are required to control the fabrication process of copper electrodepositionon micro and nanoscale devices. Moreover, brighteners, accelerators and levellers are involved in adjusting of functional properties of the electroplating bath influencing roughness and waviness of deposited copper layer. Our recent studies [1] show that TOF-SIMS measurements under static regime can be conducted successfully for the identification of additives such as PEG, SPS, and Cl, accumulated on the copper electrodeposited layer.Especially, evaluation of molecular structure of the large molecules such as polyethylene glycol is very challenging and out of range for techniques such as SERS, widely applied for in situ studies under copper electrodeposition regime. On the other hand, traditional mass spectroscopy such as electrospray mass spectrometry are oriented on evaluation of composition of electroplating bath. Recently, we have developed a new approach for evaluation of additives on the copper layer by combination of cyclic voltammetry (CV) with TOF-SIMS. To determine the molecular structure of polyethylene glycol and its interaction with chloride and acceleratorson the copper electrodeposited layer CV experiment was conductedwhile a nitinol wire as a working electrode was withdrawn at constant speed from a copper electroplating bath. In that way applied potential during CV corresponds to position of the wire withdrawn from the electroplating bath. This approach allows to evaluate of distribution of chemical species in a function of the applied potential by ex situ TOF-SIMS measurements. Moreover,the thickness of the copper layer was controlled by laser scan micrometer. In the presence of brightener and leveler, the roughness was evaluated by atomic force microscopy in a function of length of wire. In that fashion, CV experiment combined with a molecular analysis, thickness and roughness of copper layer measurements bring complementary knowledge to comprehensively understand the processes occurring on the copper surface. This will have an application for the real-world samples in a wide range of thickness copper layer, applied potential and concentration of additives and copper sulfate.[1] R. Mroczka, R. Łopucki, G. Żukociński, Molecular analysis of additives and impurities accumulated on copper electrodeposited layer by time-of-flight secondary ion mass spectrometry, Applied Surface Science 463 (2019) 412–426

Electrochemical Reduction of Carbon Dioxide to Carbon Monoxide Using CVD N-Doped Graphene on Copper Foam As Carbo-/Electro-Catalyst

Nowadays, the increasing concentration of CO2 emission in our atmosphere is a serious environmental issue. According to an issue for preserving Earth’s Climate in the 13th UN Sustainable Development Goal, technologies that reduce both the carbon emissions of existing processes and those that efficiently utilize CO2 as feedstock for chemicals and fuels are necessarily required. Electrochemical reduction of CO2 (CO2R) is a promising method for converting this greenhouse gas into value-added products, utilizing renewable energy. A limitation is that CO2 is inert molecule () that requires considerable energy for chemical activation. In addition, the CO2R includes multiple steps of electron and proton transfer on catalyst surface. In general, the reduction potentials and product distribution for CO2R depend on experimental conditions, electrolytic solutions, and electrode materials. Herein, we used CVD nitrogen‐doped graphene on copper foam as carbo-/electro-catalyst (N-GP/Cu). To understand the selectivity of the as-prepared catalyst, we observe the electrochemical reduction product from CO2R using a combination of cyclic voltammetry (cv) and on-line mass spectrometry (DEMS). The presence of nitrogen heteroatom on the graphene sheet reduces the onset potential at ca. 0.5 V (vs. SCE) in 0.1M KHCO3 under CO2 gas. The N-GP/Cu can mainly convert CO2 into CO. We hope that this study may provide a guideline to develop the improved CO2 conversion catalyst.

Electrochemical Reduction of FAD for NSMOA‐Catalyzed Epoxidation Reactions

Styrene monooxygenase (SMO) is a two‐component flavoprotein composed of an NADH‐dependent flavin‐reductase (SMOB) and FAD‐dependent epoxidase (NSMOA). The SMO‐catalyzed enantioselective epoxidation of styrene has potential applications in green‐chemical aqueous phase synthesis and environmental remediation. In the present work, we investigate the possibility of eliminating the NADH‐dependence of this two‐component biocatalyst by developing an electrochemical system that can be substituted for SMOB as the source of reduced FAD as the rate‐limiting step in the styrene epoxidation reaction.In this work, a miniature spectroelectrochemical cell was constructed and interfaced with a potentiostat that enabled the study of electrode‐mediated flavin‐reduction reactions by cyclic voltammetry and diode array‐based UV‐vis spectroscopy under anaerobic and aerobic conditions. Different results were obtained depending on the composition of the working electrode in terms of the kinetics of FAD desorption from the electrode surface and the applied electrical potential required to achieve FAD reduction. Glassy carbon and graphene‐based working electrodes are observed to readily establish and remain in electrical communication with FAD, but the kinetics of FAD reduction in bulk solution is limited by the slow kinetics of FAD desorption from the surface of these working electrodes. Under aerobic conditions, oxygen diffuses within and reacts with reduced FAD adsorbed to the electrode surface in a reaction which is rapid compared with the kinetics of the desorption of reduced FAD. The implementation of more hydrophilic working electrodes prepared as composites of graphene and polyethylene glycol and the inclusion of electron carriers with oxidation reduction‐potentials in the range of FAD significantly improves the rate FAD desorption and reduction in bulk solution where the rapid kinetics of association of reduced FAD to the epoxidase (NSMOA) can efficiently out compete undesirable side reactions of reduced FAD with dissolved oxygen. In this work, we address the central challenges associated with the electrochemical reduction preparation and transmission of reduced FAD to styrene monooxygenase and report how this can be achieved efficiently by using a combination of cyclic voltammetry, electron mediators and an electrode material with rapid FAD desorption characteristics.Support or Funding InformationThis research is founded by NIH MBRS‐RISE (R25‐GM059298).Cyclic voltammetry of FAD at the surface of a glassy carbon electrode and saturation plot of the flavin interaction at the electrode surface.Figure 1Absorbance spectra recording the reduction of FAD (Left) and consumption of styrene (right) by UV‐Vis spectroscopy.Figure 2

Studying the effects of bismuth on the electrochemical properties of lead dioxide layers by using the in situ EQCM technique

The charge-discharge characteristics and the aging mechanism of PbO2 layers doped with bismuth in contact with sulfuric acid solutions were studied by using combined cyclic voltammetry and electrochemical quartz crystal microbalance (EQCM) techniques. For this purpose, thick lead dioxide layers (non-doped and doped with Bi) were electrodeposited on gold substrate from aqueous solutions of Pb(NO3)2 dissolved in nitric acid and they were investigated in sulfuric acid media. Based on the electrochemical and the mass change responses, it is concluded that during the electrodeposition, bismuth influences the structure of the PbO2 formed. Bi(III) also inhibits the oxidation of lead sulfate and affects the reduction kinetics of lead dioxide. During successive cyclization (aging), the presence of bismuth accelerates the hydration of PbO2.

The properties of the polyethylene glycol complex PEG(Na+)(Cu+) on the copper electrodeposited layer by Time-of-Flight Secondary-Ion Mass Spectrometry. The new insights

The properties of polyethylene glycol PEG(Na+)(Cu+) complex on the copper electrodeposition layer was studied by Time-of-Flight Secondary-Ion Mass Spectrometry (TOF-SIMS). The most stable PEG(Na+) fragment, C11H22O6Na+, consists of the central sodium ion surrounded by six ethereal oxygens atoms completed with a pseudo-crown ring. The mechanism of fragmentation pathways leading to the characteristic fragments for complexes PEG(Na+) and smaller fragments PEG(Cu+) was extensively discussed. The adsorption of PEG onto copper is stabilized by counterion effect of sodium ion with the chloride adlayer and hydrophobic interaction. Hydrophobic groups can be oriented towards the chloride adlayer, whilst ethereal oxygen with central sodium ion towards the electrolyte. Consecutively, additional bonds between ethereal oxygen of PEG and copper ions Cu+ (in the CuCl form), identified as a fragments C4H8O2Cu+, stabilize and increase adsorption of PEG molecules. The substitution of HCl as a source of Cl− onto NaCl at adjusted Cl− concentration, diminishes the suppressing abilities of PEG. Under an optimal Na+/Cl− ratio adsorption of PEG also occurs under an open circuit potential. The mechanism of the interaction between complex PEG(Na+)(Cu+) and the chloride adlayer and its importance for a suppressing abilities was provided. Adsorption of PEG(Na+) is strongly dependent on the applied electrode potential. It was also demonstrated that nine charged sodium sites are separated by linking chains, consisting of approximately 12 monomer CH2CH2O units. Our results show that the contamination of copper sulfate by sodium ions plays an important role as a source of sodium ion in forming pseudocrown ethers by polyethylene glycol. Due to this reason, the optimization protocols for suppressing abilities of PEG should take into account molar ratio Na+/Cl− as well as their concentrations. The study proves that a combination of cyclic voltammetry (CV) with TOF-SIMS under the static regime, where substrate wire is withdrawn from a bath in a controlled manner under electrodeposition condition is an extremely powerful tool for the evaluation of changes in chemistry species on the copper surface under real electrodeposition condition.

Electrochemically Induced Changes in TiO2 and Carbon Films Studied with QCM-D.

Semi-solid fluid electrode-based battery (SSFB) and supercapacitor technologies are seen as very promising candidates for grid energy storage. However, unlike for traditional batteries, their performance can quickly get compromised by the formation of a poorly conducting solid–electrolyte interphase (SEI) on the particle surfaces. In this work we examine SEI film formation in relation to typical electrochemical conditions by combining cyclic voltammetry (CV) with quartz crystal microbalance dissipation monitoring (QCM-D). Sputtered layers of typical SSFB materials like titanium dioxide (TiO2) and carbon, immersed in alkyl carbonate solvents, are cycled to potentials of relevance to both traditional and flow systems. Mass changes due to lithium intercalation and SEI formation are distinguished by measuring the electrochemical current simultaneously with the damped mechanical oscillation. Both the TiO2 and amorphous carbon layers show a significant irreversible mass increase on continued exposure to (even mildly) reducing electrochemical conditions. Studying the small changes within individual charge–discharge cycles, TiO2 shows mass oscillations, indicating a partial reversibility due to lithium intercalation (not found for carbon). Viscoelastic signatures in the megahertz frequency regime confirm the formation and growth of a soft layer, again with oscillations for TiO2 but not for carbon. All these observations are consistent with irreversible SEI formation for both materials and reversible Li intercalation for TiO2. Our results highlight the need for careful choices of the materials chemistry and a sensitive electrochemical screening for fluid electrode systems.

Self-assembly of porphyrin molecules on a Cu(111) electrode: Influence of different anions and electrode potential

In this contribution, we provide a view on the role of halide interlayers in the self-assembly of layers of organic molecules at metal-electrolyte interfaces with molecular resolution. In particular, the ordering of tetra(4-trimethylammoniophenyl) porphyrin molecules in cationic form, abbreviated as [H2TTMAPP]4+, has been studied on a Cu(111) electrode surface in aqueous solution containing chloride-, bromide- or iodide-anions using a combination of cyclic voltammetry (CV) and in-situ electrochemical scanning tunneling microscopy (EC-STM). On the one hand the obtained results unveil that the degree of ordering of the self-assembled layer of [H2TTMAPP]4+ cations on the Cu(111) surface changes significantly when changing the halide anion in the working electrolyte, and, thereby, the buffer layer between the Cu(111) surface and the adsorbed [H2TTMAPP]4+ molecular cations. Under the same experimental conditions a fully ordered layer is observed on the chloride precovered Cu(111) surface, but less ordering and even incomplete monolayer formation are found on the bromide and iodide terminated Cu(111) surface, respectively; the degree of order decreases with decreasing electronegativity of the underlying halide. On the other hand potential driven reduction of the organic species lowers the charge density of the organic cations themselves causing a desorption of the reduced molecules at even lower potentials from any of the three differently halide modified electrode surfaces. Both observations underline the importance of electrostatic interactions in the adsorption and structure formation of the porphyrin molecules on the halide modified surfaces.

Electrochemical formation of silver nanoparticles and their applications in the reduction and detection of nitrates at neutral pH

A glassy carbon electrode modified with silver nanoparticles was employed as a nitrate sensor to give a calibration curve with a sensitivity of 2.6 μA μM−1 cm−2 and a LOD of 4.1 μM NO3− at a neutral pH. The calibration curve was generated using rotating disc voltammetry coupled with constant potential amperometry, giving efficient diffusion of the nitrate to the surface. Reasonably good selectivity for nitrate was observed in the presence of nitrite, chloride and phosphate anions. The nitrate diffusion coefficient was estimated as 1.41 × 10−5 to 1.73 × 10−5 cm2 s−1 using a combination of cyclic voltammetry and rotating disc voltammetry, while the rate constant for the nitrate reduction reaction was estimated as 0.11 cm s−1. Some deviations from the Randles–Sevick and Levich equations were seen at higher scan rates, consistent with the slow kinetics and nitrate adsorption. While stable silver nanoparticles were electrochemically formed in the solution phase and incorporated within a hydrogel matrix, the best approach in forming the nitrate sensor was the direct electrodeposition of silver nanoparticles at glassy carbon at − 0.50 V versus Ag|Ag+ following a 60-min seeding period at the open-circuit potential.

Investigation of the electrochemical behaviour of lead dioxide in aqueous sulfuric acid solutions by using the in situ EQCM technique

The charge-discharge characteristics and the aging mechanism of PbO2 layers in contact with sulfuric acid solutions of different concentrations (1.5–5.0 M) were studied by using combined cyclic voltammetry and electrochemical quartz crystal microbalance (EQCM) techniques. For this purpose, thick lead dioxide layers were electrodeposited on gold substrate from aqueous solutions of Pb(NO3)2 dissolved in nitric acid. Based on the electrochemical and the mass change responses, it was found that in more concentrated solutions of H2SO4, the main reduction reaction was the transformation of lead dioxide to lead sulfate. However, in less concentrated sulfuric acid media, the transformation of lead dioxide to lead(II) ion became the main reaction. These Pb2+ ions transformed into lead sulfate crystals later by a chemical reaction. Because the electrochemical oxidation of lead sulfate is less favourable in sulfuric acid medium of higher concentrations, thus, PbO2 layers cannot be tested by continuous cyclization, which is necessary to study their aging parameters. Therefore, a delay step before each cyclic voltammogram was applied while the non-conductive lead sulfate dissolves or alternatively, by applying a pre-oxidation step prior to each cyclic voltammetry experiment to produce electrochemically significant amount of lead dioxide which can be reduced during the following negative potential sweep.

Understanding reaction mechanisms using dynamic electrochemical impedance spectroscopy: Methanol oxidation on Pt

Data from a combined cyclic voltammetry and dynamic electrochemical impedance spectroscopy (dEIS) study of the methanol oxidation reaction (MOR) at high temperatures was revisited using a new method for mechanistic modeling. Through iterative optimization of kinetic parameters, a total of five reaction mechanisms of the indirect pathway of the MOR were modeled. The calculated dEIS spectra from the kinetic parameters were used to verify the reaction mechanisms and best fits were found where i) water adsorption is reversible and hinders the MOR at lower potentials (< 0.50 V vs RHE), and ii) the surface reaction between adsorbed CO and OH is chemical.

Electrochemical detection of food-spoiling bacteria using interdigitated platinum microelectrodes

The fast and non-destructive detection of bacterial attachment on food contact surfaces is important for the prevention of the unwanted formation of biofilms. Biofilms constitute a protected growth mode that allows bacteria to survive even in hostile environments. Therefore, the fast detection of bacterial attachment may be an effective strategy for biofilm control. In this study cyclic voltammetry (CV) was used to detect Bacillus subtilis ssp. subtilis, Paenibacillus polymyxa, Pseudomonas fragi attachment on interdigitated microelectrodes. The differences in current between the uncolonized sterile microelectrodes and the microelectrodes after bacterial attachment were determined. In addition, the surface coverage of microelectrodes was visualized using microscopy techniques. The results showed that the cyclic voltammetry in combination with interdigitated platinum microelectrodes can be used to detect bacterial biofilms.

Effect of Chemical Structure on the Electrochemical Cleavage of Alkoxyamines

A test set of 14 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-based alkoxyamines was studied via a combination of cyclic voltammetry and accurate quantum chemistry to assess the effect of substitue...