EQCM Analysis Research Articles

Influence of suppressing additive malachite green on superconformal cobalt electrodeposition

• Adsorption-coordination mechanism was calculated by quantum chemistry to demonstrate the inhibition effect of MG. • Adsorption-transport mechanism was illustrated to explain the bottom-up growth of cobalt under the influence of MG. • The nucleation and growth of cobalt is 3D diffusion-controlled progressive nucleation process. A novel suppressor, malachite green, was used to achieve bottom-up growth of cobalt in this work. Electrostatic potential, HOMO/LUMO of malachite green was calculated to provide an insight into the interaction between malachite green and metal substrate, while charge distribution, AIM (atoms in molecules theory) analysis and IRI (interaction region indicator) analysis were coupled to analyze the interaction between malachite green and cobalt ions. Adsorption-coordination inhibition mechanism was illustrated to explain the inhibition effect of malachite green. Electrochemical analysis was applied to evaluate malachite green. Cyclic voltammetry was used to confirm the inhibition effect of malachite green, while EQCM analysis demonstrates that the current efficiency was lowered by MG. The nucleation and growth of cobalt is 3D diffusion-controlled progressive nucleation growth under the influence of hydrogen evolution reaction and the compact cobalt coatings could be obtained by surface analysis. The effective MG concentration gradient could be formed within blind vias according to current transient analysis so as to develop electroplating rate difference. The bottom-up growth of cobalt within blind vias was achieved by carrying out electroplating test and the adsorption-transport mechanism was proposed to explain the superconformal electrodeposition of cobalt under the influence of MG.

EQCM Analysis of the Process of Electrochemical Insertion in Regioregular Alkyl-Susbtituted Polyterthiophene during n-Doping

The material produced through the electrochemical polymerization of 3′4′-DDTT has been characterized with the EQCM during the process of n-doping. The supporting electrolyte (SE) was chosen considering mainly the two characteristics of hydrophobicity (to avoid the presence of water as potential contaminant) and chemical affinity with the alkyl and aromatic moieties present in poly-3′4′-DDTT. On these bases the salt (n-C4H9)4NClO4 was selected as SE since it contains the organic molecular cation (n-C4H9)4N+ that is expected to represent the charge compensating species in poly-3′4′-DDTT during n-doping. The feature of the reversibility of the electrical current profiles originated by the process of injection/extraction of electronic charge carriers in poly-3′4′-DDTT, is not encountered in the associated EQCM data. The interpretation of the EQCM data requires the consideration of phenomena of different nature. In the present work a thorough discussion of the factors influencing the EQCM response during polymer n-doping is provided taking into account the spontaneous adsorption of cations, the eventual reorientation of poly-3′4′-DDTT on the substrate and the consequences of the chains rearrangement on the electrical polarizability of poly-3′4′-DDTT during the cycles of electrochemical n-doping and undoping.

EQCM analysis of intercalation species into graphite positive electrodes for Al batteries

AlCl4− ions are considered the intercalated species, reversibly intercalated/deintercalated between graphite layers, when graphite is used as an active material for Al batteries; however, the reaction mechanism of intercalated species in Al batteries has not yet been fully understood. In order to understand the process, we quantitatively evaluated the charge/discharge reactions of graphite in an ionic liquid consisting of 1-ethyl-3-methylimidazolium chloride and AlCl3 by electrochemical quartz crystal microbalance and density functional theory calculations. The presence of AlCl4− and Al2Cl7− as the intercalated species in the graphite interlayer was confirmed at a ratio of 0.76:0.24. Additionally, the capacity was retained after the destruction of the graphite structure because of its pseudocapacitive behavior.

Recovery of indium based on the combined methods of ionic liquid extraction and electrodeposition

The diluent characteristics and the wide electrochemical window of the ionic liquid (IL), n-hexyl-trimethyl ammonium bis(trifluoromethyl-sulfonyl)amide; [N1116][TFSA], have been exploited for the extraction of In(III) from 1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methane sulfonamide (H[TFSA]) aqueous solution using 1.0 M tri-n-butylphosphate (TBP) in [N1116][TFSA], followed by direct electrodeposition as In metal from organic phase. The extraction mechanism of In(III) with TBP/[N1116][TFSA] has been investigated from the slope analysis. As a result, it was revealed that the extraction mechanism of In(III) in IL system was based on the following solvation extraction by TBP and the [N1116+] cation exchange extraction; [In(III)]aq + 3[TBP]IL + [N1116][TFSA]IL + 2[TFSA−]aq ↔ [In(TBP)33+(TFSA−)3]IL + [N1116+]aq. Moreover, the selective extraction of In(III) from the aqueous phase including Ni(II) and Zn(II) was performed in the range of pH = 1.5–4.0. The electrochemical behavior of extracted [In(TBP)33+] complex in [N1116][TFSA] on a platinum quartz crystal electrode was investigate by EQCM analysis. The reduction peak at −1.0 V was assigned at the [In(TBP)33+]/In(0) couple on the voltammogram. Potentiostatic electrodeposition of [In(TBP)33+] at −1.0 V allowed us to obtain the blackish electrodeposits, which were identified as most of In metal by EDX and XRD analyses.

EQCM Analysis of Redox Behavior of CuFe Prussian Blue Analog in Mg Battery Electrolytes

A wide variety of ions and molecules can be accommodated in the framework structure of Prussian blue (PB) and its analogs (PBAs). Mono- and polyvalent ions accommodated in the PB framework structure and PBAs can be extracted or re-inserted by redox reactions of transition metal ions composing the framework for charge compensation. In the present work, we report the detailed mechanism of the electrochemical inseration/extraction of Mg2 + ions and the effect of anions on the redox chemistry of a PBA composed of Cu and Fe ions by electrochemical quartz crystal microbalance and X-ray absorption spectroscopy. Furthermore, we evaluated the PBA as an active material using aqueous and organic electrolytes for Mg battery systems, and clarified that the redox potential of CuFe-PBA is approximately 3 V vs. Mg/Mg2 + in both aqueous and organic electrolytes.

Mechanism for the Formation of Black Cr-Co Electrodeposits from Cr3+ Solution Containing Oxalic Acid

One possible mechanism for the growth of Cr-Co electrodeposits from 1.0 M CrCl3·6H2O + 0.1 M CoCl2 + 0.5 M H2C2O4 at 25°C was proposed based on the results of careful EQCM, XPS, TEM, HRTEM, and EELS analysis. During the initial electrodeposition time, the Co2+, which is nobler than Cr3+, preferentially nucleates and grows perpendicular to the electrode surface, although arborescent patterns soon appear and further ramify with thinner, bent branches over time. This bulk encapsulating structure can easily trap the OH− ions formed by cathodic hydrogen evolution, thereby retarding the diffusion and further increasing the pH of the solution. This may accelerate the formation of Cr2O3 throughout most of the metallic-Co-free zone.

EQCM analysis of redox behavior of Prussian blue in a lithium battery electrolyte

Prussian blue (PB) and its analogues (PBAs) have been intensively studied and are now increasingly attractive for battery applications in particular because of their ability to accommodate a wide variety of ions including polyvalent cations. The redox reactions of PB and PBAs are believed to be very fast and reversible. However, it is not always true. In this paper, we clarify the detailed redox behavior of PB in an electrolyte for Li (ion) batteries using an electrochemical quartz crystal microbalance under an Ar atmosphere. We quantitatively report for the first time that the electrochemical adsorption/desorption of PF6− ions occurs in addition to the insertion/extraction of Li+ ions upon the redox reactions of PB. The adsorption of PF6− ions is followed by the extraction of Li+ ions during the oxidation of PB, and the adsorbed PF6− ions hinder the extraction of the Li+ ions. In contrast, the adsorbed PF6− ions do not affect Li+ ion insertion because the PF6− ions are desorbed before the insertion of Li+ ions during the reduction of PB. These results show that for practical applications the size of the framework structure should be selected by comparing the anion size in addition to the cation size.

EQCM and XPS analysis of 1,2,4-triazole and 3-amino-1,2,4-triazole as copper corrosion inhibitors in chloride solution

In this study, the influence of the amino functional group in the 1,2,4-triazole at position C3 (the 3-amino-1,2,4-triazole compound), on the surface layer formation and surface chemistry of these two Cu corrosion inhibitors is explored. Special attention is devoted to the orientation of these two molecules and the way they bond to the Cu surface. With the aim of obtaining electrochemical quartz crystal microbalance and X-ray photoelectron spectroscopy measurements, the article discusses why differences in the corrosion inhibition effectiveness of these two molecules exist. Moreover, the thicknesses of the inhibitor surface layers formed on the Cu are determined.

Stability-enhanced indium hexacyanoferrate electrodes: Morphological characterization, in situ EQCM analysis in nonaqueous electrolytes and application to a WO 3 electrochromic device

This paper presents a promising transparent counterelectrode system for a WO 3 electrochromic device (ECD) on the basis of a stability-enhanced indium hexacyanoferrate (InHCF) electrode and a NaClO 4/propylene carbonate (PC) electrolyte. Through SEM characterization it was found that clusters of granular InHCF nanoparticles (ca. 80–140 nm) were deposited on ITO substrates in HCl and KCl-stabilized plating solutions, and uniform micrometer thick films with high charge capacity could be obtained. From in situ electrochemical quartz crystal microbalance study, it was discovered that Na + would enter or move out from the InHCF film in the “desolvated” form during the redox process in a PC electrolyte. Besides, NaClO 4/PC resulted in higher electrochemical activity and reversibility than LiClO 4/PC. With these discoveries, a durable WO 3-InHCF ECD featuring blue-to-colorless electrochromism was fabricated successfully. The device remained 73.6 and 88.7% of its initial Δ T values at 600 and 800 nm after 40,000 rapid and successive coloring/bleaching cycles, respectively. Moreover, the cycling-induced loss of electrochromic performance almost completely restored after 1-month rest and kept unchanged for another month. Thus, the applicability of this nonaqueous InHCF counterelectrode system to ECDs was verified.

EQCM analysis of Bi oxidation mechanism on a Pt electrode

The electro-oxidation behaviours of bismuth (Bi) species adsorbed on a platinum (Pt) anode were investigated using an in situ electrochemical quartz crystal microbalance analysis in the measurement of cyclic voltammetry (CV) and electrochemical impedance spectroscopy under potentiostatic mode. In the CV of Bi modified Pt, there were four distinct features in the current–potential curves during an anodic scan: (i) the adsorption of water molecules in acidic media, (ii) the formation of Bi oxide, (iii) ionization of Bi oxide and (iv) partial desorption of Bi species. During a cathodic scan, the Bi modified Pt surface recovered to its original state via the reduction of Bi oxide and re-deposition of Bi ion. Surface mass data with electrical charge change and impedance measurements of Bi modified Pt supported the electrocatalytic oxidation of bismuth species as the responsible mechanism.

Electrochemical preparation and redox/ion exchange properties of polypyrrole in aqueous sodium hexafluoroaluminate

Electrodeposition and redox switching performance of polypyrrole in aqueous solution of sodium hexafluoroaluminate are described. An incorporation of NaAlF62− into the polymer phase is indicated by the EQCM analysis of electrodeposition. A SEM micrograph shows a characteristic morphology of the polymer layer. A mechanism of the redox process of polypyrrole is discussed based on CV and EQCM results involving the measurements performed as a function of a time scale of the redox cycle and a life time of the electrode. Structure determining interactions between polymer sites and counterions are indicated. Participations of ion-pair counterion, co-ion, salt, water, oxygen in the redox process of polypyrrole are discussed. A slow irreversible rearrangement in the structure/composition, inducing a change in the mechanism of the reversible redox process, is postulated to occur during the reduction process of the virgin anion-exchanging polypyrrole. Long time scale processes were observed to result in cation exchange properties accompanied by a substantial decrease in redox activity and/or CV currents of the polypyrrole electrode. The performance of the primary hexafluoroaluminate counterion electrode, prepared in aqueous solution of sodium hexafluoroaluminate, is compared to the secondary hexafluoroaluminate counterion electrode, prepared in a presence of the sodium chloride solution. In general, the CV and EQCM characteristics of the two system are similar due to pronounced contribution of the bathing electrolyte to the performance of the polymer electrode.

Electrochemical and chemical synthesis and characterization of sulfonated poly(3,4-ethylenedioxythiophene): A novel water-soluble and highly conductive conjugated oligomer

Electrochemical and chemical polymerization of a 3,4-ethylenedioxythiophene derivative bearing a sulfonate group (EDTS) is reported. The electrochemical polymer, poly(EDTS), which is very soluble in water, has been produced both from acidic water, resulting in the solution form, and from acetonitrile using additional perchloric acid in 1:1 ratio to the monomer, resulting in the production of polymer films. Both forms were characterized by cyclic voltammetry, UV-Vis spectroscopy, EQCM analysis, MALDI-TOF MS and conductivity measurements, and show high conductivity (0.5–10 S · cm−1) and high solubility in water (> 10%). Poly(EDTS) was also prepared by chemical polymerization with Fe(OTs)3 in water to yield once more a water-soluble and conductive (1–5 S · cm−1) polymer.

Low-Defect Neutral, Cationic, and Anionic Conducting Polymers from Electrochemical Polymerization of N-Substituted Bipyrroles. Synthesis, Characterization, and EQCM Analysis

Various 2,2‘-bipyrroles N-substituted with alkyl, alkylsulfonate, or alkylammonium moieties have been anodically coupled to polymers. The polymers were characterized by cyclic voltammetry, UV−vis and FTIR spectroscopies, EQCM, and in situ conductivity. Coupling of dipyrroles instead of pyrroles minimizes the introduction of overoxidative defects into the polymer chain (from FTIR spectroscopy). The polymer of N-alkylammonium-N-hexyldipyrrole is soluble in acetonitrile. EQCM analysis of the oxidative doping process of the polymers in acetonitrile has shown that the alkyl- and alkylammonium-substituted polymers increase their mass with doping, whereas the mass decreases in the case of alkylsulfonate-substituted polymers provided with tetralkylammonium counterions. Electrochemical muscles built from the most representative polymers show marked deflections that follow the EQCM mass/charge changes.

Dioxygen-decomposition of ferrocenium molecules in acetonitrile: The nature of the electrode-fouling films during ferrocene electrochemistry

Abstract Decomposition of ferrocenium by dioxygen in acetonitrile +0.1 M But4NClO4 is reported. The nature of the products has been investigated by CV, FTIR, GC-MS, EQCM and elemental analysis. The insoluble materials, responsible for the commonly encountered electrode fouling during ferrocene oxidation in incompletely degassed solutions, is a mixture of hydrous iron(III) oxide and the organic polymer poly(cyclopentane-1,3-dione-4,5-diyl). Soluble products are mainly constituted by Fe(III) perchlorate, 4-cyclopenten-1,3-dione, tricyclo[5.1.2.0(2,6)]deca-4,8-dien-3,10-dione and related oligomers.

Highly Ordered Poly(cyclopentabithiophenes) Functionalized with Crown-Ether Moieties for Lithium- and Sodium-Sensing Electrodes

Functionalized cyclopentadithiophenes 2 and 3 were synthesized and polymerized by anodic coupling, in acetonitrile solution, in the presence of 0.1 M tetraethylammonium perchlorate as supporting electrolyte. The former carries a 16-crown-5-ether ring coplanar to the bithiophene moiety, while a perpendicular 15-crown-5-ether ring is present in the latter. The cyclic voltammogram of poly-2 shows two redox processes at E° = −0.3 and +0.3 V, whereas that of poly-3 consists of a single response at E° = 0.0 V. The difference in electrochemical behavior is attributed to the occurrence of strong polaron π-dimerization in poly-2. The redox potential (E°) of this polymer moves toward more positive values passing from lithium to sodium salts as supporting electrolytes in acetonitrile solution. The redox cycle of poly-3 is instead completely insensitive to the change of the cationic species in solution. EQCM analysis shows that (i) both neutral polymers incorporate one alkaline ion per crown ring, (ii) the p-doping p...

Electrochemistry of Disulfide Compounds: I . Electrochemical Polymerization‐Depolymerization Process of 2,5‐Dimercapt‐1,3,4‐thiadiazole

The electrochemical polymerization‐depolymerization of an organodisulfide compound, 2,5‐dimercapt‐1,3,4‐thiadiazole (DMcT), was investigated under in situ conditions by quartz crystal microbalance (EQCM) and atomic force microscopy (AFM) measurements employed simultaneously with electrochemical voltammetry. The EQCM results, together with the cyclic voltammetric results, suggest that the polymerization and depolymerization processes of DMcT do not occur with the same coulombic efficiency. The number of electrons consumed during the polymerization process is greater than that for the depolymerization process, indicating that some other chemical process occurs at the same time. The EQCM analysis and AFM observations indicated that the oxidation of DMcT, especially at higher potentials, involves not only a straightforward polymerization process via S‐S bonds but also an overoxidation or degradation (decomposition) process of the poly(DMcT) deposited on the electrode surface. The AFM images of the deposited poly(DMcT) show smooth/uniform and isolated/island growth at low (0.8 V) and high (1.4 V) potentials, respectively. Substantial decomposition of poly(DMcT) was confirmed from both EQCM and AFM analysis when the polymer was formed at high potential (1.4 V). This behavior can be regarded as a serious drawback when the material is used as battery material.