Combined Electrochemical Quartz Crystal Microbalance Research Articles

Decoupling of the Impedance of Solid-Electrolyte Interface and Plated Lithium: Implications for Anode-Free Lithium Metal Battery Technology

The understanding of the impedance response during the cycling process of the “anode-free” lithium metal batteries is ambiguous in the literature. Herein, we report on a combined electrochemical quartz crystal microbalance and electrochemical impedance spectroscopy study to decouple the various contributions of the impedance response of an anode-free battery. This decoupling is achieved by a comparison of the evolution of electrochemical impedance spectroscopy spectra in two- and three-electrode cells during the Li plating–stripping processes. The observed high- and medium-frequency loops of the impedance spectra can be unambiguously assigned to the charge transfer in the solid-electrolyte interface and the plated lithium layers, respectively.

Gel polymer dominated ion charging mechanisms within graphene nanochannels

Revealing microscopic real-time ion transport behavior is critically-important for understanding the charging mechanisms of polymer electrolytes. Herein polymer dominated ion charging mechanism of LiCl/polyvinyl alcohol (PVA) gel polymer electrolytes within graphene nanochannels is observed by combined electrochemical quartz crystal microbalance (EQCM) and molecule dynamics (MD) simulations. This is substantially different with the conventional aqueous electrolytes, demonstrating the dominated role of PVA polymer (including polymer-ion and polymer-electrode interactions) in mediating the charging mechanisms. Specifically, in-situ EQCM measurement reveals that –OH polar groups of PVA exhibit more significant hindrance to cations than anions, yielding the charging mechanisms from Li+ adsorption/desorption (at 0 wt % PVA) to Li+/Cl− ion exchange dominated transport (at 40 wt % PVA). Furthermore, ionic flux is quantitatively characterized based on the non-equilibrium thermodynamics, and the charging resistance is revealed via combining constant potential method and equivalent electric circuits. More importantly, increasing PVA concentration remarkably affects the thermodynamic properties (e.g., dielectric property, angle distribution and number density), while almost identical capacitance is recognized because of higher dielectric constant of PVA molecules. By solving Poisson equation, this is further interpreted and invalidated by quantifying the contributions of ions, solvents and PVA molecules to the electric potentials.

Spectro-Electro-Gravimetry of Poly (o-toluidine)

Polyaniline and derivatives are one of ICPs most investigated [1-4]. Despite the considerable advances on the knowledge of the electrochemical reactions in this family of ICPs, it is still generally assumed that a “simple” transition from insulating form (leucoemeraldine or LE) to conductor form (emeraldine or E) by anion doping takes place with the formation of polaron centers [5]. Nekrasov et al and Hillman et al have proven that this transition is more complex than assumed or discussed in literature. On the one hand, Hillman et al have suggested a slow-moving solvent counter flux with a fast anion insertion together with a proton expulsion during this transition, at least, in HClO4 solution [6,7]. On the other hand, Nekrasov et al have proven that two different species are generated and coexist during this transition: (i) the isolated polarons or radical cations (P*) with a spectral response around 420 nm and the (ii) the conducting polarons which are coil structures due to the strong interaction of anions with the C-NH+-C group (PC) with a spectral response around 840 nm [8-10]. We present a more detailed electrochemical mechanism for the insulating to conductor transformation of POT films. During the relaxation, protons are expulsed when the isolated polarons (P*) detected at 420 nm are oxidized. Isolated polarons could be formed because of trapped anions when the film is reducing and shrinking (packing). Anions are inserted during the formation of conducting polarons (PC), which consist in coil structures due to the strong interaction of anions with the C-NH+-C group of polymer detected at 840 nm. [1] A. Syed, M. Dinesan, Polyaniline - a Novel Polymeric Material - Review, Talanta. 38 (1991) 815–837. doi:10.1016/0039-9140(91)80261-W.[2] T.H. Qazi, R. Rai, A.R. Boccaccini, Tissue engineering of electrically responsive tissues using polyaniline based polymers: A review, Biomaterials. 35 (2014) 9068–9086. doi:10.1016/j.biomaterials.2014.07.020.[3] R.Y. Suckeveriene, E. Zelikman, G. Mechrez, M. Narkis, Literature review: conducting carbon nanotube/polyaniline nanocomposites, Reviews in Chemical Engineering. 27 (2011) 15–21. doi:10.1515/REVCE.2011.004.[4] J. Lai, Y. Yi, P. Zhu, J. Shen, K. Wu, L. Zhang, J. Liu, Polyaniline-based glucose biosensor: A review, Journal of Electroanalytical Chemistry. 782 (2016) 138–153. doi:10.1016/j.jelechem.2016.10.033.[5] G. Ćirić-Marjanović, Recent advances in polyaniline research: Polymerization mechanisms, structural aspects, properties and applications, Synthetic Metals. 177 (2013) 1–47. doi:10.1016/j.synthmet.2013.06.004.[6] M.J. Henderson, A.R. Hillman, E. Vieil, Ion and Solvent Transfer Discrimination at a Poly(o-toluidine) Film Exposed to HClO4 by Combined Electrochemical Quartz Crystal Microbalance (EQCM) and Probe Beam Deflection (PBD), J. Phys. Chem. B. 103 (1999) 8899–8907. doi:10.1021/jp9910845.[7] M. J. Henderson, A. Robert Hillman, E. Vieil, A combined electrochemical quartz crystal microbalance (EQCM) and probe beam deflection (PBD) study of a poly(o-toluidine) modified electrode in perchloric acid solution, Journal of Electroanalytical Chemistry. 454 (1998) 1–8. doi:10.1016/S0022-0728(98)00245-9.[8] A.A. Nekrasov, V.F. Ivanov, A.V. Vannikov, Analysis of the structure of polyaniline absorption spectra based on spectroelectrochemical data, J. Electroanal. Chem. 482 (2000) 11–17. doi:10.1016/S0022-0728(00)00005-X.[9] A.A. Nekrasov, V.F. Ivanov, A.V. Vannikov, Effect of pH on the structure of absorption spectra of highly protonated polyaniline analyzed by the Alentsev-Fock method, Electrochimica Acta. 46 (2001) 4051–4056. doi:10.1016/S0013-4686(01)00693-4.[10] A.A. Nekrasov, V.E. Ivanov, O.L. Gribkova, A. Vannikov, Voltabsorptometric study of “structural memory” effects in polyaniline, Electrochimica Acta. 50 (2005) 1605–1613. doi:10.1016/j.electacta.2004.10.030. Part of this work was supported by MINECO-FEDER CTQ2015-71794-R.

Application of the combined electrochemical quartz crystal microbalance and probe beam deflection technique in deep eutectic solvents

The electrochemical quartz crystal microbalance (EQCM) and probe beam deflection (PBD) have been widely used to study interfacial processes in molecular solvent-based electrolytes. However, there has been limited use of the EQCM and none of PBD in room temperature ionic liquids, including deep eutectic solvents (DES). Here we explore the use of the combined EQCM/PBD technique to the study of Ag and Sn electrodeposition from a DES comprising a 1:2 mixture of choline chloride and ethylene glycol. While overcoming the effect of viscous loss in the acoustic wave (EQCM) part of the experiment is understood, the optical (PBD) technique fails to provide a meaningful response in slow scan rate voltammetric experiments; this contrasts sharply with the straightforward behaviour seen in aqueous media. Solution transport considerations reveal this to be a consequence of long surface-to-beam transit times in the viscous DES. The problem can be overcome by operating at scan rates 1-2 orders of magnitude slower, permitting application of this powerful technique to novel media of technological interest. The PBD responses reveal unanticipated chemical effects: multiple complexes in the Ag system and solubility limitations in the Sn system, neither of which is evident from the electrochemical or QCM responses.

Characterization of the SEI on a Carbon Film Electrode by Combined EQCM and Spectroscopic Ellipsometry

The electrochemical quartz crystal microbalance (EQCM) and cyclic voltammetry have been applied simultaneously to characterize electron-beam deposited carbon film electrodes in -containing mixed electrolytes of ethylene carbonate (EC) and dimethyl carbonate (DMC). The structure of the carbon electrode was found to be amorphous/disordered using Raman spectroscopy. Cyclic voltammetry in demonstrated features typical of Li intercalation/deintercalation into/from the disordered carbon electrode, and EQCM showed a corresponding mass increase/decrease. Combined EQCM and spectroscopic ellipsometry data were compared, and the solid electrolyte interphase density after the first cycle in was estimated to be 1.3 © 2003 The Electrochemical Society. All rights reserved.

Temporal resolution of ion and solvent transfers at nickel hydroxide films exposed to LiOH

A combined electrochemical quartz crystal microbalance (EQCM) and probe beam deflection (PBD) instrument was used to monitor mobile species transfers on short time scales following the application of a potential step to potentiostatically deposited α-nickel hydroxide films exposed to aqueous LiOH solution. Upon film oxidation, hydroxide ions enter the film and protons are deintercalated. However, the protons are not detected directly since, upon ejection from the film, they immediately combine with hydroxide ions from the solution to yield water. The relatively rigid film lattice (which allows gravimetric interpretation of the EQCM response) imposes volume constraints. As ions are driven into/out of the film in order to satisfy electroneutrality, this volume constraint causes solvent to be driven out of/into the film by internal pressure. Consequently, solvent transfer is forced into the same time scale as ion transfer and is no longer simply diffusionally controlled. Combining the EQCM/PBD-derived fluxes of individual mobile species with their molar volumes, one can estimate the implied changes in film volume driven by redox switching. These volume changes are relatively small and correspond to a monotonic expansion on film oxidation and a transient expansion then eventual contraction upon film re-reduction. These observations are in the opposite sense to those predicted on the basis of unit cell volumes for crystalline α-Ni(OH) 2 and γ-NiOOH, suggesting that the material studied is poorly represented by these idealised structures.

Ion and solvent transfer discrimination at a nickel hydroxide film exposed to LiOH by combined electrochemical quartz crystal microbalance (EQCM) and probe beam deflection (PBD) techniques

Abstract A combined electrochemical quartz crystal microbalance (EQCM) and probe beam deflection (PBD) instrument was used to monitor the mobile species transfers associated with the redox processes of thin ( Γ ≅100–150 nmol cm −2 ) α- and β-nickel hydroxide films exposed to aqueous LiOH solution. A comparison of the measured PBD signal with the predicted PBD profiles, calculated by temporal convolution analysis of the current and mass responses, enabled the contributions to redox switching of anion (OH − ) and solvent (H 2 O) transfers to be discriminated quantitatively. The responses from the combined instrument are reconciled in terms of H + deintercalation/intercalation within the nickel hydroxide structure as OH − ions enter/exit the film. Hydroxide ion movement is associated with a counterflux of water. Thin nickel hydroxide films show a gradual α→β phase transformation with continuous voltammetric cycling, especially when the films are exposed to high concentrations of electrolyte. α-Films are characterised by OH − transfers that dominate the H + and H 2 O movements; β-films are characterised by an increased participation of water and protons to the exchange dynamics.

Lead Underpotential Deposition on Polycrystalline Gold Electrode in Perchloric Acid Solution: A Combined Electrochemical Quartz Crystal Microbalance and Probe Beam Deflection Study

A quantitative combined electrochemical quartz crystal microbalance (EQCM) and probe beam deflection (PBD) analysis of Pb underpotential deposition in aqueous 0.1 mol dm−3 perchloric acid solution at polycrystalline gold was achieved by comparing the cyclic-voltammetric, -gravimetric, and -beam deflection responses. The refractive index responses (PBD) were commensurate with the large variation in index of refraction of with change in concentration (30.5 cm3 mol−1), demonstrating that the technique is remarkably sensitive to monitor the formation of submonolayers of In this work the current and mass variation signals were projected upon the beam deflection profile by using the mathematical tool of quantitative temporal convolution. We show that the overall process of occurs in three distinct stages. The first stage consists of water ejection from gold. In the second stage, metal underpotential deposition is accompanied by displacement followed, in the last step, by water formation. The coupled diffusion coefficient of transferring in solution was evaluated to be © 2001 The Electrochemical Society. All rights reserved.

Chronoamperometric resolution of ion and solvent transfers at a poly( o-toluidine) modified electrode by combined electrochemical quartz crystal microbalance (EQCM) and probe beam deflection (PBD)

Combined electrochemical quartz crystal microbalance (EQCM) and probe beam deflection (PBD) measurements on short time scales following the application of a potential step are presented. The procedure for evaluating the exchange of mobile species (ions and solvent) is illustrated by application of the combined technique to a poly( o-toluidine) (POT) film redox switching in aqueous HClO 4 solutions. A comparison of the predicted PBD profiles calculated from the current and mass responses to that of the measured PBD signal, by temporal convolution analysis, enabled the contributions of anion (ClO 4 −) and solvent (H 2O) transfer at the first redox step to be discriminated quantitatively. The results are consistent with a mechanism where anion exchange involves a counter flux of solvent, and suggest that a film volume constraint is applicable on the time scale of the experiment. During oxidation and reduction, the EQCM indicates a non-equilibrium movement of anions, confirmed by convolution analysis of the associated current and deflection signals.

PbTe electrodeposition studied by combined electrochemical quartz crystal microbalance and cyclic voltammetry

Electrodeposition of PbTe thin films from alkaline solutions, and the electrochemical behavior of the related precursors TeO32− and PbEDTA2−, were studied for the first time by means of an electrochemical quartz crystal microbalance (EQCM) combined with cyclic voltammetry. PbTe was found to form by an induced codeposition mechanism via six electron reduction. The reduction mechanism of Te was complicated and sensitive to the substrate surface. On the other hand, the reduction of the PbEDTA2− complex to Pb0 was a simple two electron reaction.

Electrochemical quartz crystal microbalance and cyclic voltammetry studies on PbSe electrodeposition mechanisms

Electrochemical reactions involved in the electrodeposition of PbSe and the electrochemical behaviour of the related precursors, HSeO3− and Pb(EDTA)2−, have been studied for the first time by combined electrochemical quartz crystal microbalance and cyclic voltammetry measurements. Formation of PbSe was found to occur by an induced codeposition mechanism via a six-electron reduction reaction. HSeO3− is reduced by a four-electron reaction but the electrode becomes passivated. The reduction and oxidation of Pb(EDTA)2− occur via two-electron mechanisms, on the other hand, during the oxidation adsorption reactions are also observed.

Ion and Solvent Transfer Discrimination at a Poly(o-toluidine) Film Exposed to HClO4 by Combined Electrochemical Quartz Crystal Microbalance (EQCM) and Probe Beam Deflection (PBD)

A combined electrochemical quartz crystal microbalance (EQCM) and probe beam deflection (PBD) instrument was used to monitor the mobile species transfers at the first and second redox steps of thin (Γ ≅ 5 × 10-8 mol cm-2) poly(o-toluidine) films exposed to either 0.01, 0.1, or 1.0 mol dm-3 HClO4 aqueous electrolyte. A comparison of the predicted PBD profiles calculated from the current and mass responses to that of the measured PBD signal, by temporal convolution anaysis, enabled the contributions of cation (H+), anion (ClO4-), and solvent (H2O) transfer at the first redox step to be discriminated quantitatively. A further separation of the slow moving solvent counter flux from fast ion exchange was possible by shortening the experimental time scale.

Combined electrochemical quartz crystal microbalance (EQCM) and probe beam deflection (PBD): validation of the technique by a study of silver ion mass transport

Abstract A quantitative combined electrochemical quartz crystal microbalance (EQCM) and probe beam deflection (PBD) analysis of the Ag+/Ago deposition/dissolution redox process in aqueous perchloric acid solution was achieved by comparing the cyclic -voltammetric, -gravimetric and -beam deflection responses. The recorded current and mass variation signals were superimposed upon the beam deflection profile by using the mathematical tool of quantitative convolution. The good correlation between the coulometric, gravimetric and optical signals, displayed in either differential or integral form, highlights the complementary nature of the responses from the combined instrument and demonstrates how current, mass and beam deflection represent a single electrochemical process.

A combined electrochemical quartz crystal microbalance (EQCM) and probe beam deflection (PBD) study of a poly(o-toluidine) modified electrode in perchloric acid solution

A combined electrochemical quartz crystal microbalance (EQCM) and probe beam deflection (PBD) instrument was used to monitor the effects of film history and redox state of an unhydrated poly(o-toluidine) modified electrode immersed in aqueous perchloric acid (pH=0) solution. The degree of film hydration affected the relative contributions of protons and anions exchanged during the first redox process and the potential of the first anodic voltammetric peak. A distinct proton contribution to the ion exchange during the first redox process was detected during the second and subsequent cycles. Electroneutrality during the second charge transfer step was maintained predominantly by proton expulsion. The determination of the diffusion coefficient of the exchanged species in the first redox process by the time dependence of laser beam deflection delay and by temporal convolution of the current signal are compared. The concomitant changes in the gravimetric and optical signals during film hydration demonstrate the participation of both proton and solvent during redox cycling of poly(o-toluidine).