Electrode and electrochemical measurement system

Abstract

An electrode (1) is provided with a substrate (2), a niobium layer (3), and a conductive carbon layer (4) in this order on one side in the thickness direction. The niobium layer (3) has a thickness of 5 nm or more. The electrode (1) is an electrode for electrochemical measurement. An electrochemical measurement system (10) is provided with an electrode (1).

Description

Technical Field

[0001] The present invention relates to an electrode and an electrochemical measurement system. Background Art

[0002] There is known an electrode having a substrate, a metal base layer, and a conductive carbon layer (for example, see Patent Document 1 below). In Patent Document 1, tungsten, chromium, molybdenum, and tantalum are listed as materials for the metal base layer.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: WO2021 / 193631 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] When an electrode is used as an electrode for electrochemical measurement, it is required to have excellent activity against ferrocyanide.

[0008] In addition, an electrode is required to suppress the change amount of surface resistance over a long period of time.

[0009] The present invention provides an electrode and an electrochemical measurement system that have excellent activity against ferrocyanide and can suppress the change amount of surface resistance after a long period of time.

[0010] Means for Solving the Problems

[0011] The present invention [1] includes an electrode having, in this order from one side in the thickness direction, a substrate, a niobium layer, and a conductive carbon layer, wherein the thickness of the niobium layer is 5 nm or more.

[0012] The present invention [2] includes the electrode according to [1], wherein the thickness of the niobium layer is 10 nm or more. The present invention [3] includes the electrode according to [1], wherein the thickness of the niobium layer is 20 nm or more. The present invention [4] includes the electrode according to any one of [1] to [3], wherein the ratio ([R1 - R0] / R0) of the value obtained by subtracting the surface resistance R0 from the surface resistance R1 to the surface resistance R0 is 0.10 or less, where the surface resistance R0 is the surface resistance of one side of the electrode in the thickness direction, and the surface resistance R1 is the surface resistance of the one side after the electrode is placed at 40 °C and 92% RH for 240 hours.

[0013] The present invention [5] includes the electrode according to any one of [1] to [4], wherein the substrate is a resin film.

[0014] The present invention [6] includes the electrode according to [5], which is an electrode for electrochemical measurement.

[0015] The present invention [7] includes an electrochemical measurement system, which includes the electrode described in [6].

[0016] Effects of the Invention

[0017] Due to the presence of a niobium layer between the substrate and the conductive carbon layer, the electrode of the present invention has excellent activity towards ferricyanide.

[0018] Since the thickness of the niobium layer is 5 nm or more, it is possible to suppress the change amount of the surface resistance after a long time.

[0019] The electrochemical measurement system has excellent sensitivity to ferricyanide and excellent sensitivity reliability over a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 shows a cross-sectional view of an embodiment of the electrode of the present invention.

[0021] Figure 2 is a schematic diagram of an embodiment of the electrochemical measurement system of the present invention.

[0022] Figure 3 Figure 3 A - Figure 3 B explains the conduction test after abrasion; Figure 3 A shows the method of abrading the electrode with a pencil; Figure 3 B is from Figure 3 The electrode shown in A is used to make a sample, and the method of conducting a conduction test on the sample. DETAILED DESCRIPTION OF THE INVENTION

[0023] Refer to Figure 1 To describe an embodiment of the electrode of the present invention.

[0024] 1. Electrode 1

[0025] As Figure 1 shown, the electrode 1 has a thickness. The electrode 1 extends in the plane direction. The plane direction is orthogonal to the thickness direction. The electrode 1 has a film shape or a sheet shape. There is no difference between the film and the sheet. The thickness of the electrode 1 is, for example, 2 μm or more, preferably 10 μm or more, and, for example, 1000 μm or less, preferably 500 μm or less.

[0026] In this embodiment, the electrode 1 sequentially includes a substrate 2, a niobium layer 3, and a conductive carbon layer 4 on one side facing the thickness direction.

[0027] 1.1 Substrate 2

[0028] ​​​​The base material 2 is disposed at the other end of the electrode 1 in the thickness direction. The base material 2 extends in the plane direction. The base material 2 has a film shape or a sheet shape. Examples of the material of the base material 2 include resin, ceramic, and metal. From the viewpoint of ensuring the flexibility of the base material 2, resin is preferably cited as the material of the base material 2. In other words, the base material 2 is preferably a resin film. It should be noted that when the material is ceramic, the base material 2 is a ceramic foil. When the material is metal, the base material 2 is a metal foil. The base material 2 has flexibility.

[0029] Examples of the resin include polyester resin, acetate resin, polyethersulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, (meth)acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl alcohol resin, polyarylate resin, and polyphenylene sulfide resin. The resins can be used alone or in combination. As the resin, polyester resin is preferably cited, and polyethylene terephthalate is preferably cited. The thickness of the base material 2 is, for example, 1.9 μm or more, preferably 9 μm or more, and, for example, 999 μm or less, preferably 499 μm or less.

[0030] 1.2 Niobium layer 3

[0031] The niobium layer 3 is disposed on one surface of the base material 2 in the thickness direction. The niobium layer 3 is in contact with one surface of the base material 2 in the thickness direction. The niobium layer 3 extends in the plane direction. The niobium layer 3 is a base layer. The base layer assists the conductivity of the conductive carbon layer 4.

[0032] The thickness of the niobium layer 3 is 5 nm or more. If the thickness of the niobium layer 3 is less than 5 nm, the activity of the ferrocyanide decreases.

[0033] The thickness of the niobium layer 3 is preferably 8 nm or more, more preferably 10 nm or more, further preferably 15 nm or more, particularly preferably 20 nm or more, further 25 nm or more, further preferably 45 nm or more, and particularly preferably 60 nm or more. If the thickness of the niobium layer 3 is above the above lower limit, the abrasion resistance is excellent, the sensitivity reliability over a long time is excellent, and the surface resistance can be reduced. The abrasion resistance includes the property of ensuring the conductivity of the conductive carbon layer 4 even when rubbed by a hard foreign object.

[0034] There is no limitation on the upper limit of the thickness of the niobium layer 3. The upper limit of the thickness of the niobium layer 3 is, for example, 1,000 nm, further 500 nm, and further 100 nm. The thickness of the niobium layer 3 is obtained as described below together with the conductive carbon layer 4.

[0035] The method for measuring the thickness of the niobium layer 3 and the thickness of the conductive carbon layer 4 is as follows. Specifically, based on the principle of X-ray reflectivity, using a powder X-ray diffractometer (manufactured by Rigaku Corporation, "RINT-2200"), the X-ray reflectivity is measured under the following <measurement conditions>, and the obtained measurement data is analyzed using analysis software (manufactured by Rigaku Corporation, "GXRR3"), thereby calculating the thickness of the niobium layer 3 and the thickness of the conductive carbon layer 4. For the analysis, under the following <analysis conditions>, a three-layer model of the substrate 2, the niobium layer 3, and the conductive carbon layer 4 is adopted, and the target thickness and density of the niobium layer 3 of 8.57 g / cm 3 are input as initial values. Additionally, the target thickness and density of the conductive carbon layer 4 of 1.95 g / cm 3 are input as initial values. Then, by performing the least-squares fitting with the measured values, the thicknesses of the niobium layer 3 and the conductive carbon layer 4 are calculated respectively.

[0036] <Measurement conditions>

[0037] Measuring device: Powder X-ray diffractometer (manufactured by Rigaku Corporation, "RINT-2000") Light source: Cu-Kα ray (wavelength: )、40 kV、40 mA

[0038] Optical system: Parallel beam optical system

[0039] Divergence slit: 0.05 mm

[0040] Receiving slit: 0.05 mm

[0041] Monochromatization·Parallelization: Use a multilayer Goebel mirror

[0042] Measurement mode: θ / 2θ scanning mode

[0043] Measurement range (2θ): 0.3 to 2.0°

[0044] <Analysis conditions>

[0045] Analysis software: Manufactured by Rigaku Corporation, "GXRR3"

[0046] Analysis method: Least-squares fitting

[0047] Analysis range (2θ): 2θ = 0.3 to 2.0°

[0048] 1.3 Conductive carbon layer 4

[0049] The conductive carbon layer 4 is disposed at one end of the electrode 1 in the thickness direction. The conductive carbon layer 4 is disposed on one surface of the niobium layer 3 in the thickness direction. The conductive carbon layer 4 is in contact with one surface of the niobium layer 3 in the thickness direction. The conductive carbon layer 4 is disposed on the side opposite to the substrate 2 with respect to the niobium layer 3 in the thickness direction.

[0050] The conductive carbon layer 4 may also include, for example, sp 2 bonds and sp 3 bonds. When the conductive carbon layer 4 includes sp 2 bonds and sp 3 bonds, the conductive carbon layer 4 has a graphite-type structure and a diamond structure. The conductive carbon layer 4 may contain, for example, oxygen in addition to carbon. In addition, the conductive carbon layer 4 allows a small amount of inevitable impurities other than oxygen to be mixed in.

[0051] The thickness of the conductive carbon layer 4 is, for example, 0.1 nm or more, preferably 0.2 nm or more, and further, 100 nm or less, preferably 50 nm or less.

[0052] 1.4 Physical properties of the electrode 1

[0053] The ratio ([R1 - R0] / R0) of the value obtained by subtracting the surface resistance R0 from the surface resistance R1 to the surface resistance R0 is, for example, 2.00 or less, preferably 1.0 or less, more preferably 0.50 or less, further preferably 0.20 or less, further 0.10 or less, 0.04 or less, 0.02 or less, 0.01 or less, less than 0.01, and, for example, -0.10 or more, preferably -0.05 or more, where the surface resistance R0 is the surface resistance of one surface of the electrode 1 in the thickness direction, and the surface resistance R1 is the surface resistance of one surface of the electrode 1 after being placed at 40 °C and 92% RH for 240 hours. If the above ratio ([R1 - R0] / R0) is below the above upper limit, the sensitivity reliability over a long period is excellent. The surface resistances R0 and R1 are obtained as follows. The electrode 1 is cut into a size of 50 × 50 mm, and using NC-80LINE manufactured by NAPSON Corporation, the absolute value of the resistance is measured by the eddy current method. Scanning is performed using a non-contact measurement probe unit, and the average value of the sheet resistance after removing the data of the two ends of 10 mm is used as the surface resistances R0 and R1.

[0054] 1.5 Manufacturing method of the electrode 1

[0055] In this method, first, the substrate 2 is prepared.

[0056] In this method, next, a niobium layer 3 is formed on one side of the substrate 2 in the thickness direction. The method for forming the niobium layer 3 is not particularly limited. As the method for forming the niobium layer 3, for example, a dry method and a wet method can be cited. As the method for forming the niobium layer 3, a dry method is preferably cited. As the dry method, for example, a PVD method (physical vapor deposition method), a CVD method (chemical vapor deposition method) can be cited, and a PVD method is preferably cited. As the PVD method, for example, sputtering, vacuum evaporation, laser evaporation, and ion plating can be cited. As the PVD, sputtering is preferably cited. The target in sputtering is, for example, niobium. Electric power can be applied to the target. The target has, for example, a plate shape. The electric power is appropriately set corresponding to the thickness of the niobium layer 3. As the sputtering gas, for example, an inert gas can be cited. As the inert gas, for example, Ar can be cited. The pressure in sputtering is, for example, 0.01 Pa or more and 5 Pa or less. The film formation temperature is, for example, -10 °C or more, preferably 20 °C or more, and for example, 200 °C or less, preferably 150 °C or less.

[0057] In this method, then, a conductive carbon layer 4 is formed on one side of the niobium layer 3 in the thickness direction. The method for forming the conductive carbon layer 4 is not particularly limited. The conductive carbon layer 4 can be cited as the same method as the method for forming the niobium layer 3, and sputtering is preferably cited. The target in sputtering is, for example, sintered carbon.

[0058] 1.6 Use

[0059] The use of the electrode 1 is not limited. The electrode 1 is preferably an electrode for electrochemical measurement for carrying out an electrochemical measurement method. Specifically, it can be used as a working electrode (working pole) for carrying out cyclic voltammetry (CV).

[0060] As the object of electrochemical measurement (measurement object), for example, ferricyanide can be cited. As ferricyanide, for example, potassium ferricyanide and sodium ferricyanide can be cited.

[0061] 1.7 Electrochemical Measurement System

[0062] Reference Figure 2 An embodiment of the electrochemical measurement system of the present invention will be described. The electrochemical measurement system 10 includes a working electrode 11, a reference electrode 12, a counter electrode 13, a voltage regulator 14, and an ammeter (not shown).

[0063] The working electrode 11 includes the above-mentioned electrode 1. In other words, the electrochemical measurement system 10 includes the above-mentioned electrode 1. That is, the electrode 1 is used for electrochemical measurement.

[0064] As the reference electrode 12, for example, a silver / silver chloride electrode, a saturated calomel electrode, and a standard hydrogen electrode can be cited.

[0065] As the counter electrode 13, for example, a platinum electrode, a gold electrode, and a nickel electrode can be cited.

[0066] The working electrode 11, reference electrode 12, and counter electrode 13 described above can be immersed in the target liquid 15. The target liquid 15 contains the above-mentioned measurement target. For example, when performing CV, a potential applied to the working electrode 11 (carbon electrode 1) is applied and scanned.

[0067] 1.8 Effects of an Embodiment

[0068] As Figure 1 shown, the electrode 1 has a niobium layer 3 between the substrate 2 and the conductive carbon layer 4. Therefore, the electrode 1 is excellent in activity towards ferricyanide.

[0069] Since the thickness of the niobium layer 3 is 5 nm or more, the change amount of the surface resistance after a long time can be suppressed.

[0070] If the thickness of the niobium layer 3 is 10 nm or more, the abrasion resistance is excellent, the sensitivity reliability over a long time is excellent, and the surface resistance can be reduced. If the thickness of the niobium layer 3 is 10 nm or more, the surface resistance can be significantly reduced in particular.

[0071] If the thickness of the niobium layer 3 is 20 nm or more, the abrasion resistance is excellent, the sensitivity reliability over a long time is excellent, and the surface resistance can be reduced.

[0072] As Figure 2 shown, since the electrochemical measurement system 10 includes the above-mentioned electrode 1 (see Figure 1 ), it is excellent in sensitivity to ferricyanide and excellent in sensitivity reliability over a long time.

[0073] 2. Variation

[0074] Although not shown, the electrode 1 may further have a hard coat. The hard coat is disposed, for example, on the other side of the substrate 2 in the thickness direction.

[0075] Examples

[0076] Examples and comparative examples are shown below to further specifically illustrate the present invention. It should be noted that the present invention is not limited by any of the examples and comparative examples. In addition, the specific numerical values such as the mixing ratio (content ratio), physical property values, and parameters used in the following description can be replaced with the upper limit values (defined as "below", "less than") or lower limit values (defined as "above", "greater than") of the corresponding mixing ratios (content ratios), physical property values, and parameters described in the above "Specific Embodiments".

[0077] Example 1

[0078] First, a substrate 2 made of polyethylene terephthalate with a thickness of 100 μm was prepared.

[0079] Next, a niobium layer 3 is formed on one side of the substrate 2 in the thickness direction by sputtering. The thickness of the niobium layer 3 is 5 nm. The sputtering conditions are described below.

[0080] Target material: Niobium (Nb)

[0081] Sputtering gas: Ar

[0082] Sputtering pressure: 0.2 Pa

[0083] Target material power: 0.4 W / cm 2

[0084] Film formation temperature: 40 °C

[0085] Then, a conductive carbon layer 4 is formed on one side of the niobium layer 3 in the thickness direction by sputtering. The thickness of the conductive carbon layer 4 is 10 nm. The sputtering conditions are described below.

[0086] Sputtering gas: Ar

[0087] Sputtering pressure: 0.2 Pa

[0088] Target material power: 3 W / cm 2

[0089] Film formation temperature: 40 °C

[0090] Thus, the electrode 1 is manufactured.

[0091] Examples 2 to 7 and Comparative Example 3

[0092] The same treatment as in Example 1 is carried out to obtain the electrode 1. Among them, the thickness of the niobium layer 3 is changed according to the description in Table 1.

[0093] Comparative Example 1 and Comparative Example 2

[0094] The same treatment as in Example 1 is carried out to obtain the electrode 1. Among them, according to the description in Table 1, a titanium layer is formed instead of the niobium layer 3, and the thickness of the titanium layer is also changed.

[0095] [Evaluation]

[0096] 1.1 Activity against potassium ferricyanide

[0097] For each of the electrodes 1 of Examples 1 to Comparative Example 3, the activity against potassium ferricyanide was evaluated. The results are shown in Table 1.

[0098] Specifically, an insulating tape with holes having a diameter of 2 mm was pasted on one side of the conductive carbon layer 4 to fabricate a sample electrode with a known electrode area. This sample electrode was used as the working electrode, and cyclic voltammetry (CV) was performed. Specifically, the sample electrode was immersed in a 1 M KCl aqueous solution. In addition, 1 mM of [Fe(CN)6] 4- (ferrocyanide ion) was added to the aqueous solution. In the CV measurement, the potential was scanned starting from 0 V, and the potential was scanned from the positive direction to the negative direction in the range of -0.1 to 0.5 V. The scanning rate of the potential was 0.1 V / s. The CV measurement was carried out at 23 °C. The number of CV measurements was set to 3. The average value of the three ΔEp values in the CV measurement was taken as the initial ΔEp. The ΔEp at this time was taken as the activity of Electrode 1 towards potassium ferricyanide.

[0099] 1.2 Surface resistance R0

[0100] For Electrode 1 of each of Examples 1 to Comparative Example 3, the surface resistance R0 was determined. The results are shown in Table 1.

[0101] Specifically, the surface resistance R0 of one side of Electrode 1 in the thickness direction was measured. Regarding the surface resistance R0, the electrodes 1 of the examples and comparative examples were each cut into a size of 50 × 50 mm, and using NC-80LINE manufactured by NAPSON Corporation, the absolute value of the resistance was measured by the eddy current method.

[0102] Scanning was performed using a non-contact measurement probe unit, and the average value of the sheet resistance after removing the data of the two ends of 10 mm was taken as the surface resistance.

[0103] 1.3 Ratio (ratio of the change in surface resistance over a long time)

[0104] For Electrode 1 of each of Examples 1 to Comparative Example 3, the ratio of the change in surface resistance over a long time was determined. The results are shown in Table 1.

[0105] (1) First, the surface resistance R0 of the above "1.2 Surface resistance R0" was used as the reference for the change in surface resistance.

[0106] (2) Next, Electrode 1 was placed at 40 °C and 92% RH for 240 hours. Then, the surface resistance R1 of one side of the placed Electrode 1 was measured. The surface resistance R1 was determined in the same manner as the measurement of the surface resistance R0.

[0107] (3) R0 and R1 were respectively substituted into the following formula to calculate the ratio (ratio of the change in surface resistance over a long time).

[0108] Ratio = ([R1 - R0] / R0)

[0109] 1.4 Conduction Test after Pencil Scratch

[0110] As shown in Figure 3 A, on one side of the electrode 1 in each of Examples 1 to 7, a pencil was slid and rubbed in one direction. The conditions for the sliding friction are described below.

[0111] Load: 500 g

[0112] Sliding friction speed: 1 mm / sec

[0113] Sliding friction length: 10 mm

[0114] Pencil hardness: F, H, 2H, 3H

[0115] After the sliding friction, as shown in Figure 3 B, the electrode 1 was machined in shape in such a way as to include the middle part of the sliding friction part in the sliding friction direction (equivalent to one direction), to obtain Sample 1S. The sliding friction part 1R continuously exists at one end, the middle part, and the other end of Sample 1S in the sliding friction direction. Thus, in the direction orthogonal to the sliding friction direction and the thickness direction, two non-sliding friction regions 1A, 1B are separated by the sliding friction part 1R. That is, the electrical path between the two non-sliding friction regions 1A, 1B passes through (across) the sliding friction part 1R.

[0116] In each case of pencil hardness F, H, 2H, 3H, the conduction between the two non-sliding friction regions 1A, 1B was confirmed using the tester T.

[0117] Five tests were conducted for each of the pencil hardnesses F, H, 2H, 3H. The conduction after the pencil sliding friction was evaluated as follows.

[0118] ○: Three or more, conduction.

[0119] △: One or two, conduction.

[0120] ×: Zero, conduction.

[0121] The results are shown in Table 2.

[0122] [Table 1]

[0123] Table 1

[0124]

[0125] [Table 2]

[0126] Table 2

[0127]

[0128] Description of Reference Numerals

[0129] 1 Electrode

[0130] 2 Substrate

[0131] 3 Niobium layer

[0132] 4 Conductive carbon layer

[0133] 10 Electrochemical measurement system

[0134] Surface resistance of one side of the electrode before R0 placement

[0135] R1 Surface resistance of one side of the electrode after the electrode is placed under the conditions of 40 °C and 92% RH for 240 hours

[0136] R0 Surface resistance

[0137] It should be noted that the above invention is provided as an exemplary embodiment of the present invention, but this is only an example and is not to be construed in a limiting sense. Variations of the present invention that are obvious to those skilled in the art are also included within the scope of the foregoing claims.

[0138] Industrial applicability

[0139] The electrode and the electrochemical measurement system of the present invention can be suitably used in various fields of electrochemical measurement.

Claims

1. An electrode having, in order on one side in the thickness direction, a substrate, a niobium layer, and a conductive carbon layer, The thickness of the niobium layer is 5 nm or more.

2. The electrode according to claim 1, wherein, The thickness of the niobium layer is 10 nm or more.

3. The electrode according to claim 1, wherein, The thickness of the niobium layer is 20 nm or more.

4. The electrode according to claim 3, wherein, The ratio ([R1 - R0] / R0) of the value obtained by subtracting the surface resistance R0 from the surface resistance R1 to the surface resistance R0 is 0.10 or less, where the surface resistance R0 is the surface resistance of one side of the electrode in the thickness direction, and the surface resistance R1 is the surface resistance of the one side after the electrode is placed under the conditions of 40 °C and 92% RH for 240 hours.

5. The electrode according to any one of claims 1 to 4, wherein, The substrate is a resin film.

6. The electrode according to claim 5, which is an electrode for electrochemical measurement.

7. An electrochemical measurement system comprising the electrode according to claim 6.

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