Thin-layer Electrode Research Articles

Electrode coatings for high temperature hydrogen electrolysis

A discussion of fabrication techniques and performance testing of solid oxide components for use in hydrogen steam electrolysis is presented. Novel plasma spray techniques are utilized to deposit the thin ceramic oxide electrode, electrolyte, and interconnect layers on a planar intermetallic bipolar plate. Optimal porosity is achieved within the electrode microstructure through mixed feed techniques that are a combination of dry powder feed and liquid solution injection. The perovskite anode coatings formed from liquid precursor feedstock require post-deposition annealing in an oxygen-rich atmosphere to form the desired perovskite structures. Electrical conductivity measurements were measured for all electrodes and interconnect materials as a function of temperature to 1000 °C.

Evaluation of Ni-MLCC and Fabrication of Ni Thin Electrode by used Ni Nano powder

In order to obtain thinner Ni electrode layers for MLCCs, BaTiO3 organometal resinate was added into Ni paste which consisted of 100nm Ni powders. Ni electrode films were fabricated with the Ni paste added with BaTiO3 organometal resinate, and sintering and electrical characteristics of the film were examined in the present study. The experimental results indicated that addition of BaTiO3 organometal resinate remarkably suppressed the sintering of the Ni electrode films, i.e., no abnormal grain growth was observed on Ni electrode films with BaTiO3 organometal resinate. In addition, MLCCs with 10stacked layers was experimentally fabricated. And the capacitance, the dielectric loss and insulating resistance of MLCCs were measured. The results indicate that even when the of BaTiO3 organometal resinate added is, the electrical characteristics of the MLCCs are not impaired regardless of the nano-size of the Ni particles. An addition of BaTiO3 organometal resinate was found to be extremely effective for obtaining thin electrode layers.

Hybrid Electro-Active Papers of Cellulose and Carbon Nanotubes for Bio-Mimetic Actuators

Electro-Active Paper (EAPap) materials based on cellulose are attractive for many applications because of their low voltage operation, lightweight, dryness, low power consumption, bio-degradability. The construction of EAPap actuator has been achieved using the cellulose paper film coated with thin gold electrode layers. This actuator showed a reversible and reproducible bending movement. In order to improve both force and displacement of this, efforts are made to construct hybrid EAPap actuators using cellulose paper coated with carbon nanotubes (CNT). To coat the CNT, single-walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT) are dispersed in polyaniline (PANI) matrix, and the solution is coated on the EAPap by using a spin coater. It is expected that the use of CNT can improve the force output by enhancing the stiffness of the hybrid EAPap actuator. Furthermore, the presence of the PANI may improve the actuation performance of the EAPap material. The performance of hybrid EAPap actuators is tested in an environmental chamber in terms of free displacement, blocked force and electrical power consumption. The performance of hybrid actuators is investigated for bio-mimetic applications.

Silver-cobalt bimetallic particles for oxygen reduction in alkaline media

The kinetics of the oxygen reduction reaction (ORR) was studied on ultra thin layer electrodes formed by bimetallic Ag-Co nanoparticles dispersed on a carbon powder (Ag-Co/C) in KOH electrolyte. The morphological features of the materials were studied by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Cyclic voltammetry and steady state polarization measurements for the ORR were obtained using the rotating ring/disk electrode (RRDE) technique. TEM measurements for the bimetallic Ag-Co/C catalysts showed a heterogeneous crystallite size distribution and, together with XRD, suggested the presence of a segregated phase of cobalt, mainly as Co 3O 4. The characterization of the materials by XRD also showed a negligible decrease in the Ag face centered cubic (fcc) lattice parameter, which was ascribed to a negligible Co insertion into the Ag structure. Levich plots obtained from rotating disk electrode data have shown a higher number of electrons for the Ag-Co/C materials, compared to Ag/C. The polarization results showed higher activity for the ORR on Ag-Co/C materials in comparison to Ag/C.

Two-dimensional analysis of the effect of an electrode layer on surface acoustic waves in a finite anisotropic plate

The effect of a metal layer over an elastic substrate on surface acoustic wave propagating in the structure can be evaluated precisely for semi-infinite solids and infinite plates, but there is no accurate analytical solution if the finite size of the plate has to be considered. By expanding displacements with eigensolutions of surface acoustic waves in a semi-inifite solid, a set of two-dimensional equations similar to the Mindlin plate theory are obtained. Then for a thin electrode layer, the effect is considered through the approximation of displacements in the metal layer with the ones in the substrate, and an integration over the thickness incorporated the properties of the metal layer into equations through the modification of material properties with the decaying indices of surface acoustic waves and the thickness of the metal layer. Using AT-cut quartz crystal as the substrate, we present the effect of silver electrode layers of finite thickness on the phase velocity of propagating surface acoustic waves.

Cycle-life testing of large-capacity lithium-ion cells in simulated satellite operation

We are conducting cycle-life testing of 10–100 Ah-class lithium-ion cells in a simulated satellite operation at the Japan Aerospace Exploration Agency (JAXA). This paper reviews the latest test results of these lithium-ion cells. Thus far, we have verified impressive life performance exceeding 30,000 cycles in a simulated low-earth-orbit (LEO) mode and 1800 cycles in a simulated geostationary-earth-orbit (GEO) mode for some of these cells. We optimized the thickness of the electrode layer to suppress cell-internal impedance and found that a lithium-ion cell with a thin electrode layer exhibited promising cycling performance in a simulated LEO operation. Since the electrode material is an important factor affecting the charge–discharge behavior of a lithium-ion cell, we also compared the cycling performance of lithium-ion cells with different cathode materials.

Electrochemical and spectroelectrochemical behaviour of Np(VI) ions in nitric acid solutions

SummaryElectrochemical and spectroelectrochemical has been used to investigate the behaviour of neptunium (VI) in 1 ∼ 8 M HNO3solutions. The electrochemical reactions of Np(VI) ions were found to occurquasi-reversibly. The formal redox potentials (E°) for Np(VI)/Np(V) couples were determined to be +0.906, +0.908, +0.909, +0.902, +0.896, +0.895, +0.888, and +0.884 V (vs. Ag/AgCl) for Np(VI) ions in 1, 2, 3, 4, 5, 6, 7, 8 M HNO3solutions, respectively. The reduction processes of Np(VI) ions were followed spectroelectrochemically by using an optical transparent thin layer electrode cell. It was found that the absorption spectra measured at the applied potentials from +1.10 to +0.60 VversusAg/AgCl reference electrode redox couple for Np(VI) in HNO3solution have clear isosbestic points. These results indicate that the only reduction product of Np(VI) is Np(V), which is of considerable stability in HNO3solutions.

Electrochromic devices based on wide band-gap nanocrystalline semiconductors functionalized with mononuclear charge transfer compounds

A series of ruthenium and iron mononuclear complexes were prepared and their spectroeletrochemical behavior characterized on Optically Transparent Thin Layer Electrodes (OTTLE) and on Fluorine Doped SnO 2 (FTO) conductive glasses coated with Sb-doped nanocrystalline SnO 2. These systems display a reversible electrochemical response and offer potential application in electrochromic devices. On SnO 2 films distinct spectral changes are observed in a narrow potential range (−0.5/0.9 V vs SCE) with switching times of the order of 0.8 s.

Electrochemical Mass Spectroscopic and Surface Photovoltage Studies of Catalytic Water Photooxidation by Undoped and Carbon-Doped Titania

Carbon-doped TiO2, demonstrated as an efficient photocatalyst in visible light photooxidation of organic compounds, was prepared with different doping concentrations and investigated via differential electrochemical mass spectroscopy (DEMS) and capacitive surface photovoltage (SPV) measurements in the form of thin layer electrodes. In all cases the total photocurrent as well as the surface photovoltage of the doped materials decreased markedly in relation to the undoped one. No detectable oxygen evolved from the doped electrodes in acidic solution under UV-light excitation. Since an oxidation of formic acid is still apparent, it is concluded that this oxidation occurs via isolated, catalytically poorly active trap states within the forbidden energy region. The existence of these states is confirmed by capacitive SPV measurements.

Layer by layer preparation of electrodes with defined thickness by multiple use of the SIC coating process

By using a coating process, so-called substrate induced coagulation (SIC), thin layer electrodes of defined thickness can be prepared. After a short introduction in the process itself, first results with the electrode material Li 4Ti 5O 12 are presented. Future application areas and the advantages of electrodes made by the SIC process are discussed.

Electrochemical performance of dispersed Pt-M (M =V, Cr and Co) nanoparticles for the oxygen reduction electrocatalysis

The kinetics of the oxygen reduction reaction (ORR) was studied in KOH electrolyte on ultra thin layer electrodes formed by Pt-V, Pt-Cr and Pt-Co electrocatalysts dispersed on a carbon powder (Pt-M/C). The electronic and structural features of the materials were studied by in situ XANES (X-ray Absorption Near Edge Structure) and EXAFS (Extended X-ray Absorption Fine Structure). Cyclic voltammograms and steady state polarization curves for the ORR were obtained using the rotating ring/disk electrode technique. The XANES results for the composites in the oxidized state have shown an increase of the occupancy of the Pt 5d band while the EXAFS analyses showed some reduction of the Pt-Pt interatomic distance in the different metal alloys compared to Pt/C. The electrochemical measurements indicated that the 4-electrons mechanism is mainly followed for the ORR in these platinum alloys. The highest electrocatalytic activity was shown by the Pt-V/C alloy, after treated at 850 ºC under hydrogen atmosphere.

Electrolytic molybdenum oxides in lithium batteries

Nonstoichiometric molybdenum oxides (e-MoxOy) were synthesized by cathodic reduction of aqueous ammonium and sodium molybdate solutions. Surface morphology of electrolytic (e) deposits, the chemical composition, crystal lattice structure, and the characteristics of electrochemical Li+ intercalation for such synthesized oxides were determined by the cation composition of molybdate solution and the conditions of deposit annealing. The electrochemical intercalation of Li+ ions in these Mo-oxides was investigated in thin-layer “ballast-free” electrodes, as a pasted соmposite cathode in lithium batteries, and as an anode in lithium-ion batteries, with liquid organic and polymer electrolytes. The reversible discharge capacity of e-Mo4O11 synthesized from ammonium molybdate electrolyte in thin-layer ballast-free electrodes can exceed 225 mAh g−1 for more than 170 cycles.

Electrolytic Iron Sulfide Products in Lithium Batteries

A technology for electrolytic production of iron sulfide compounds applicable in thin-layer lithium batteries is developed. Physicochemical and structural properties and the surface morphology of compounds are studied by x-ray diffraction and thermal analyses, absorption IR spectroscopy, and atomic force microscopy. Specific discharge characteristics of compounds in thin-layer compact nonballast and paste electrodes of model lithium power sources are determined. The discharge capacity of compounds in thin layers weighing 1.0–7.5 mg cm–2 galvanostatically cycled in electrolyte PC, DME, 1 M LiClO4 at room temperature stays at 200–320 mA h g–1 for 40–50 cycles.

Use of multivariate curve resolution analysis in the spectroelectrochemistry of 9,10-anthraquinone reduction in dimethylformamide solution

A multivariate curve resolution analysis has been conducted to deconvolute the spectroelectrochemical data of 9,10-anthraquinone (AQ) reduction. The experiments were carried out in dimethylformamide solution containing small amounts of benzoic acid as a proton source at an optically transparent thin layer electrode (OTTLE). Two electrochemical techniques, namely a potential step method and chronoabsorptiometry were employed. In the former, the absorbance spectra of anthraquinone solutions at different applied potentials were recorded, and in the latter technique, a −1.90 V potential was applied to the OTTLE and the absorbance spectra of the solution were recorded at different time intervals. For both techniques, factor analysis revealed that three chemical components coexist in the system, which can be attributed to AQ − , AQH − and AQ 2−. By using a multivariate curve resolution analysis, the concentration profiles and pure spectra of the components were determined. The results of the potential step method revealed that the maximum amount of AQ − is produced at −1.25 V, and application of more negative potentials causes an decreased amount of AQ − at the expense of the evolution of AQH −. Finally, the AQ 2− species is produced at −1.6 V. The chronoabsorptiometric results showed that AQ − is not stable at 1.9 V and rapidly converts to AQ 2−.

Spectroelectrochemical Determination of the Redox Potential of P700 in Spinach with an Optically Transparent Thin-layer Electrode

Abstract Optimization of experimental conditions for spectroelectrochemistry with an optically transparent thin-layer electrode allowed us to determine the redox potential of spinach P700, the primary electron donor of photosystem I, to be +469 mV vs. SHE with significantly high reproducibility (±2 mV for 12 independent samples).

A New Optically Reflective Thin Layer Electrode (ORTLE) Window: Gold on a Thin Porous Alumina Film Used to Observe the Onset of Water Reduction

AbstractThe fabrication and unique characteristics of a new type of thin layer electrode, an optically reflective thin layer electrode (ORTLE), are described. The electrode was fabricated by the anodization of a thin layer of aluminum sputtered onto a plain glass microscope slide to create a 750 nm‐thick porous alumina film. A thin film of gold was then sputtered atop the porous and transparent alumina film. The gold layer remained porous to allow solution into the pores but was optically thick and reflective. Reflectance measurements made through the microscope slide did not interrogate the bulk solution, but show spectral features that shift with the optical properties of the material filling the pores of the alumina film. A simple series of experiments, in which the potential of the ORTLE was stepped negatively to various values in an aqueous sodium sulfate solution, shows that interference fringes shift measurably in the ORTLE spectrum at potentials several hundred millivolts positive of the potential at which gas evolution was visible to the naked eye.

Fabrication and Evaluation of Ni-MLCC Used of New BaTiO3 Resinate

In order to obtain thinner Ni electrode layers for MLCCs, BaTiO3 organometal resinate was added into Ni paste, which consisted of 0.2 μm or 0.4 μm Ni powders. Ni electrode films were fabricated with the Ni paste added with BaTiO3 organometal resinate, and sintering and electrical characteristics of the film were examined in the present study. The experimental results indicated that addition of BaTiO3 organometal resinate as small as 1 mass% remarkably suppressed the sintering of the Ni electrode films, i.e., no abnormal grain growth was observed on Ni electrode films with BaTiO3 organometal resinate. In addition, MLCCs with 10-stacked layers was experimentally fabricated. The results indicate that the continuity of electrodes characteristics of the MLCCs are not impaired regardless of the size of the Ni particles. An addition of BaTiO3 organometal resinate was found to be extremely effective for obtaining thin electrode layers.

Electrochemical and spectroelectrochemical properties of neptunium(VI) ions in nitric acid solution

Electrochemical behavior of NpO22+ on platinum (Pt) and glassy carbon (GC) electrodes have been studied in an aqueous 3M HNO3 solution using cyclic voltammetry and spectroelectrochemical method. The NpO22+ species was found to be reduced to Np(V) quasi-reversibly with the formal redox potential of +0.907 V (Pt) and +0.909 V (GC). The reduction process of NpO22+ in an aqueous 3M HNO3 solution was also followed spectroelectrochemically by using an optical transparent thin layer electrode cell. It was found that the absorption spectra measured at the applied potentials in the range of +1.05 to +0.65 V have isosbestic points at 1051 and 1124 nm and the evaluated electron stoichiometry is 0.93. These results indicate that the reduction product of NpO22+ is NpO2+. Further details for reaction mechanism of Np(VI) are discussed on the basis of digital simulation of the experimental cyclic voltammograms.

A novel dual thin-layer flow cell double-disk electrode design for kinetic studies on supported catalysts under controlled mass-transport conditions

We present a novel dual thin-layer flow cell double-disk electrode design, which due to its high collection efficiency in combination with a reasonable time resolution allows highly sensitive measurements of electro-active species generated during electrochemical reactions on the working electrode. Most important, it allows for rapid changes of the electrolyte during the measurements, which in combination with a thin-film electrode, where an inert glassy carbon substrate is covered by a thin film of carbon-supported noble metal catalyst, makes it particularly useful for kinetic studies on electrocatalytic fuel cell reactions under realistic conditions (continuous reaction, continuous electrolyte flow) and on realistic materials (supported catalysts). The performance of the set-up and its suitability for kinetic studies, in particular for transient experiments involving rapid electrolyte exchange, are demonstrated in potentiodynamic and transient potentiostatic measurements for the oxygen reduction reaction on carbon-supported Pt catalysts and, for comparison, on Pt-free Vulcan carbon supports.

Spectroelectrochemical Measurements at Colloidal Au Multilayer Optically Transparent Electrodes

AbstractApplication of thin colloidal Au multilayers on glass substrates as optically transparent electrodes is reported herein. Evaluation of the electrode by scanning electron microscopy and as an optically transparent thin layer electrode (OTTLE) illustrate its use for spectroelectrochemical applications. A spectroelectrochemical Nernst plot acquired for the oxidation of o‐tolidine yielded a value of E°=0.605 V (vs. Ag/AgCl) and n=1.88. Both of these values are in excellent agreement with previously published values obtained using a traditional Au minigrid OTTLE. The colloidal Au multilayer electrode is expected to offer many advantages over the minigrid OTTLE in specific applications. These advantages include direct control over microscopic surface topography, large electrochemical surface area, applicability to many different electrode geometries, and increased microscopic surface roughness for SERS and SPR applications.