Electrochemical Measurement System Research Articles

Design of a portable electrochemical impedance spectroscopy measurement system based on AD5941 for lithium-ion batteries

Electrochemical impedance spectroscopy (EIS) is an important indicator of state of health (SOH) for Lithium-ion batteries (LIBs), but its measurement relies mainly on electrochemical workstations that are costly and cannot be used for on-site testing. This paper designs a portable EIS measurement system based on the high-precision impedance converter chip AD5941, which utilizes a wide-frequency constant current source as the excitation signal and detects the LIB's response voltage signal to obtain EIS data ranging from 0.1 Hz to 2 kHz. In addition, a software interface based on LabVIEW is developed for real-time graphically displaying the EIS information. EIS measurement experiments are performed on a NCR-18650B LIB at different charge states in both single-frequency mode and frequency-sweep mode using the newly-designed EIS measurement system. The results show that in single-frequency mode, the impedance measurement error at 1 kHz is below 2.8 % compared with a standard single-frequency electrochemical impedance analyzer. In frequency-sweep mode, the Nyquist plot of the LIB is obtained at different charge states and exhibits good repeatability. Moreover, an effective equivalent circuit analysis of the EIS data was performed, which further substantiates the practical utility of the EIS system in providing valuable insights into the battery's electrochemical behavior. Compared to the traditional EIS measurement systems, the proposed EIS measurement system has the advantages of low cost, easy operation and portability, which exhibits promising prospects for on-site EIS applications.

Wireless and Portable Electrochemical Measurement System Integrated with Screen-Printed Immunosensor for VP28 Protein Detection

Wireless and Portable Electrochemical Measurement System Integrated with Screen-Printed Immunosensor for VP28 Protein Detection

Effect of Special Plating Films on Galvanic Corrosion Behavior between Metal and CFRTP

In this study, electrochemical measurements and observations investigated galvanic corrosion behavior between various metals with or without projection-shaped Ni–Cu alloy plating film and carbon-fiber-reinforced thermoplastic (CFRTP) of corroded areas. Stainless steel, aluminum alloy, and CFRTP plates were prepared. Ni and Ni–Cu alloy electroplating were performed on the stainless steel plate. Electroless zinc plating, Ni, and Ni–Cu alloy electroplating were performed on the aluminum alloy plate. The galvanic current between the metal and CFRTP plates was measured using an electrochemical measurement system. The test solution was 0.06 mol/L NaCl aqueous solution. For Stainless steel/CFRTP, the galvanic current flow was negligible with and without the Ni–Cu alloy plating film. For aluminum alloy/CFRTP without the Ni–Cu alloy plating film, the galvanic current ranged from-80 to-120 μA/cm2 at a test temperature of 60°C. For aluminum alloy with the Ni–Cu alloy plating film, the galvanic current ranged from-60 to-80 μA/cm2. The galvanic current for the aluminum alloy plate with Ni–Cu alloy plating was lower than that of the aluminum alloy plate without Ni–Cu alloy plating film. The result suggests that the formation of the Ni–Cu alloy plating on the aluminum alloy improves corrosion resistance.

Nanofilm-enhanced electrochemical DNA sensing: a breakthrough for yellow rust detection in wheat

This study showcases the development of a genosensor utilizing a nanoscale NiO thin film. The genosensor is constructed on a glass substrate coated with tin-doped indium oxide (ITO) and is designed for the specific detection of DNA sequences associated with Puccinia striiformis f. sp. tritici (Pst), the causal agent of wheat yellow rust. The detection process relies on the utilization of methylene blue (MB) as an electrochemical indicator, with NiO acting as the matrix and the electrochemical measurement system serving as the transducer. Various single-stranded DNA oligonucleotide sequences related to Pst pathogenesis are employed as probes to enable sensing. The electrochemical response of the nanoscale bioelectrode is characterized and studied using two distinct electrochemical techniques, cyclic voltammetry (CV) and differential pulse voltammetry (DPV), in conjunction with a potentiostat. The detection ranges spans from 40 pg μl−1 to 115 ng μl−1, demonstrating a linear correlation with exceptional precision. The absence of DNA-based biosensors for the detection of Puccinia striiformis f. sp. tritici (Pst) has prompted the need for a new method to address the limitations associated with previously reported technologies. Although surface plasmon resonance (SPR) immunoassays have been reported for Pst detection, the development of DNA-based biosensors specifically tailored for Pst detection remains unexplored. Introducing a novel method aims to overcome the challenges and shortcomings of existing techniques, providing a new approach to detect and combat the devastating effects of Pst on wheat crops. By leveraging the advantages of DNA-based biosensors, such as their sensitive and precise detection capabilities, this new method seeks to enhance the accuracy and efficiency of Pst detection, ultimately contributing to the development of effective strategies for disease management and crop protection. The developed nanoscale electrochemical DNA sensor offers outstanding sensitivity, extended shelf life, and reliable recovery, effectively minimizing the likelihood of obtaining erroneous results. A significant highlight of this study is the first-time utilization of conserved sequences associated with pathogenesis in selected Pst strains for the development of a nanoscale genosensor.

Electrolyte/Electrode Interface Reaction in Polysulfides Insoluble Lithium-Sulfur Battery Using Li-Glyme Solvate Ionic Liquid

Lithium-Sulfur (Li-S) battery is attracting attention as a new generation secondary battery. However, one of the major problems is dissolution of discharge products of lithium polysulfides (Li2Sn: n = 1, 2, 4, 6 and 8) that cause the self-discharge. Solvate ionic liquids (SIL), which consist of a solvate ion and its counter ion, are a subclass of ionic liquids. Li-Gn SIL is yielded by equimolar mixing lithium bis-(trifluoromethanesulfonyl)amide (LiTFSA) and glyme, an oligoether such as triglyme and tetraglyme (Gn : CH3O-(CH2CH2O) n -CH3, n = 3, 4). Watanabe and Dokko et al. [1] reported that the Li-glyme SIL had low solubility of the polysulfides, and proposed polysulfides insoluble Li-S batteries using these electrolyte solutions. Recently, a sulfolane-based super-concentrated electrolyte solution (SCES) also exhibits low solubility of the polysulfides and has been applied to Li-S battery [2]. Both of Li-Gn SIL and the SCES are polysulfide insoluble electrolytes, however, the Li-S batteries with the SCES has better battery performance than that with Li-Gn SIL, implying that the different discharge reaction paths. In this contribution, in situ electrochemical impedance spectroscopy (EIS), which can acquire charge-discharge curves and impedance spectra simultaneously, is applied to the Li-S battery using the Li-Gn SIL to obtain further insight into the discharge behavior.A positive electrode slurry was obtained by mixing a sulfur S8, a Ketjen black (KB, EC600JD, Lion Corporation) and a carboxymethyl cellulose (CMC2200, Daicel) at a weight ratio of 60 : 30 : 10. The slurry was spread on an Al foil to obtain a KB-S composite electrode. The typical loading of the sulfur was 1.0 mg cm-1. A negative electrode and a separator were used a lithium metal foil (Honjo Metal) and a glass separator (GA-55, Advantec), respectively. The Li-Gn SIL electrolyte solution was prepared by mixing LiTFSA, G4 and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (HFE) as the molar ratio of 1 : 1 : 4. The Li-S batteries were assembled using the CR 2032 coin-type cell in an Ar-filled glove box. In situ EIS measurements were conducted at different C-rate under constant-current discharging/charging condition using an electrochemical measurement system (SP-150, BioLogic). The current values were 336 and 84 μA. The DC current was superimposed with a small AC current adjusted so that the response voltage amplitude did not exceed 10 mV. The measurements were carried out in the frequency range from 500 kHz to 10 mHz.The voltage drop is observed at the DOD = 20-35 %, in the discharge profile measured at the high C-rate (336 μA), whereas that measured at the low C-rate (84 μA) has no voltage drop. The compensation for the changes over time [3,4] was performed on the obtained impedance spectra to determine instantaneous impedance spectra at a specific DOD (depth of discharge). Two capacitive semicircles and a straight line are observed for all of the investigated systems. The semicircle in the high frequency range (< 10 Hz) is asymmetrical, as if two semicircles in the high frequency range from 500 kHz to 1 kHz and in the middle frequency range from 1 kHz to 10 Hz are overlapped. For the high C-rate, the diameter of the semicircle in the middle frequency range increases with increasing DOD and remarkably increases at DOD = 20-35 %. By contrast, in the low C-rate, the diameter does not change during discharging. This semicircle is assigned to the charge transfer resistance of the negative electrode. According to the previous studies [5, 6], when the charge transfer reaction of lithium is faster than the diffusion rate of G4, the solvation structure changes due to the lack of G4 coordinating to Li+. This solvation structure change causes suppression of Li+ elution to increase the charge transfer resistance of the negative electrode. References 1) K. Dokko et al., J. Electrochem. Soc., 160, A1304-A1310 (2013).2) A. Nakanishi et al., J. Phys. Chem. C, 123, 14229-14238 (2019).3) Z. B. Stoynov et al., J. Electroanal. Chem., 183, 133-144 (1985).4) M. Itagaki et al., J. Power Sources, 135, 255-261 (2004).5) N. Serizawa et al., J. Electrochem. Soc., 160(9), A1529–A1533, (2013).6) A. Miki et al., J. Mater. Chem. A, 9, 14700–14709, (2021).

Voltammetric Determination of Trimethoprim Using a Glassy Carbon Electrode Modified with Printex(6L) Carbon and Gold Nanoparticles

This work proposes a simple, fast and low-cost voltammetric method for the determination of trimethoprim at low concentrations in an analytical and real matrix (river water sample, bovine serum and synthetic urine). For this, a glassy carbon electrode was modified with Printex(6L) carbon and gold nanoparticles in a chitosan film crosslinked with epichlorohydrin. After that, the electrochemical measurement system contained a solution of phosphate buffer at pH 4.0 with commands for the square wave voltammetry technique. The results achieved showed a limit of detection equal to 12.4 nmol L−1 and a linear concentration range from 0.20 to 6.0 μmol L−1. The sensor selectivity was tested in the presence of various electroactive molecules, and the results showed that the detection of TMP in the presence of possible interferents was not masked. In addition, the applicability of the AuNPs–Printex(6L)–CTS:EPH/GCE sensor was also verified in synthetic samples of urine, bovine serum and river water through standard addition and recovery tests. Finally, the results of this analytical proposal portray a simple, fast and efficient method for the detection of TMP in different matrices.

Preparation of Pie-Shaped CoMoO4 with High Capacitive and Photocatalytic Properties by a Solvothermal Method

This paper reports a method for fabricating pie-shaped CoMoO4 nanomaterials. The morphologic characterization and phase analysis showed that the prepared material was CoMoO4 and presented a pie-shape. Pie-shaped CoMoO4 electrode materials possess high specific capacitance in three-electrode electrochemical measurement systems. When the current density is 1 A/g, the specific capacitance reaches 1902 F/g. In addition, it has good cycle stability. With 10,000 charge–discharge cycle experiments at a current density of 15 A/g, pie-shaped CoMoO4 has a specific capacity retention ratio of 99.5%. In addition, the CoMoO4//CNTs device can provide a maximum energy density of 55.6 Wh/kg (1 A/g) and a maximum power density of 10,900 W/kg (15 A/g), showing good electrochemical performance. The photocatalytic properties of pie-shaped CoMoO4 were also studied. The results show that the degradation rates of MO (methyl orange), MB (methyl blue), and CR (Congo red) can reach 97.8%, 98.8%, and 99.6% at 100 min, 40 min, and 65 min, respectively. The material has good photocatalytic performance. The excellent performance of pie-shaped CoMoO4 indicates that the electrode material has potential application scenarios in electrode materials and photocatalysis.

Fabrication of a Fundamental Electrochemical Measurement System for an Electrochemical Sensor

A fundamental electrochemical measurement system for an electrochemical sensor was built using a microcomputer control. It is crucial that the electrochemical sensor results can be used for both qualitative and quantitative analysis. These fundamental data are estimated by cyclovoltammetry (CV) and chronoamperometry (CA) measurements, which are major measurement methods in the electrochemical engineering field. The CV measurement function has already been built in our previous study and its functionality was confirmed to be nearly identical to that of a commercially available potentiostat. The CA measurement function was implemented in this study to allow our system to perform quantitative analysis of substances. Further, we started fabricating working electrodes. Therefore, we learned how to construct a high-performance and low cost self-made electrochemical sensor.

Performance and Durability of Solid Oxide Electrolysis Cell Air Electrodes Prepared By Various Conditions

Introduction Fuel electrode materials are important for achieving higher performance and durability of Solid Oxide Fuel Cell (SOFC), Solid Oxide Electrolysis Cell (SOEC), and Reversible Solid Oxide Cells (r-SOCs). On the other hand, the air electrode also faces performance and durability issues. For example, the diffusion of Sr ions from the air electrode materials has been reported.1, 2 In SOECs, if electrolysis can be performed at a thermoneutral potential balancing heat absorption by electrolysis and heat generation by the internal resistance of the electrolysis cell, hydrogen can be generated theoretically without heat supply. The purpose of this study is to evaluate the electrochemical performance and durability of the SOECs by conducting electrolysis performance tests of LSCF-based air electrodes with different preparation conditions, and electrolysis durability tests at the thermoneutral potential. Experimental Each test was conducted using a cell with a scandia-stabilized zirconia electrolyte (ScSZ, 200 µm thick) as a substrate. For the fuel electrode, Ni-GDC co-impregnated fuel electrode was used3. A mixture of Ni(NO3)2･6H2O, Gd(NO3)3･6H2O, and Ce(NO3)3･6H2O was impregnated into the porous LST-GDC framework, a mixture of LST powder (La0.1Sr0.9TiO3) and GDC powder (Gd0.9Ce0.1O₃). LSCF, (La0.6Sr0.4)(Co0.2Fe0.8)O3, was used for the air electrodes. GDC was inserted between the LSCF layer and the electrolyte plate as a buffer layer. In fabricating air electrodes, four types of air electrodes were applied, at shown in Table 1. For the electrochemical measurements of the air electrodes, Pt reference electrode was attached to the electrolyte on the fuel electrode side, and the voltage terminals of the electrochemical measurement system were connected between the reference electrode and the air electrode to measure air electrode voltage.In the performance tests, the voltage (potential) and impedance of the air electrode were measured at operating temperatures of 800°C, 750°C, and 700°C. In the durability tests, the air electrode was maintained at thermoneutral potentials at 800°C and 700°C (1.286 V and 1.283 V, respectively), and the voltage and impedance of the air electrodes were measured before and after the durability tests to evaluate the degradation of the air electrodes. Results and discussion Figure 1 shows the air electrode voltage obtained from the performance tests at each operating temperature for the four types of air electrodes shown in Table 1. First, regarding the dependence of the electrolysis performance on operating temperature, an increase in air electrode voltage (degradation of the air electrode) was found at 800°C.The increase in air electrode voltage with current density was almost linear, but at lower operating temperatures, the increase in air electrode voltage at lower current densities becomes larger. In other words, the I-V curve was rather ohmic at 800°C, but non-ohmic at 700°C.Figure 2 shows the results of an 80-hour durability test at different temperatures. The current density of the cell corresponding to the thermoneutral potential was -0.298 Acm-2 when operated at 800°C and -0.018 Acm-2 when operated at 700°C.The degradation rate was calculated from the difference in air electrode voltage before and after the performance and durability test at these current densities: 0.172% at 800°C and 0.792% at 700℃. The degradation rate increased as the operating temperature decreased in the SOEC mode, despite the low current density. Microstructural observation of the air electrode after the durability test showed that Sr diffused to the LSCF/GDC interface similar to SOFCs mode4, and that the diffusion of Sr was accelerated at 700°C. In addition, Co diffusion was also observed. Such diffusion may occur during LSCF firing process and/or during SOEC operation. More detailed investigation is in progress. Acknowledgements This research was supported in part by NEDO (New Energy and Industrial Technology Development Organization). We thank all parties involved. References (1) V. Subotić, S. Futamura, G. F. Harrington, J. Matsuda, K. Natsukoshi, and K. Sasaki, J. Power Sources, 492, 229600 (2021).(2) S. P. Simner, M. D. Anderson, M. H. Engelhard, and J. W. Stevenson, Electrochem. Solid-State Lett., 9 A478 (2006).(3) K. Natsukoshi, K. Miyara, Y. Tachikawa, J. Matsuda, S. Taniguchi, G. F. Harrington, and K. Sasaki, ECS Trans., 03, 203 (2021).(4) S. Kanae, Y. Toyofuku, T. Kawabata, Y. Inoue, T. Daio, J. Matsuda, J,-T. Chou, Y. Shiratori, S. Taniguchi, and K. Sasaki, ECS Trans., 68, 2463 (2015). Figure 1

Electrochemical antioxidant capacity measurement: a downsized system and its application to agricultural crops.

An on-site electrochemical antioxidant capacity measurement system was developed using a screen print electrode (SPE) and circuit tester. The antioxidant capacities of eight antioxidants were evaluated with the handheld electrochemical antioxidant capacity measurement system to compare with those measured with spectroscopic methods, namely, oxygen radical absorbance capacity (ORAC) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assays, as well as the reported electrochemical method with three conventional electrodes (a glassy carbon electrode, Ag/AgCl electrode and platinum wire electrode) and a potentiostat. Additionally, the potential shifts were proportional to the logarithm of the antioxidant concentration, which obeyed the Nernstian equation. Moreover, the antioxidant capacities of extracts from vegetables (green pepper, ginger and eggplant) were measured with a handheld electrochemical system. Each measurement was finished in only ca. 3min. The electrochemically obtained antioxidant data were comparable to those from DPPH free-radical scavenging assays and superoxide anion scavenging activity (SOSA) assays, as well as the total phenolic compound content.

Observation of Oxygen Bubble Growth near Anode Catalyst Electrode in PEM Water Electrolyzer

Water electrolysis technology is expected to be essential to build a hydrogen energy system. In particular, proton exchange membrane water electrolyzer (PEMWE) has attracted much attention because of its advantages such as the ability to downsize the equipment and produce high-purity hydrogen [1]. Improving the electrolysis efficiency of PEMWE is needed for future commercialization. One of the serious problems to improve the electrolysis efficiency is the oxygen concentration overpotential [2]. The oxygen concentration overpotential is considered to be not only caused by the generated oxygen bubbles but also by the dissolved oxygen near the anode catalyst electrode. Therefore, it is necessary to investigate the concentration distribution of dissolved oxygen near the anode catalyst electrode and to clarify the mechanism of the oxygen concentration overpotential. Although there are some reports about oxygen bubbles in PEMWE [3], there are few reports which investigate the dissolved oxygen. In this study, due to investigate the existence of the dissolved oxygen, the oxygen bubble behavior near the anode catalyst electrode was observed by using a high-speed camera and measured the oxygen bubble size change.A single cell with a 1 cm2 active area was used and a transparent acrylic plate was set to the side face of the cell for observing bubbles. Nafion-117 was used as the PEM, and IrOx and Pt/C were used as the anode and the cathode catalysts, respectively. A sintered Ti with Pt plating was used for the anode porous transport layer (PTL) and a carbon paper (TGP-H-060) was used for the cathode PTL. A high-speed camera (Photron, FASTCAM Mini AX100) and two LED lighting apparatuses (Hayashi-Repic, LA-HDF108DA) were used for visualizing. The resolution was 1024 × 1024 pixel, the pixel size was 3.2 μm, and the framerate was 4000 fps. An electrochemical measurement system (Bio-Logic, SP-300) was used for the power supply. Visualization was performed during electrolysis at 30 mA/cm2 with current control.From the observation of oxygen bubble behavior, the diameter of oxygen bubbles continued to increase until the bubbles left a certain distance even after detached from the anode catalyst. It was considered that the generated oxygen dissolved into the water and there were oxygen supersaturated areas near the anode catalyst electrode.Reference[1] M. Carmo et al, Int. J. Hydrogen Energy, 38 (12), 4901-4934 (2013)[2] J. Kai et al, J. Electrochem . Soc., 166 (4), F246-F254 (2019)[3] P. J. Kim et al, J. Electrochem . Soc., 167, 124522 (2020)AcknowledgmentsThis study was based on results obtained from a project (JPNP14021) commissioned by the New Energy and Industrial Technology Development Organization (NEDO) and also partly supported by JSPS KAKENHI Grant Number 19J20495.

Scalable and controllable fabrication of CNTs improved yolk-shelled Si anodes with advanced in operando mechanical quantification

Scalable and controllable fabrication of CNT-supported yolk-shelled Si/C anodes with advanced in operando mechanical quantification using a new electrochemical transmission electron microscope measurement system.

Visualization of Bubble Behavior on Hydrophobic Coated CL in PEM Water Electrolysis Cell

Due to the need for a new energy infrastructure, water electrolysis technology is receiving increased attention (1), (2). One of the serious problems is management of generated oxygen bubbles which inhibit water supply to the CL. Therefore, bubble behavior was observed on three types of CL with hydrophilic and hydrophobic surface by using a high-speed camera. A single cell, shown in Fig. 1, was used for observing oxygen bubble behavior. Nafion-117 was used as PEM, and IrOx and Pt/C was used anode and cathode catalyst, respectively. Sinterd Ti with Pt plating was used for anode porous transport layer (PTL). Three types of PTFE coated CL were prepared: (a) no coating, (b) coated all and (c) coated half. High-speed camera (Redlake MASD, HS-1), magnifying glass (Hirox, cx-10c) and objective lens (Hirox, OL-35) were used. Electrochemical measurement system (Bio-Logic, SP-240) was used for applying voltage, and the voltage sweep was performed at a rate of 4 mV/s until the cell voltage turned from 0 V to 2.5 V. The current density at voltage of 2.5 V was about 4200 mA/cm2 for CL (a), 1200 mA/cm2 for CL (b) and 3700 mA/cm2 for CL (c). A big bubble covering entire PTL hole was visualized in Fig. 2 (b). In Fig. 2 (c), smaller bubbles appeared from left PTFE uncoated area were merged into a bigger bubble, which stayed on right PTFE coated area. The size of bubbles staying on the edge of PTL-holl in Fig. 2 (a) was smaller than those of (b, c). The results may suggest that the CL (b) deteriorated the cell performance because of the bubble covering entire reaction area. From this experiment, we could control stagnation of bubbles on CL by PTFE treatment. There may be some possibilities that controlling bubble stagnation make some differences on cell performance.Acknowledgements: This study was based on results obtained from a project (JPNP14021) commissioned by the New Energy and Industrial Technology Development Organization (NEDO).Reference:(1) G. Bender, et al, Int. J. Hydrogen Energy, 44 (2019), 9174-9187(2) S. Mitsushima et al, ECS Meeting s, MA2019-02 (2019), 1715. Figure 1

Development of High Corrosion Resistance Surface Treatment for Stainless Steels

Polymer electrolyte fuel cells (PEFC) is energy converter with high efficiency and operates at low temperatures of 80oC, thus it gains attention as an automotive power plant. Stainless steels, which could be used as a PEFC bipolar plate material, can be made very thin1), and has the advantage that the power density of a single cell can be improved. However, it has been reported that the proton conductivity of the electrolyte membrane decreases due to the dissolved iron and chromium ions from the polarized stainless steels due to the current fluctuation during PEFC operation2-3). In this study, the surface treatment method of stainless steels for improving the corrosion resistance was proposed and the electrochemical properties were evaluated.The anodic polarization curve of stainless steels was measured by a three-electrode system using an electrochemical measurement system (HZ-7000, Hokuto). The working electrode was SUS316L with various surface treatments. A platinum wire and a silver-silver chloride electrode were used for counter and reference electrodes. The electrolyte was 1.0 M H2SO4 (pH 3) containing 1 ppm NaCl and 3ppm NaF. and this electrolyte is defined as a PEFC simulation environment. The measurement temperature was 80oC, the potential scan range was from the immersion potential to 1.5 V vs. SSE, and the potential scan rate was 100 mV min-1.Three types of stainless steels were used for the working electrode: I. SUS316L, II. SUS316L treated by chemical conversion (CC SUS316L), and III. SUS316L anodized in electrolyte for chemical conversion (anodized SUS316L). The electrolyte for chemical conversion was a 1:1 mixture of 0.1 M Na2WO4 aqueous solution and 0.1 M Na2MoO4 aqueous solution, and the temperature of electrolyte for chemical conversion was 25oC. In the treatment II, SUS316L was immersed in the electrolyte for chemical conversion for 5 min. In the treatment III, SUS316L was polarized in a electrolyte for chemical conversion at an applied potential of 1.0 V vs. SSE for 5 min.Figure 1 displays the anodic polarization curves of SUS316L with various surface treatments in the simulated PEFC environment. The anodic polarization curve of SUS316L showed passive range from the immersion potential -0.3 V vs. SSE to 0.7 V vs. SSE and small current peak due to the formation of the passive film around 0 V vs. SSE. In the transpassive region at the potential nobler than 0.7 V vs. SSE, the current density region increased sharply. At potentials nobler than 1.3 V vs. SSE, the current density increased sharply due to electrolysis of water. The shape of the anodic polarization curve of the CC SUS316L was almost the same as that of the SUS316L, however, the polarization curve showed a small current density in the passive and transpassive regions. No passive region was observed in polarization curve of the anodized SUS316L. And compared to SUS316L and CC coating SUS316L, the immersion potential shifted to noble and the current density in the transpassive region decreased.References1) F, Barbir. “PEM Fuel Cells Theory and Practice”, Academic Press, 4 (2005), 100, 101.2) A. Pozio, R. F. Silva, M. De Francesco, L. Giorgi, Electrochim. Acta, 48 (2003), 1543-1549.3) H. Wang, J. A. Turner, J Power Sources, 183 (2008), 576-580. Figure 1

Examination of Conductive Properties of ZrO2 Film Formed By Self-Oxidation Method

By forming an oxide film on the surface of metallic zirconium, ZrO2 works as a corrosion resistant film and prevents the permeation of hydrogen. This material is expected to be utilized as a plasma facing material for fusion reactors, because zirconium and ZrO2 have excellent compatibility at high temperature under the redaction atmosphere. Vapor deposition methods such as electron beam vapor deposition and pulse laser vapor deposition are the main methods of forming oxide films on metallic zirconium surfaces. In this study, the self-oxidation method using water vapor was employed as a film forming method, because a dense film of zirconium oxide can be obtained on the surface of metallic zirconium by the heat treatment at 500 °C in water vapor. Although the self-oxidation method using water vapor is promising, the previous reports have been limited yet. An oxide film is formed on the surface of metal Zr by a self-oxidation method in a water vapor atmosphere, and its conductive properties due to the difference in the thickness of each layer of the film are examined.The fine structure of the preparing film was observed with a field emission Scanning Electron Microscope (SEM). The film thickness was determined as the average film thickness from the cross-sectional SEM image using image processing software Image Processing and Analysis in JAVA (Image J). The O/Zr ratio in the film was analyzed by line analysis of an Energy Dispersive X-ray analyzer (EDX). The Crystallinity and formed phase of the film were identified by Electron Back Scatter Diffraction (EBSD) analysis and "grazing incidence X-ray diffraction". impedance measurement was performed using SP-150 electrochemical measurement system of Bio-Logic Sciences Instruments. It was decided to separate the conductivity of each layer by measuring the oxide film prepared by adjusting the film thickness.In the previous studies, it was revealed from the SEM observation of the cross section of the oxide film that the oxide film was not a single layer but a laminated structure whose O/Zr ratio gradually decreases with increasing of the film depth. Therefore, by changing the X-ray incident angle (θ = 1 ~ 12 °) by XRD analysis, we analyzed the change of the formed phase in the thickness direction and found that each phase is not an amorphous phase but a crystalline phase. The sample formed by steam oxidation was subjected to EDS line analysis in the direction perpendicular to the oxide film cross section, and the O/Zr ratio of each layer was measured. It was observed that the atomic ratios of the three kinds of layer, bottom layer, second layer and top layer were observed to be 0.3-0.6, 0.6, and 1.5 or more, respectively. The samples with the various thickness of oxide film were prepared and the specific electrical resistances of each film were measured with the impedance measurements. The electrical conductive properties of each layer were investigated with the fitting of equation whose parameters are the thickness and the specific electrical resistance of each layer.

Connection of CVs and impedance spectra of reversible redox systems, as used for the validation of a dynamic electrochemical impedance spectrum measurement system

With the purpose of fast characterization of electrode reactions, a dynamic electrochemical impedance spectrum (dEIS) measurement system has been assembled which permits the continuous collection of audio-frequency impedance spectra while performing cyclic voltammetry measurements with the usual scan rates of up to 200 mV/s. The performance of this system was tested by analyzing the CV curves and impedance spectra taken simultaneously in ferro-/ferricyanide containing aqueous solutions yielding an experimental demonstration of the connection of the semi-integrated reversible voltammograms and the Warburg coefficients.Graphical abstract

(Invited) High Speed AFM Observation of PEG Additive Behavior Depending on Electrode Potential

1. Introduction Copper electrodeposition has still attracted many attention, since it is applied for the miniaturization of integrated circuits (ICs) and micro electro mechanical systems (MEMS). A damascene process is employed there and a copper wiring controlled on a nanoscale is made. By using a several kinds of additives which is classified into inhibitors, accelerators and levelers, void-free filling electrodeposition is possible. Each additive works by adsorbing on the substrate surface, and their synergistic effect enables the complete filling in the trench. Many studies have been reported on the adsorption mechanism of additives, which is analyzed by in-situ techniques under electrochemical environment [1]. However, since the adsorption of additives occurs at high speed in a fine region, it is very difficult to capture the phenomenon. We could observe the nucleation phenomenon of copper electrodeposition by using high-speed atomic force microscope (HS-AFM) [2, 3]. In this presentation, we will focus on polyethylene glycol (PEG), which is widely used as a copper plating inhibitor, and observe the adsorption / desorption behavior by using HS-AFM in order to investigation the suppression mechanism depending on electrode potential.2. Experimental Experiments were conducted in a three-electrode cell. The working electrode was an Au(100) single crystal (ϕ =3mm, MaTecK), the counter electrode was a platinum wire and the reference electrode was a palladium wire occluded with hydrogen. Prior to each experiment, the single crystal was annealed with a butane burner for a few seconds and then cooled in the atmosphere. The electrolyte was a mixture of 300 ppm PEG aqueous solution (Mw avg ~ 3000, Fujifilm Wako Chemicals) with 1.2 mM hydrochloric acid and 50mM sulfuric acid. Experiments were conducted with an electrochemical measurement system (HZ-7000, Hokuto Denko Co.). The constant potentials from − 0.5 V to 0.1 V were applied at room temperature. The ultra-short cantilevers (NanoWorld AG) were used as the tips for HS-AFM observation. In the present experiment, the scan area was in the range of 500-1000 nm2 and the scanning speed was 1 frame s-1. During the observation, the electrode potential was kept constant value, and the morphological change of the electrode surface was recorde 3. Results and discussion Fig. 1 shows HS-AFM images of PEG adsorption when the electrode potential was -0.10V. Initially at open circuit potential, smooth surface was observed after annealing [Fig. 1 (a)]. PEG adsorption occurred immediately after applying cathodic potential, and line-like PEG structure was formed along the steps edge after 5 s [Fig. 1 (b)]. After 10 s, the adsorbed PEG grew in one direction (as indicated by the arrow) and formed film shape [Fig. 1 (c)]. The growth rate was calculated to be 3.7 nm s-1 from image analysis. This rate was found to be very slow compared to the results of copper deposition in a copper sulfate solution without PEG. After that, the electrode surface was covered with PEG thin film [Fig. 1 (d)]. From the height analysis, the thickness of the PEG film was approximately 4 nm or less, and it was suggested that PEG was adsorbed with a certain thickness by comparing with the literature value [4]. The PEG film was stable at −0.10 V and did not become thicker even after keeping the cathodic potential. REFERENCES [1] Moffat T. P., Wheeler D., Kim S. K., Josell D., J. Electrochem. Soc, 153 (2006) C127.[2] Yoshioka T., Matsushima H., Ueda M., Electrochim. Acta, 302 (2019) 422.[3] Yoshioka T., Matsushima H., Ueda M., Electrochem. Commun., 92 (2018) 29.[4] Walker M. L, Richter L. J, Moffat T. P., J. Electrochem. Soc, 152 (2005) 403. Figure 1

A Portable Potentiostat for Three-Electrode Electrochemical Sensor

This article reports a portable potentiostat based on a three-electrode electrochemical measurement system, which can be powered and communicated through the OTG interface of a smartphone. The system includes the design of the board-level potentiostat circuit, the generation of excitation in common forms required in electrochemical reactions, and the design of signal capture and analysis circuits. The potentiostat applies the positive and negative step-shaped excitations generated by the excitation generating circuit between the working electrode and the reference electrode stably. Through special excitation methods, the stripping current measured by the working electrode is consistent with that of a large electrochemical workstation. By simulating the classical three-electrode electrochemical solution environment impedance model, the constant potential error of the potentiostat was finally tested to be below 30mV through the detection circuit.

Complex Capacitance Analysis on Electrochemical Properties of Passive Film Formed on Rebar in Concrete

Reinforced concrete structures have been widely used for the social infrastructures because the rebar embedded in concrete shows high corrosion resistance due to the formation of passive film formed on the rebar. The monitoring of the conditions of the passive film formed on the rebar is important to ensure the proper maintenance and management of reinforced concrete structures. An electrochemical impedance spectroscopy (EIS) is a useful method to evaluate the corrosion state of reinforced concrete nondestructively1, 2). In the present study, the stability of passive film formed on the rebar was evaluated in the concrete simulated environment by the EIS. A saturated calcium hydroxide solution was used to simulate the environment in concrete. The chloride ion concentration was adjusted to 3.8 mmol dm-3 and 16 mmol dm-3 by adding sodium chloride to a saturated aqueous solution of calcium hydroxide. The electrochemical impedance measurement was carried out by a three electrode system. A rod electrode made of cylindrical carbon steel (SR345) that has the same composition as rebar SD345, as is often used in actual structures, was adopted as a working electrode. A saturated KCl silver / silver chloride electrode and a platinum wire were used as a reference electrode and a counter electrode respectively. The electrochemical impedance was measured every 12 hours during immersion. The 3D impedance was measured in order to investigate the time-dependent change of the thickness of the passive film. An electrochemical measurement system (HZ-7000, Hokuto Denko Corporation) was used as the measurement device. The measurement frequency range was 10 kHz to 10 mHz with 5 points per logarithmic sweep. By plotting the admittance and capacitance calculated from the impedance of carbon steel on the complex plane, the resistance and capacitance of the passive film formed on the carbon steel were evaluated. The changes of thickness of passive film formed on the carbon steel with time were discussed. References 1) J. L. Dawson et al., Proceedings of NACE Corrosion / 78, Paper No. 125 (1978). 2) Yoshinao Hoshi et al., Electrochemistry, 87, 78-83, (2019) 3) Masayuki Itagaki et al., Electrochemistry, 75, 649-655, (2007).

Effect of Particle Size of Cathode Active Material on Electrochemical Properties of Lithium-Ion Battery Investigated by In-situ EIS

An electrochemical impedance spectroscopy (EIS) has been applied to the investigation of the electrochemical properties of LIB because the time constant related to the electrode/solution interface can be discriminated in impedance spectrum. In the present study, the effect of particle size of the cathode active material on the electrochemical properties of LIB was investigated by in-situ EIS2). The in-situ EIS2) allows for the impedance measurement of the positive electrode, negative electrode, and cell of LIB simultaneously without stopping the measurement of the charge/discharge curve. A three-electrode cell was used for the impedance measurement. An active material of positive electrode was LiCoO2 (LCO) with particle size of 5 μm, 10 μm and 20 μm. The conductive additive and binder of positive electrode were acetylene black (AB) and polyvinylidene fluoride (PVDF), respectively. The positive electrode was fabricated by hand-screen printing. An Al sheet was used as the current collector. In the present study, the theoretical capacity of the positive electrode was calculated from the capacity density of LCO, whose value was defined as 1C-rate. The C-rate denotes the charge/discharge rate, and the 1 C indicates the charge/discharge rate that can fill/empty the total capacity of a battery in an hour. An active material and a current collector of negative electrode were natural spherical graphite and Cu sheet, respectively. A lithium ring was used as the reference electrode (RE), and a mixture of an ethylene carbonate (EC) and an ethyl methyl carbonate (EMC) (3:7 by volume) containing 1 M LiPF6 were used as the electrolyte. After the charge/discharge curve measurement using potentio-galvanostat (sp-50, Bio-Logic), the impedance measurement of the positive electrode during charge/discharge was measured at 1 C by in-situ EIS. The impedance measurement was carried out in the frequency range of 100 mHz to 100 kHz at 5 frequencies per decade with AC amplitude of 10 mV. An electrochemical measurement system (HZ-7000, Hokuto Denko) was used for the measurement. After the charge/discharge curve measurement at 0.3 C, the charge transfer resistance R ct was estimated from the curve fitting of the impedance spectra of the positive electrode during charge/discharge at 1 C using an equivalent circuit. It was confirmed that the R ct value decreased with increasing SOC at each particle size. Comparing the R ct values at each SOC, the R ct values at discharge were larger than that at the charge. This indicates that R ct is varied depending on the direction of current. Furthermore, the R ct values at each particle size during charge and discharge were decreased with decreasing the particle size, demonstrating the increase of the reaction surface area on the cathode active material. On the basis of these results, the diffusion distance of Li ions in the solid phase during charge/discharge was discussed.