JP2009250824A - Electrochemical infrared spectrometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical infrared spectrometer capable of performing on-the-spot measurement of higher sensitivity in a high sensitivity infrared reflection absorption method. <P>SOLUTION: The electrochemical infrared spectrometer is provided with an acting electrode, the counter electrode forming a pair along with the acting electrode, a reference electrode for prescribing the potential of the acting electrode and a window material on which infrared rays are thrown and constituted so that an electrolyte is present in the gap between the acting electrode and the window material, the infrared rays straightly advanced from the window material are incident on the electrolyte without being totally reflected to arrive at the surface coming into contact with the electrolyte of the acting electrode and reflected by the surface of the acting electrode to arrive a detector to perform the on-the-spot measurement of the intensity of the reflected rays of the infrared rays from the surface of the acting electrode. The surface coming into contact with the electrolyte of the window material is not parallel to the surface coming into contact with the electrolyte of the acting electrode. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrochemical infrared spectrometer capable of measuring an electrode surface in situ.

In-situ measurement of electrode surface reaction by infrared spectroscopy enables the elucidation of the electrode reaction mechanism by detecting and identifying the chemical species present on or near the electrode surface. It is expected as a technology that greatly contributes to

  An example of a method for measuring the electrode surface reaction in situ by infrared spectroscopy is the total reflection absorption measurement (ATR). In the total reflection absorption measurement method, a prism and a metal thin film are brought into close contact with each other, and the reflection of light (evanescent wave) that leaks slightly from the prism through the metal thin film into the electrolyte is measured. In the total reflection absorption measurement method, infrared light does not pass through the electrolytic solution layer, so that absorption of infrared light by the electrolytic solution is small and the electrolytic solution layer can be thickened.

  Patent Document 1 discloses a technique for suppressing absorption of infrared light by the prism itself by using a total reflection absorption measurement method that has a dimension in which the maximum optical path length of infrared light in the prism is 10 mm or less. Yes.

  In the measurement using a total reflection prism, a Kretschmann arrangement in which a metal thin film is deposited on the prism and a sample is introduced thereon, and the sample is sandwiched in a minute space between the total reflection prism and the metal plate or metal thin film. Two main types of arrangement methods of Otto arrangement are well known. In the Kletzmann arrangement, when light is incident on the metal fine particles forming the metal thin film, the plasma vibration of the metal fine particles is excited and a local electric field is formed in the vicinity of the fine particles. In the Otto arrangement, when the total reflection prism-metal thin film is considered as one cavity, total reflection is repeated between the prism and the metal, and the interference electric field is excited by confining light in the cavity. By this localized electric field or interference electric field, it is possible to increase infrared absorption and improve detection sensitivity.

  In Patent Document 2, both a local electric field and an interference electric field are generated by providing a net-like metal or a grooved metal on the surface of the total reflection prism so that a viscous or liquid sample can be supported in the metal. Discloses a technique for further increasing the infrared absorption of a sample in contact with the substrate.

JP 2007-78487 A Japanese Patent Laid-Open No. 7-229829

  However, in the total reflection absorption measurement method used in Patent Documents 1 and 2, it is difficult to obtain accurate information because the interface between the metal thin film and the electrolytic solution is observed with infrared rays transmitted through the metal thin film. In addition, since a change in total reflection due to the evanescent wave that slightly leaks into the electrolyte is detected, high-sensitivity measurement cannot be expected.

Such problems of the total reflection absorption measurement method are solved by a highly sensitive infrared absorption reflection method (IRAS). In the high-sensitivity infrared absorption reflection method, infrared light is incident and reflected on the interface between the electrode and the electrolytic solution, and the intensity of the reflected light is measured to observe the electrode surface.
An object of the present invention is to provide an electrochemical infrared spectrometer capable of performing in-situ measurement with higher sensitivity in the high-sensitivity infrared absorption reflection method.

  The electrochemical infrared spectroscopic device of the present invention has a working electrode, a counter electrode paired with the working electrode, a reference electrode for regulating the potential of the working electrode, and a window material into which infrared light is incident. In addition, an electrolyte exists in the gap between the working electrode and the window material, and infrared light traveling straight from the window material enters the electrolyte without being totally reflected, and comes into contact with the electrolyte of the working electrode An electrochemical infrared spectroscopic apparatus that measures the reflected light intensity of infrared light from the electrode surface in situ by reaching the electrode surface, reflecting on the electrode surface, and reaching the detector, wherein the window material The surface of the working electrode in contact with the electrolytic solution and the surface of the working electrode in contact with the electrolytic solution are not parallel.

  In the electrochemical infrared spectroscopic device having such a configuration, since the surface of the window material that contacts the electrolyte solution and the electrode surface of the working electrode that contacts the electrolyte solution are not parallel, the window material advances straight from the window material, The direction of infrared light that reaches the electrode surface without being totally reflected and is reflected by the electrode surface is incident on the window material, and the direction of infrared light that is totally reflected on the surface of the window material that is in contact with the electrolyte solution; By being different, only infrared light reflected on the surface of the working electrode can be detected, and in-situ measurement with high detection accuracy is possible. Further, unlike the conventionally known technique of the high sensitivity infrared absorption reflection method, it is not necessary to strongly press the working electrode against the window material. Furthermore, since a relatively large amount of electrolyte exists between the surface of the window material that contacts the electrolyte and the surface of the working electrode that contacts the electrolyte, the gap between the working electrode and the counter electrode Therefore, the current density distribution is less likely to occur because of the diffusion of the electrolyte solution in the substrate. Therefore, electrochemical measurement at a high sweep rate and electrochemical measurement in a minute time are possible.

  It is preferable that the electrochemical infrared spectroscopic apparatus of the present invention is installed with the surface of the window material in contact with the electrolyte solution inclined with respect to the electrode surface of the working electrode in contact with the electrolyte solution.

  The electrochemical infrared spectroscopic device having such a configuration can be obtained by simply tilting the surface of the window material in contact with the electrolytic solution without changing the position and configuration of the already installed infrared light source and infrared light detector. Only infrared light reflected from the surface of the working electrode can be detected, and in-situ measurement with high detection accuracy is possible.

  In the electrochemical infrared spectrometer of the present invention, it is preferable that the window material is hemispherical or semi-cylindrical, and infrared light is incident from a convex surface portion of the window material.

  The electrochemical infrared spectroscopic apparatus having such a configuration can narrow the spot diameter of infrared light to a minute region without defocusing.

  As one form of the electrochemical infrared spectroscopic device of the present invention, the window material has a hexahedral shape, a surface of the window material that contacts the electrolyte solution, and a surface of the window material opposite to the electrolyte solution side. Can be configured to be not parallel.

  The electrochemical infrared spectroscopic device having such a configuration naturally installs the electrode surface of the working electrode in contact with the electrolytic solution and the surface of the window material opposite to the electrolytic solution side in a natural manner. An arrangement in which the surface of the window material in contact with the electrolytic solution and the electrode surface of the working electrode in contact with the electrolytic solution are not parallel and have a certain angle can be easily taken.

  In the electrochemical infrared spectroscopic device of the present invention, an angle formed between a surface of the window material in contact with the electrolytic solution and an electrode surface of the working electrode in contact with the electrolytic solution is 0.1 to 5 °. preferable.

  The electrochemical infrared spectroscope having such a configuration is such that the intensity of infrared light reflected on the surface of the working electrode is not weakened by infrared absorption by the electrolytic solution, and the red light reflected on the surface of the working electrode is not affected. Only external light can be detected.

  According to the present invention, since the surface of the window material that contacts the electrolyte solution and the electrode surface of the working electrode that contacts the electrolyte solution are not parallel, the electrode surface travels straight from the window material and does not undergo total reflection. The direction of the infrared light that has reached the electrode and reflected by the electrode surface is different from the direction of the infrared light that is incident on the window material and totally reflected on the surface of the window material that is in contact with the electrolyte solution. Only infrared light reflected on the surface can be detected, and in-situ measurement with high detection accuracy is possible. Further, unlike the conventionally known technique of the high sensitivity infrared absorption reflection method, it is not necessary to strongly press the working electrode against the window material. Furthermore, since a relatively large amount of electrolyte exists between the surface of the window material that contacts the electrolyte and the surface of the working electrode that contacts the electrolyte, the gap between the working electrode and the counter electrode Therefore, the current density distribution is less likely to occur because of the diffusion of the electrolyte solution in the substrate. Therefore, electrochemical measurement at a high sweep rate and electrochemical measurement in a minute time are possible.

  The electrochemical infrared spectroscopic device of the present invention has a working electrode, a counter electrode paired with the working electrode, a reference electrode for regulating the potential of the working electrode, and a window material into which infrared light is incident. In addition, an electrolyte exists in the gap between the working electrode and the window material, and infrared light traveling straight from the window material enters the electrolyte without being totally reflected, and comes into contact with the electrolyte of the working electrode An electrochemical infrared spectroscopic apparatus that measures the reflected light intensity of infrared light from the electrode surface in situ by reaching the electrode surface, reflecting on the electrode surface, and reaching the detector, wherein the window material The surface of the working electrode in contact with the electrolytic solution and the surface of the working electrode in contact with the electrolytic solution are not parallel.

The working electrode is an electrode that actually exchanges electrons with the electrolytic solution. In particular, in the case of the present invention, since it is an apparatus that measures in situ changes in the surface of the working electrode itself in an electrode reaction, it is possible to select the type of electrode material suitable for the purpose. For example, when it is desired to measure an electrode reaction in a lithium ion secondary battery, LiCoO ₂ , LiMnO ₄ , LiNiO ₂ , LiNi _0.8 Co _0.2 O ₂ , Li (NiCoMn) O ₂ or the like can be used.
In addition, the electrode surface which contacts the electrolyte solution of a working electrode needs to be grind | polished beforehand. The reason is that, in this method, infrared light is reflected on the electrode surface, so that it is necessary to obtain a sufficient reflectance. Examples of the polishing method include buffing and CMP.

  The counter electrode is an electrode for returning the same current value as that generated at the working electrode to the system, and requires a much larger surface area than the working electrode. Specifically, in a mesh platinum electrode, a coil platinum electrode, a mesh nickel electrode, a coil nickel electrode, a mesh SUS electrode, a coil SUS electrode, or an electrolyte for a lithium ion secondary battery, Li An electrode to which a metal is attached can be used.

The reference electrode is an electrode that serves as a reference when determining the potential of the working electrode. A saturated calomel (mercury) electrode (Hg / Hg ²⁺ ), a silver electrode (Ag / AgCl), and a Li metal electrode (in the case of an electrolyte for a lithium ion secondary battery) can be used.

Basically, any solvent can be used as the electrolytic solution. In particular, in the case of the present invention, since it is an apparatus for observing changes in the surface of the working electrode, measurement can be performed without depending on the potential window of the solvent. For example, when it is desired to observe an electrode reaction in a lithium ion secondary battery, a LiPF ₆ solution or a LiBF ₄ solution can be used.
In addition, dehydration and deaeration may be necessary depending on the measurement target.

FIG. 1 is a schematic cross-sectional view showing the positional relationship of window materials, electrolytic solutions and working electrodes, and the path of infrared light in the electrochemical infrared spectroscopic apparatus of the present invention. The window material is an example using a hemispherical or semi-cylindrical shape, and the infrared light is assumed to run on the paper surface. In practice, the infrared light path connects one point on the semicircular arc of the window material and the vicinity of the center of the semicircle. In FIG. 1, the reflection and refraction are clearly shown. The outside light path is shifted and plotted. In addition, when using a semi-cylindrical window material, the semicircle surface which the said semi-cylindrical window material has shall be installed in the direction which becomes parallel to a paper surface.
The working electrode 1 and the window material 2 are installed such that the angle formed between the electrode surface 1a in contact with the electrolytic solution of the working electrode and the surface of the hemispherical or semi-cylindrical window material 2 in contact with the electrolytic solution 3 is θ. Yes. The electrolyte 3 is present around the working electrode and in the gap between the surface 1 a and the window material 2. The surface 1a and the surface of the window material 2 in contact with the electrolyte solution 3 do not have to be in contact with each other, but even if they are in contact, the effect of the present invention is not impaired.
Incident light 4 enters the electrolyte solution 3 at an angle θ ₁ and is refracted at an angle θ ₂ at the interface between the window material 2 and the electrolyte solution 3. At this time, total reflection in the window material 2 also occurs at the same time, and the total reflection angle is θ ₁ which is the same as the incident angle.
Infrared light refracted at an angle θ ₂ is reflected by the surface 1 a, then enters the window member 2 at an angle θ ₃ at the interface between the electrolytic solution 3 and the window member 2, and is refracted at an angle θ ₄ . After that, it exits the window material 2 and is detected by a detector.
At this time, the reflected light 5 exits the window material 2 at an angle θ ₄ from the normal line on the surface of the window material 2 that is in contact with the electrolyte solution 3, whereas the total reflected light 6 is emitted from the window material 2. The window material 2 exits at an angle θ ₁ from the normal line on the surface in contact with the electrolytic solution 3. Accordingly, since the reflected light 5 and the totally reflected light 6 travel in different directions, only the reflected light 5 can be detected.

FIG. 12 is a schematic cross-sectional view showing the positional relationship between the window material, the electrolytic solution and the working electrode, and the path of the infrared light in the electrochemical infrared spectroscopic apparatus using the conventional method of the high sensitivity infrared absorption reflection method. is there. In FIG. 12, the infrared light path is shifted as in FIG.
In this conventional method, the electrolyte 3 exists in the gap between the electrode surface 1a in contact with the electrolytic solution of the working electrode and the hemispherical or semi-cylindrical window material 2 that is a window material, and the surface 1a, the window The surface of the material 2 in contact with the electrolyte is parallel. When the configuration of this conventional technique is used, when the incident light 4 enters the electrolytic solution 3 at an angle θ ₁ at the interface between the window material 2 and the electrolytic solution 3, the reflected light 7 on the working electrode 1 and All the totally reflected light 8 in the window material 2 exits the window material 2 at an angle θ ₁ from the normal line on the surface of the window material 2 in contact with the electrolytic solution 3. Therefore, since the reflected light 7 and the total reflected light 8 travel in the same direction, it is not possible to detect only the reflected light 7, and observation with high detection accuracy cannot be expected.

Thus, the electrochemical infrared spectroscopic device of the present invention is such that the surface of the window material in contact with the electrolyte solution and the electrode surface of the working electrode in contact with the electrolyte solution are not parallel, and thus travels straight from the window material. The direction of the infrared light that reaches the electrode surface without being totally reflected and is reflected by the electrode surface is incident on the window material, and is different from the direction of the infrared light totally reflected on the window material, Only infrared light reflected on the surface of the working electrode can be detected, and in-situ measurement with high detection accuracy is possible.
In the conventionally known method of the high sensitivity infrared absorption reflection method, the reflected light on the surface of the working electrode and the total reflected light on the window material are detected simultaneously as shown in FIG. In order to obtain only the spectrum of the reflected light from the substrate efficiently, it is indispensable to press the working electrode strongly against the window material and to reduce the thickness of the layer formed by the electrolyte as much as possible. However, in the present invention, only the reflected light on the surface of the working electrode can be detected for the reason described above, and therefore it is not necessary to strongly press the working electrode against the window material.
Furthermore, in the conventional method of pressing the working electrode strongly against the window material, the thickness of the layer formed by the electrolytic solution is thin, so that the electrolytic solution is unlikely to diffuse between the electrode surface in contact with the electrolytic solution of the working electrode and the counter electrode. Therefore, a so-called current density distribution in which the current density is different between the central portion and the end portion of the electrode surface in contact with the electrolytic solution of the working electrode is likely to occur. However, in the present invention, a relatively large amount of electrolyte exists between the surface of the window material that contacts the electrolyte and the surface of the working electrode that contacts the electrolyte. Since the electrolyte solution easily diffuses between the counter electrodes, a current density distribution is unlikely to occur. Therefore, electrochemical measurement at a high sweep rate and electrochemical measurement in a minute time are possible.

  As shown in FIG. 1, it is preferable that the surface of the window material in contact with the electrolytic solution is inclined with respect to the surface of the working electrode in contact with the electrolytic solution. This is because the infrared light reflected from the surface of the working electrode can be obtained by simply tilting the surface of the window material in contact with the electrolyte without changing the position or configuration of the infrared light source and infrared light detector that are already installed. This is because only light can be detected, and in-situ measurement with high detection accuracy is possible.

  Furthermore, as shown in FIG. 1, it is preferable that the window material has a hemispherical shape or a semi-cylindrical shape, and infrared light is incident from a convex surface portion of the window material. This is because the spot diameter of infrared light can be narrowed down to a minute region without defocusing.

It is preferable that an angle θ formed by a surface of the window material in contact with the electrolytic solution and an electrode surface of the working electrode in contact with the electrolytic solution is 0.1 to 5 °.
If the angle θ is less than 0.1 °, only the infrared light reflected by the surface of the working electrode, which is the effect of the present invention, cannot be detected, and the detection accuracy cannot be improved. Further, precisely controlling the angle θ of less than 0.1 ° has a limit on the processing accuracy of the apparatus or window material.
If the angle θ exceeds 5 °, the layer of the electrolyte present in the gap between the electrode surface of the working electrode in contact with the electrolyte and the window material becomes too thick, so that the infrared light reflected on the surface of the working electrode is reflected. The intensity of light is weakened by infrared absorption by the electrolytic solution, and infrared light having the expected intensity cannot be detected.
The angle θ is more preferably 0.3 ° to 3 °, and most preferably 1 ° to 3 °.

  FIG. 2 is a schematic cross-sectional view showing the positional relationship between a hexahedral window material, an electrolytic solution and a working electrode, and a path of infrared light, which is an embodiment of the electrochemical infrared spectrometer of the present invention. As the hexahedral window material, a window material in which the surface of the window material in contact with the electrolyte solution and the surface of the window material opposite to the electrolyte solution side are not parallel is used.

The working electrode 11 and the hexahedral window material 12 are installed so that the electrode surface 11a of the working electrode in contact with the electrolytic solution and the surface of the hexahedral window material 12 opposite to the electrolyte side are parallel to each other. At this time, if the angle formed between the surface of the window member 12 in contact with the electrolyte solution 13 and the surface of the window member 12 opposite to the electrolyte solution 13 side is θ, the surface 11a and the window member 12 The angle formed with the surface in contact with the electrolytic solution 13 is also set to θ naturally. The surface 11a and the surface of the window member 12 that are in contact with the electrolyte solution 13 do not need to be in contact with each other, but the effect of the present invention is not impaired even if they are in contact.
Incident light 14 is incident on the electrolyte solution 13 at an angle θ ₅ and refracted at an angle θ ₆ at the interface between the window material 12 and the electrolyte solution 13. At this time, total reflection into the window material 12 also occurs at the same time, and the total reflection angle is θ ₅ which is the same as the incident angle.
Infrared light refracted at an angle θ ₆ is reflected by the surface 11 a, then enters the window member 12 at an angle θ ₇ at the interface between the electrolytic solution 13 and the window member 12, and is refracted at an angle θ ₈ . Then, it exits the window member 12 and is detected by a detector.
At this time, the reflected light 15 exits the window material 12 at an angle θ ₈ from the normal of the surface of the window material 12 that contacts the electrolyte solution 13, whereas the total reflected light 16 reflects the above-described window material 12. The window member 12 exits at an angle θ ₅ from the normal line of the surface in contact with the electrolytic solution 13. Therefore, since the reflected light 15 and the total reflected light 16 travel in different directions, only the reflected light 15 can be detected.

  Thus, the electrode surface of the working electrode in contact with the electrolyte solution and the surface of the window material opposite to the electrolyte solution side are placed in parallel, so that the window material is naturally in contact with the electrolyte solution. An arrangement in which the surface and the electrode surface of the working electrode in contact with the electrolytic solution are not parallel and has a certain angle can be easily taken.

FIG. 3 shows the angle of the window material, the positional relationship between the electrolyte solution and the working electrode, and the infrared light when a hexahedral window material, which is an embodiment of the electrochemical infrared spectrometer of the present invention, is used. It is the cross-sectional schematic diagram which described the path | route.
As shown in FIG. 3, it is preferable that the angles formed by the surface of the window member on the side opposite to the electrolyte solution side and the four surfaces sharing the side with the surface are the same angle α. This is because the incident light from the infrared light source to the window material and the reflected light emitted from the window material and detected by the detector are incident at an equal angle with respect to the electrode surface of the working electrode in contact with the electrolyte solution. This is because it is preferable to reflect. α = 95 ° to 135 ° is more preferable, and α = 100 ° to 125 ° is most preferable.

As the shape of the window material, in addition to the above-described hemispherical shape and semicylindrical shape, a quadrangular pyramid shape, a trapezoidal column shape, or the like can be used. In the schematic cross-sectional view shown in FIG. 3, the shape of the window material is not limited to the hexahedral shape described above as long as the angle α satisfies the above-described conditions.
As the material used for the window material, materials conventionally used in the high-sensitivity infrared absorption reflection method can be used. For example, the absolute refractive index of CaF ₂ , BaF ₂ , MgF ₂ , NaCl, etc. is 1.4 to It is preferable to use 1.5.
Note that the window material needs to be optically polished on the side where infrared light enters and exits.

  The working electrode according to the present invention preferably has a diameter of 1 mmφ to 50 mmφ. This is because if the diameter is less than 1 mmφ, the size of the working electrode approaches that of a microelectrode, so there is a possibility that the rate-determining stage is different from the electrochemical reaction originally desired, and if the diameter exceeds 50 mmφ. This is because the current distribution in the electrode surface is not uniform and the potential is not constant. In addition, the diameter of the working electrode is more preferably 2 mmφ to 30 mmφ, and most preferably 3 mmφ to 20 mmφ.

  Hereinafter, typical examples of the present invention will be described in detail with reference to the drawings. FIG. 4 is a schematic cross-sectional view showing the configuration of an electrochemical infrared spectroscopic apparatus which is a typical example of the present invention, and shows a case where a hemispherical window material is used. Note that the refraction of infrared light at the interface between the window material and the electrolyte shown in FIGS. 1 to 3 is negligibly small from the scale of the entire apparatus, and thus is not considered in the drawings.

First, the electrochemical cell is assembled. Since the positions of the working electrode 21, the counter electrode 31, and the reference electrode 32 in the cell are restricted by electrochemical conditions and the position of the optical system used for measurement, it is necessary to strictly determine the positions.
After determining the positions of these electrodes, the hemispherical window material 22 whose surface has been optically polished is set at an angle θ with respect to the electrode surface 21a of the window material 22 in contact with the electrolyte solution of the working electrode. Tilt it so that it becomes. At this time, it is preferable that the side surface of the cell is set in advance so that the window member 22 can be inclined. In addition, in order to increase the diffusion of the electrolytic solution between the working electrode and the counter electrode, the counter electrode 31 is installed on the side farthest from the surface 21a and the surface of the window member 22 that contacts the electrolytic solution. Is preferred. Furthermore, when performing electrochemical measurement under an inert atmosphere, it is necessary to incorporate an O-ring 35 between the side surface of the cell and the window material 22 to improve the airtightness in the cell. After the window material 22 is installed, the window material 22 is fixed by the window material installation base 36 and the metal fitting 37.
After fixing the window material 22, if necessary, the inside of the cell is replaced with an inert gas, and then the necessary amount of electrolyte is added, and the above-described electrodes can be set with the potential and current value between the electrodes. As a result, the assembly of the electrochemical cell is completed.

An existing infrared spectrometer can be used as the optical system. The optical system shown in FIG. 4 is an outline thereof, and may actually have a more complicated configuration than shown.
As the infrared spectrometer, a Fourier transform infrared spectrophotometer (FT-IR), a dispersive infrared spectrophotometer, or the like can be used. However, highly sensitive analysis is possible and analysis is performed in units of several seconds. In addition, it is preferable to use FT-IR because the wave number accuracy and wave number reproducibility are good.

  The measuring method is as follows. The infrared light 24 emitted from the light source is collected by the concave mirror 33 and then enters the hemispherical window material 22. Hereinafter, the process until the infrared light is reflected on the electrode surface 21a in contact with the electrolytic solution of the working electrode and the reflected light 25 is emitted from the hemispherical window member 22 is as shown in FIG. Since the reflected light 25 and the total reflected light 26 totally reflected by the surface of the window material 22 in contact with the electrolytic solution 23 are emitted in different directions, only the reflected light 25 is collected by the concave mirror 34. can do. The collected reflected light 25 is detected by a detector, and a desired spectrum can be obtained by performing a fast Fourier transform.

Hereinafter, modifications of the present invention will be described with reference to the drawings. FIG. 5 is a schematic cross-sectional view showing the configuration of an electrochemical infrared spectrometer that is a modification of the present invention, and is a view showing a case where a hexahedral window material is used. As in FIG. 4, the refraction of infrared light at the interface between the window material and the electrolytic solution is not considered in the figure.
In the configuration of the electrochemical infrared spectroscopic device shown in FIG. 5, the hemispherical window material 22 of the typical example shown in FIG. 4 is replaced with a hexahedral window material 42 in which at least the surface where infrared light enters and exits is optically polished. It is a configuration. Unlike the hemispherical window material 22 used in the typical example, the hexagonal window material 42 has an angle θ that can be measured in advance. Therefore, the window material 42 suitable for measurement is prepared for each desired angle θ. There is a need. Further, when the window member 42 is fixed by the window member mounting base 36 and the metal fitting 37, the surface of the working electrode in contact with the electrolyte solution and the surface of the window member 42 opposite to the electrolyte solution side are formed. It is necessary to install so that it is parallel.
The optical system and the measurement method are the same as the above-described typical example.

The electrochemical infrared spectroscopic device having such a configuration is such that the surface of the window material that contacts the electrolyte and the electrode surface of the working electrode that contacts the electrolyte are not parallel, and thus travels straight from the window material and is totally reflected. Without reaching the electrode surface, the direction of infrared light reflected on the electrode surface is incident on the window material, and is different from the direction of infrared light totally reflected on the surface of the window material in contact with the electrolyte solution, Only infrared light reflected on the surface of the working electrode can be detected, and in-situ measurement with high detection accuracy is possible. Further, unlike the conventionally known technique of the high sensitivity infrared absorption reflection method, it is not necessary to strongly press the working electrode against the window material. Furthermore, since a relatively large amount of electrolyte exists between the surface of the window material in contact with the electrolyte and the surface of the working electrode in contact with the electrolyte, between the working electrode and the counter electrode Therefore, the current density distribution is less likely to occur. Therefore, electrochemical measurement at a high sweep rate and electrochemical measurement in a minute time are possible.
In addition, the infrared light reflected on the surface of the working electrode can be obtained simply by tilting the surface of the window material in contact with the electrolytic solution without changing the position and configuration of the infrared light source and infrared light detector that are already installed. In-situ measurement with high detection accuracy is possible.
Furthermore, since the window material has a hemispherical shape or a semicylindrical shape, the spot diameter of infrared light can be narrowed down to a minute region without blurring the focal point.
The window material is hexahedral as described above, so that the electrode surface of the working electrode in contact with the electrolyte solution and the surface of the window material opposite to the electrolyte solution side are installed in parallel. Accordingly, it is possible to easily take an arrangement in which the surface of the window material in contact with the electrolyte solution and the electrode surface of the working electrode in contact with the electrolyte solution are not parallel and have a certain angle.
In addition, the infrared light reflected on the surface of the working electrode is formed by forming an appropriate angle as described above between the surface of the window material in contact with the electrolytic solution and the electrode surface of the working electrode in contact with the electrolytic solution. Is not weakened by infrared absorption by the electrolytic solution, and only infrared light reflected on the surface of the working electrode can be detected.

1. In-situ measurement of working electrode surface In-situ FT-IR measurement of the working electrode surface was performed using the configuration of the electrochemical infrared spectroscopic apparatus of the above-described typical example (FIG. 4). Electrochemical cell conditions, electrochemical apparatus conditions, and measurement conditions are as follows.

[Example 1]
(Electrochemical cell conditions)
Working electrode: LiCoO ₂ thin film (on Au substrate)
Working electrode diameter: 15mmφ
Counter electrode: Li metal Reference electrode: Li metal Electrolyte: LiPF ₆ solution (1M, EC: DEC = 1: 1 (vol / vol))
Window material: BaF ₂ (semispherical window material), high polishing accuracy Angle θ: 1 °
Remarks: None (Electrochemical equipment conditions)
Open circuit potential, FT-IR measurement after standing for 3 hours.
(FT-IR measurement conditions)
Measurement data type: Single beam spectrum Integration count: 100 times Resolution: 8 cm ^-1
Polarized light: p-polarized light

[Example 2]
(Electrochemical cell conditions)
Angle θ: 3 °
Remarks: None Other electrochemical cell conditions, electrochemical apparatus conditions, and FT-IR measurement conditions are the same as in Example 1.

[Comparative Example 1]
(Electrochemical cell conditions)
Angle θ: 0 °
Remarks: The working electrode was strongly pressed against the window material to eliminate as much as possible the gap between the working electrode and the window material.
Other electrochemical cell conditions, electrochemical apparatus conditions, and FT-IR measurement conditions are the same as in Example 1.

[Comparative Example 2]
(Electrochemical cell conditions)
Angle θ: 0 °
Remarks: One polypropylene microporous film having a thickness of 0.1 mm was sandwiched between portions other than the infrared light path between the working electrode and the window material.
Other electrochemical cell conditions, electrochemical apparatus conditions, and FT-IR measurement conditions are the same as in Example 1.

[Comparative Example 3]
(Electrochemical cell conditions)
Angle θ: 0 °
Remarks: Two polypropylene microporous films having a thickness of 0.1 mm were sandwiched between portions other than the infrared light path between the working electrode and the window material.
Other electrochemical cell conditions, electrochemical apparatus conditions, and FT-IR measurement conditions are the same as in Example 1.

[Comparative Example 4]
(Electrochemical cell conditions)
Angle θ: 0 °
Remarks: A space of 5 mm was provided between the working electrode and the window material.
Other electrochemical cell conditions, electrochemical apparatus conditions, and FT-IR measurement conditions are the same as in Example 1.

2. Consideration of Measurement Results FIGS. 6 to 11 are diagrams showing the FT-IR measurement results of Examples 1 and 2 and Comparative Examples 1 to 4, respectively.
In Comparative Example 1 (θ = 0 °), the working electrode is strongly pressed against the window material and the gap between the working electrode and the window material is eliminated as much as possible. Therefore, the electrolyte layer entering the gap is extremely thin, and the electrolyte solution Absorption of the reflected light from the working electrode due to is hardly caused. Therefore, the intensity of the reflected light from the working electrode is higher than the intensity of the totally reflected light in the window material. Since θ = 0 °, both the reflected light from the working electrode and the total reflected light on the window material reach the detector, but the shape of the spectrum that actually appears is the spectrum of the reflected light from the working electrode with high intensity. Shape. Therefore, FIG. 8 showing the result of Comparative Example 1 (θ = 0 °) is a spectrum of the reflected light from the working electrode. However, as described above, in the configuration of Comparative Example 1, a current density distribution is likely to occur, and therefore electrochemical measurement at a high sweep rate and electrochemical measurement in a minute time are impossible.
6 showing the results of Example 1 (θ = 1 °) and FIG. 7 showing the results of Example 2 (θ = 3 °) are shown in FIG. 8 showing the results of Comparative Example 1 (θ = 0 °). It shows almost the same spectrum shape. Therefore, even if the electrolyte exists in the gap between the working electrode and the window material, a good in situ measurement FT-IR spectrum can be obtained by tilting the window material. It shows that you can get.
On the other hand, FIG. 11 showing the result of Comparative Example 4 (with a space of 5 mm between the working electrode and the window material) shows a spectrum shape completely different from that of FIGS. This is because the reflected light from the working electrode is absorbed by the electrolyte present in the gap of 5 mm between the working electrode and the window material, so it does not reach the detector, but instead only the total reflected light from the window material is detected. Indicates that Therefore, FIG. 11 is an absorption spectrum of BaF ₂ used for the window material.
Further, as in Comparative Example 2 or 3, in the case where a polypropylene microporous film usually used as a separator for a lithium battery is sandwiched between portions other than the infrared light path between the working electrode and the window material, FIG. 9 or FIG. As shown in FIG. 6, the spectrum shape is different from that of FIGS. In other words, when θ = 0 °, by providing a layer of an electrolytic solution having a thickness of 1 mm or more between the working electrode and the window material, the reflected light from the working electrode is absorbed by the electrolytic solution and the strength is reduced. This shows that when the intensity of the totally reflected light from the window material becomes stronger, the spectrum of the reflected light cannot be detected well.

3. Summary From this example, in the electrochemical infrared spectroscopic device of the present invention, the window material should be inclined with respect to the surface of the working electrode even if an electrolyte exists in the gap between the working electrode and the window material. Thus, it was clarified that a good in-situ measured FT-IR spectrum can be obtained without being affected by the total reflection light from the window material.

It is the cross-sectional schematic diagram which described the positional relationship of the window material, electrolyte solution, and a working electrode in the electrochemical infrared spectroscopy apparatus of this invention, and the path | route of infrared light. It is the cross-sectional schematic diagram which described the positional relationship of the hexahedral window material, electrolyte solution, and a working electrode which is one form of the electrochemical infrared spectroscopy apparatus of this invention, and the path | route of infrared light. Described are the angle of the window material, the positional relationship between the electrolyte and working electrode, and the path of infrared light when using a hexahedral window material, which is a form of the electrochemical infrared spectrometer of the present invention. It is a cross-sectional schematic diagram. It is the cross-sectional schematic diagram which showed the structure of the electrochemical infrared spectroscopy apparatus which is a typical example of this invention, and is the figure which showed the case where a hemispherical window material was used. It is the cross-sectional schematic diagram which showed the structure of the electrochemical infrared spectroscopy apparatus which is a modification of this invention, and is the figure which showed the case where a hexahedral-shaped window material is used. FIG. 4 is a diagram showing the FT-IR measurement results of Example 1. It is a figure which shows the FT-IR measurement result of Example 2. It is a figure which shows the FT-IR measurement result of the comparative example 1. It is a figure which shows the FT-IR measurement result of the comparative example 2. It is a figure which shows the FT-IR measurement result of the comparative example 3. It is a figure which shows the FT-IR measurement result of the comparative example 4. It is the cross-sectional schematic diagram which described the positional relationship of the window material, electrolyte solution, and a working electrode, and the path | route of infrared light in the electrochemical infrared spectroscopy apparatus using the conventional technique of the high sensitivity infrared absorption reflection method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Working electrode 1a ... Electrode surface 2 in contact with electrolyte of working electrode 2 ... Semispherical or semi-cylindrical window material 3 ... Electrolyte 4 ... Incident light 5 ... Reflected light 6 ... Total reflected light 7 ... Reflected light 8 ... Total reflected Light 11 ... Working electrode 11a ... Electrode surface 12 in contact with electrolyte of working electrode ... Hexahedral window material 13 ... Electrolytic solution 14 ... Incident light 15 ... Reflected light 16 ... Total reflected light 21 ... Working electrode 21a ... Electrolytic solution of working electrode Electrode surface 22 in contact with hemispherical window material 23 ... Electrolyte solution 24 ... Incident light 25 ... Reflected light 26 ... Total reflected light 31 ... Counter electrode 32 ... Reference electrode 33, 34 ... Concave mirror 35 ... O-ring 36 ... Window material installation base 37 ... metal fitting 42 ... hexahedral window material

Claims (5)

A working electrode; a counter electrode that forms a pair with the working electrode; a reference electrode for regulating the potential of the working electrode; and a window member into which infrared light is incident. The working electrode and the window member Electrolytic solution exists in the gap, and the infrared light traveling straight from the window material enters the electrolytic solution without being totally reflected, reaches the electrode surface of the working electrode in contact with the electrolytic solution, and is reflected by the electrode surface An electrochemical infrared spectroscopic apparatus that measures the reflected light intensity of infrared light from the electrode surface in situ by reaching the detector,
The electrochemical infrared spectroscopic apparatus characterized in that a surface of the window material in contact with the electrolytic solution and an electrode surface of the working electrode in contact with the electrolytic solution are not parallel.   2. The electrochemical infrared spectroscopic apparatus according to claim 1, wherein a surface of the window material in contact with the electrolyte solution is inclined with respect to an electrode surface of the working electrode in contact with the electrolyte solution.   The electrochemical infrared spectrometer according to claim 1 or 2, wherein the window material is hemispherical or semi-cylindrical, and infrared light is incident from a convex surface portion of the window material.   The electrochemical according to claim 1 or 2, wherein the window material has a hexahedral shape, and a surface of the window material in contact with the electrolyte solution and a surface of the window material opposite to the electrolyte solution side are not parallel. Infrared spectrometer.   5. The angle formed by a surface of the window material in contact with the electrolyte solution and an electrode surface of the working electrode in contact with the electrolyte solution is 0.1 to 5 °. Electrochemical infrared spectroscopic device.

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