Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
  • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
  • G01N27/28—Electrolytic cell components
  • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
  • G01N27/308—Electrodes, e.g. test electrodes; Half-cells at least partially made of carbon
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B15/00—Layered products comprising a layer of metal
  • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B15/00—Layered products comprising a layer of metal
  • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B9/00—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B9/00—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00
  • B32B9/04—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00 comprising such particular substance as the main or only constituent of a layer, which is next to another layer of the same or of a different material

Definitions

• the present invention relates to an electrode and an electrochemical measurement system.
• Patent Document 1 An electrode comprising a substrate, a metal underlayer, and a conductive carbon layer is known (see, for example, Patent Document 1 below).
• Patent Document 1 lists tungsten, chromium, molybdenum, and tantalum as materials for the metal underlayer.
• the electrode is used for electrochemical measurements and is required to have excellent activity against ferricyanide compounds.
• the electrodes are required to suppress changes in surface resistance over time.
• the present invention provides an electrode and an electrochemical measurement system that have excellent activity toward ferricyanide compounds and can suppress the amount of change in surface resistance after a long period of time.
• the present invention [1] includes an electrode having a substrate, a niobium layer, and a conductive carbon layer, arranged in that order toward one side in the thickness direction, and the thickness of the niobium layer is 5 nm or more.
• the present invention [2] includes the electrode described in [1], in which the thickness of the niobium layer is 10 nm or more.
• the present invention [3] includes the electrode described in [1], in which the thickness of the niobium layer is 20 nm or more.
• the present invention [4] includes an electrode according to any one of [1] to [3], in which the ratio ([R1-R0]/R0) of the surface resistance R1 of one side of the electrode minus the surface resistance R0 of the electrode in the thickness direction after the electrode is left at 40°C and 92% RH for 240 hours is 0.10 or less.
• the present invention [6] includes the electrode described in [5], which is an electrode for electrochemical measurements.
• the present invention [7] includes an electrochemical measurement system having the electrode described in [6].
• the electrode of the present invention has a niobium layer between the substrate and the conductive carbon layer, and therefore has excellent activity toward ferricyanide compounds.
• the thickness of the niobium layer is 5 nm or more, so the amount of change in surface resistance after a long period of time can be suppressed.
• the electrochemical measurement system has excellent sensitivity to ferricyanide compounds and excellent long-term sensitivity reliability.
• FIG. 1 shows a cross-sectional view of one embodiment of an electrode of the present invention.
• FIG. 1 is a schematic diagram of an embodiment of an electrochemical measurement system of the present invention.
• 3A-3B illustrate the continuity test after scratching.
• Fig. 3A shows an embodiment in which an electrode is scratched with a pencil.
• Fig. 3B shows an embodiment in which a sample is made from the electrode shown in Fig. 3A and the sample is subjected to a continuity test.
• Electrode 1 As shown in FIG. 1, the electrode 1 has a thickness. The electrode 1 extends in a planar direction. The planar direction is perpendicular to the thickness direction. The electrode 1 has a film or sheet shape. The film and the sheet are The thickness of the electrode 1 is, for example, 2 ⁇ m or more, preferably 10 ⁇ m or more, and for example, 1000 ⁇ m or less, preferably 500 ⁇ m or less. In this embodiment, the electrode 1 includes a substrate 2, a niobium layer 3, and a conductive carbon layer 4 in this order toward one side in the thickness direction.
• the substrate 2 is disposed at the other end of the electrode 1 in the thickness direction.
• the substrate 2 extends in the planar direction.
• the substrate 2 has a film or sheet shape.
• materials for the substrate 2 include resin, ceramics, and metal.
• a preferable material for the substrate 2 is resin, from the viewpoint of ensuring the flexibility of the substrate 2.
• the substrate 2 is preferably a resin film. If the material is ceramic, the substrate 2 is a ceramic foil. If the material is metal, the substrate 2 is a metal foil.
• the substrate 2 has flexibility.
• the resin examples 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 resin can be used alone or in combination.
• Examples of the resin include preferably polyester resin, and preferably polyethylene terephthalate.
• the thickness of the substrate 2 is, for example, 1.9 ⁇ m or more, preferably 9 ⁇ m or more, and, for example, 999 ⁇ m or less, preferably 499 ⁇ m or less.
• Niobium layer 3 The niobium layer 3 is disposed on one surface of the substrate 2 in the thickness direction. The niobium layer 3 contacts one surface of the substrate 2 in the thickness direction. The niobium layer 3 extends in the planar direction. The niobium layer 3 is an underlayer. The underlayer assists the conductivity of the conductive carbon layer 4.
• 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, its activity against the ferricyanide compound decreases.
• the thickness of the niobium layer 3 is preferably 8 nm or more, more preferably 10 nm or more, even more preferably 15 nm or more, particularly preferably 20 nm or more, even more preferably 25 nm or more, even more preferably 45 nm or more, and particularly preferably 60 nm or more. If the thickness of the niobium layer 3 is equal to or greater than the above-mentioned lower limit, it has excellent scratch resistance, excellent long-term sensitivity reliability, and can reduce surface resistance. Scratch resistance includes the property of being able to ensure the conductivity of the conductive carbon layer 4 even when it is rubbed by a hard foreign object.
• the upper limit of the thickness of the niobium layer 3 is not limited.
• the upper limit of the thickness of the niobium layer 3 is, for example, 1,000 nm, further 500 nm, or further 100 nm.
• the thickness of the niobium layer 3, together with the conductive carbon layer 4, is determined, for example, as follows.
• the method for measuring the thickness of the niobium layer 3 and the conductive carbon layer 4 is described below.
• the measurement principle is X-ray reflectivity
• a powder X-ray diffractometer (Rigaku Corporation, "RINT-2200") is used to measure X-ray reflectivity under the following ⁇ measurement conditions>.
• the obtained measurement data is analyzed with analysis software (Rigaku Corporation, "GXRR3") to calculate the thickness of the niobium layer 3 and the thickness of the conductive carbon layer 4.
• a three-layer model consisting of a substrate 2, a niobium layer 3, and a conductive carbon layer 4 is adopted under the following ⁇ Analysis Conditions>, and the target thickness and density of the niobium layer 3, 8.57 g/ cm3 , are input as initial values, and the target thickness and density of the conductive carbon layer 4, 1.95 g/ cm3 , are input as initial values. Thereafter, the thicknesses of the niobium layer 3 and the conductive carbon layer 4 are each calculated by performing least squares fitting with the actual measured values.
• Measurement equipment Powder X-ray diffraction equipment (Rigaku Corporation, "RINT-2000")
• Light source Cu-K ⁇ radiation (wavelength: 1,5418 ⁇ ), 40 kV, 40 mA
• Optical system Parallel beam optical system Divergence slit: 0.05 mm Receiving slit: 0.05 mm
• Monochromatization and parallelization Uses multi-layer Goebel mirrors Measurement mode: ⁇ /2 ⁇ scan mode Measurement range (2 ⁇ ): 0.3 to 2.0°
• Conductive carbon layer 4 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 opposite side of the substrate 2 with respect to the niobium layer 3 in the thickness direction.
• the conductive carbon layer 4 may have, for example, sp2 bonds and sp3 bonds. When the conductive carbon layer 4 has sp2 bonds and sp3 bonds, the conductive carbon layer 4 has a graphite structure and a diamond structure.
• the conductive carbon layer 4 may contain, for example, oxygen in addition to carbon. Furthermore, the conductive carbon layer 4 is allowed to contain a small amount of inevitable impurities other than oxygen.
• the thickness of the conductive carbon layer 4 is, for example, 0.1 nm or more, preferably 0.2 nm or more, and 100 nm or less, preferably 50 nm or less.
• the ratio ([R1-R0]/R0) of the surface resistance R1 of one side of electrode 1 after leaving electrode 1 at 40°C and 92% RH for 240 hours minus the surface resistance R0 of one side of electrode 1 in the thickness direction to the surface resistance R0 of one side of electrode 1 is, for example, 2.00 or less, preferably 1.0 or less, more preferably 0.50 or less, even more 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 is, for example, -0.10 or more, preferably -0.05 or more. If the above ratio ([R1-R0]/R0) is equal to or less than the above upper limit, the long-term sensitivity reliability is excellent.
• the surface resistances R0 and R1 are calculated as follows.
• Cut electrode 1 to a size of 50 x 50 mm, and measure the absolute resistance value by eddy current measurement using a NAPSON NC-80LINE. Sweep the non-contact measurement probe unit, and use the average sheet resistance value excluding data for 10 mm from both ends as the surface resistance R0, R1.
• the niobium layer 3 is then formed on one side of the substrate 2 in the thickness direction.
• the method of forming the niobium layer 3 is not particularly limited. Examples of the method of forming the niobium layer 3 include a dry method and a wet method. A preferred method of forming the niobium layer 3 is a dry method. Examples of the dry method include a PVD method (physical vapor deposition method) and a CVD method (chemical vapor deposition method), and a preferred method is a PVD method. Examples of the PVD method include sputtering, vacuum deposition, laser deposition, and ion plating. A preferred example of the PVD method is sputtering.
• the target in the sputtering is, for example, niobium.
• the target can be applied with electric power.
• the target has, for example, a plate shape.
• the electric power is appropriately set according to the thickness of the niobium layer 3.
• the sputtering gas include an inert gas.
• the inert gas include Ar.
• the pressure in the sputtering is, for example, 0.01 Pa or more and 5 Pa or less.
• the film formation temperature is, for example, -10°C or higher, preferably 20°C or higher, and, for example, 200°C or lower, preferably 150°C or lower.
• the conductive carbon layer 4 is then 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 formed by the same method as the method for forming the niobium layer 3, preferably by sputtering.
• the target for sputtering is, for example, sintered carbon.
• the electrode 1 can be preferably used as an electrode for electrochemical measurement for performing an electrochemical measurement method, specifically, as a working electrode for performing cyclic voltammetry (CV).
• CV cyclic voltammetry
• Examples of the subject of electrochemical measurement include ferricyanide compounds.
• Examples of ferricyanide compounds include potassium ferricyanide and sodium ferricyanide.
• the electrochemical measurement system 10 includes a working electrode 11, a reference electrode 12, a counter electrode 13, a potentiostat 14, and an ammeter (not shown).
• the working electrode 11 includes the electrode 1 described above.
• the electrochemical measurement system 10 includes the electrode 1 described above.
• the electrode 1 is used for electrochemical measurement.
• Examples of the reference electrode 12 include a silver/silver chloride electrode, a saturated calomel electrode, and a standard hydrogen electrode.
• Examples of the counter electrode 13 include a platinum electrode, a gold electrode, and a nickel electrode.
• 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 is applied to the working electrode 11 (carbon electrode 1) and this is scanned.
• the electrode 1 includes a niobium layer 3 between a substrate 2 and a conductive carbon layer 4. Therefore, the electrode 1 has excellent activity with respect to ferricyanide compounds.
• the thickness of the niobium layer 3 is 5 nm or more, so the amount of change in surface resistance after a long period of time can be suppressed.
• the thickness of the niobium layer 3 is 10 nm or more, it has excellent scratch resistance, excellent long-term sensitivity reliability, and can reduce surface resistance. If the thickness of the niobium layer 3 is 10 nm or more, it can significantly reduce surface resistance.
• the thickness of the niobium layer 3 is 20 nm or more, it has excellent scratch resistance, excellent long-term sensitivity reliability, and can reduce surface resistance.
• the electrochemical measurement system 10 includes the above-mentioned electrode 1 (see FIG. 1), and therefore has excellent sensitivity to ferricyanide compounds and excellent sensitivity reliability over a long period of time.
• the electrode 1 may further include a hard coat layer.
• the hard coat layer is disposed, for example, on the other surface of the substrate 2 in the thickness direction.
• Example 1 First, a substrate 2 made of polyethylene terephthalate having a thickness of 100 ⁇ m was prepared.
• a niobium layer 3 was formed on one side of the substrate 2 in the thickness direction by sputtering.
• the thickness of the niobium layer 3 was 5 nm. The sputtering conditions are described below.
• Target material niobium (Nb) Sputtering gas: Ar Sputtering pressure: 0.2 Pa Target power: 0.4 W/ cm2 Film formation temperature: 40° C.
• a conductive carbon layer 4 was formed on one side of the niobium layer 3 in the thickness direction by sputtering.
• the thickness of the conductive carbon layer 4 was 10 nm. The sputtering conditions are described below.
• Sputtering gas Ar Sputtering pressure: 0.2 Pa
• Target power 3 W/ cm2
• Film formation temperature 40° C.
• Example 2 to 7 and Comparative Example 3 The electrode 1 was obtained by the same treatment as in Example 1. However, the thickness of the niobium layer 3 was changed according to the description in Table 1.
• Comparative Example 1 and Comparative Example 2 An electrode 1 was obtained by the same treatment as in Example 1. However, according to the description in Table 1, a titanium layer was formed instead of the niobium layer 3, and the thickness of the titanium layer was also changed.
• an insulating tape having a hole of 2 mm in diameter was attached to one side of the conductive carbon layer 4 to prepare a sample electrode with a known electrode area.
• Cyclic voltammetry (CV) was performed using this sample electrode as a working electrode. Specifically, the sample electrode was immersed in a 1M KCl aqueous solution. In addition, 1 mM of [Fe(CN) 6 ] 4- (ferricyanide ion) was added to the aqueous solution as an electrode active material.
• the potential sweep was started from 0 V, and the potential was swept from positive to negative in the range of -0.1 to 0.5 V. The potential sweep speed was 0.1 V/s.
• the CV measurement was performed at 23°C. The number of CV measurements was 3. The average value of the ⁇ Ep values obtained three times in the CV measurement was obtained as the initial ⁇ Ep. The ⁇ Ep at this time was taken as the activity of the electrode 1 with respect to potassium ferricyanide.
• the surface resistance R0 of one surface of the electrode 1 in the thickness direction was measured.
• the electrode 1 of each of the examples and comparative examples was cut to a size of 50 x 50 mm, and the absolute resistance value was measured by eddy current measurement using an NC-80LINE manufactured by NAPSON Corporation.
• the non-contact measuring probe unit was swept, and the average value of the sheet resistance values excluding the data for 10 mm at both ends was taken as the surface resistance.
• Ratio ratio of surface resistance change over time
• the ratio of the amount of change in surface resistance over time was determined for each of the electrodes 1 of Example 1 to Comparative Example 3. The results are shown in Table 1.
• the electrode 1 was contoured to include the middle part of the rubbing portion in the rubbing direction (corresponding to one direction), to obtain sample 1S.
• rubbing portion 1R exists continuously at one end, middle part, and other end of sample 1S in the rubbing direction.
• two non-rubbing regions 1A, 1B are separated by rubbing portion 1R in a direction perpendicular to the rubbing direction and thickness direction.
• the electrical path between the two non-rubbing regions 1A, 1B passes through (crosses) rubbing portion 1R.
• the conduction between the two non-friction areas 1A and 1B was confirmed using tester T for each of the pencil hardnesses F, H, 2H, and 3H.
• ⁇ Three or more were conductive. ⁇ : One or two were conductive. ⁇ : 0 pieces, conductive.
• Electrode 2 Substrate 3 Niobium layer 4 Conductive carbon layer 10
• Electrochemical measurement system R0 Surface resistance of one side of the electrode before standing
• R1 Surface resistance of one side of the electrode after the electrode is left standing at 40° C. and 92% RH for 240 hours
• the electrode and electrochemical measurement system of the present invention can be suitably used in various electrochemical measurement fields.

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• 2023
  • 2023-11-13 EP EP23894464.9A patent/EP4624914A1/en active Pending
  • 2023-11-13 CN CN202380078462.2A patent/CN120188035A/zh active Pending
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