CN-116710767-B - Electrochemical oxygen sensor and method for manufacturing the same

Abstract

The electrochemical oxygen sensor of the present invention comprises a positive electrode, a negative electrode, and an electrolyte solution comprising an aqueous solution, wherein the negative electrode comprises a metal containing an element M selected from Sn and Ni as a main component, the electrolyte solution is an aqueous solution having a pH of 3 to 10, the positive electrode comprises a catalyst layer comprising a catalyst metal, and the catalyst layer comprises a surface layer comprising the element M on a surface in contact with the electrolyte solution.

Inventors

• WATANABE MITSUTOSHI
• KITAZAWA NAOHISA
• IWANAMI RYOJI

Assignees

• 麦克赛尔株式会社

Dates

Publication Date

20260505

Application Date

20210309

Priority Date

20201125

Claims (15)

1. 1. An electrochemical oxygen sensor comprises a positive electrode, a negative electrode and an electrolyte composed of an aqueous solution, wherein, The negative electrode contains a metal containing an element M selected from Sn and Ni and serving as a main component, the content of the element M in the metal is more than 50% by mass, The electrolyte is an aqueous solution with pH of 3-10, The positive electrode includes a catalyst layer containing a catalyst metal, The catalyst layer includes a surface layer containing the element M on a surface in contact with the electrolyte.
2. 2. The electrochemical oxygen sensor of claim 1, wherein the catalyst layer of the positive electrode contains gold.
3. 3. An electrochemical oxygen sensor according to claim 1 or 2, wherein the electrolyte contains a chelating agent.
4. 4. The electrochemical oxygen sensor of claim 1 or 2, wherein the negative electrode comprises Sn or an alloy of Sn.
5. 5. The electrochemical oxygen sensor of claim 4, wherein the catalyst metal of the catalyst layer comprises Au and the surface layer comprises Sn and Au.
6. 6. An electrochemical oxygen sensor according to claim 1 or 2, wherein the element M is contained in the surface layer in an amount of 10 μg/cm 2 or more and 10mg/cm 2 or less per unit area.
7. 7. The electrochemical oxygen sensor of claim 1 or 2, wherein the electrolyte is an acidic aqueous solution containing a carboxylic acid or salt thereof.
8. 8. An electrochemical oxygen sensor according to claim 3, wherein the chelating agent comprises 1 or 2 or more selected from the group consisting of citric acid, tartaric acid, glutamic acid, and salts thereof.
9. 9. An electrochemical oxygen sensor according to claim 3, wherein the concentration of the chelating agent in the electrolyte is 2.3mol/L or more.
10. 10. An electrochemical oxygen sensor according to claim 3, wherein the electrolyte further comprises ammonia.
11. 11. The electrochemical oxygen sensor of claim 10, wherein the concentration of ammonia in the electrolyte is 0.1mol/L or more.
12. 12. A method for manufacturing an electrochemical oxygen sensor according to claim 1 or 2, comprising: A sensor assembly step of assembling an electrochemical oxygen sensor using a positive electrode including a catalyst layer containing a catalyst metal, a negative electrode including a metal containing an element M that is a main component selected from Sn and Ni, and an electrolyte solution composed of an aqueous solution having a pH of 3 to 10, and And a surface layer forming step of forming a surface layer containing the element M on the surface of the positive electrode before or after the sensor assembly step.
13. 13. The method for manufacturing an electrochemical oxygen sensor according to claim 12, wherein the step of forming the surface layer includes a step of supplying a gas having an oxygen concentration of 0.3 vol.% or less to the positive electrode in a state where the positive electrode and the negative electrode are electrically connected after the step of assembling, thereby forming the surface layer by precipitating the element M from the electrolyte on a surface of the catalyst layer of the positive electrode, the surface being in contact with the electrolyte.
14. 14. The method for manufacturing an electrochemical oxygen sensor according to claim 13, wherein the gas supplied to the positive electrode does not contain oxygen.
15. 15. The method of manufacturing an electrochemical oxygen sensor of claim 12, wherein the negative electrode comprises Sn or an alloy of Sn.

Description

Electrochemical oxygen sensor and method for manufacturing the same Technical Field The present invention relates to an electrochemical oxygen sensor having improved measurement reliability in a gas having a low oxygen concentration, and a method for manufacturing the same. Background Electrochemical oxygen sensors (hereinafter also referred to as oxygen sensors) are used in a wide range of fields such as inspection of an anoxic state in a cabin or in an manhole, detection of an oxygen concentration in medical equipment such as an anaesthesia machine and a breathing machine, because they are inexpensive, simple and capable of operating at normal temperature. As such an electrochemical oxygen sensor, for example, a sensor having an aqueous electrolyte solution and using Sn or an alloy thereof as a negative electrode is known (patent documents 1 and 2, etc.). Prior art literature Patent literature Patent document 1 Japanese patent laid-open No. 2006-194708 Patent document 2 Japanese patent application laid-open No. 2017-67596 Disclosure of Invention Problems to be solved by the invention In the electrochemical oxygen sensor, when oxygen intrudes into the inside, the oxygen is reduced at the positive electrode, and a metal elution reaction occurs at the negative electrode, whereby an electric current corresponding to the oxygen concentration is generated between the positive electrode and the negative electrode. Therefore, for example, the current generated by the positive electrode reaction (reduction of oxygen in the positive electrode) is converted into a voltage, and the oxygen concentration is obtained based on the voltage. Accordingly, when the electrochemical oxygen sensor is placed in an anaerobic environment, the above-described positive electrode reaction does not occur, and therefore the above-described current is not generated originally, and it is also possible to measure that the oxygen concentration is zero. However, in reality, although the measurement is carried out in an anaerobic environment, if the observation is continued for a certain period of time, a measurement result as if oxygen is present may be obtained. Therefore, depending on the structure of the oxygen sensor, there is a problem that it is difficult to use the oxygen sensor for measuring low concentration oxygen gas, and there is a problem that the measurement range of the oxygen concentration is limited. The present invention has been made in view of the above circumstances, and an object thereof is to provide an electrochemical oxygen sensor having improved reliability in measurement in a gas having a low oxygen concentration, and a method for manufacturing the same. Means for solving the problems The electrochemical oxygen sensor of the present invention comprises a positive electrode, a negative electrode, and an electrolyte solution comprising an aqueous solution, wherein the negative electrode comprises a metal containing an element M selected from Sn and Ni as a main component, the electrolyte solution is an aqueous solution having a pH of 3 to 10, the positive electrode comprises a catalyst layer containing a catalyst metal, and the catalyst layer comprises a surface layer containing the element M on a surface in contact with the electrolyte solution. The electrochemical oxygen sensor of the present invention can be manufactured by the manufacturing method of the present invention including a sensor assembly step and a surface layer forming step, wherein the electrochemical oxygen sensor is assembled by using a positive electrode including a catalyst layer containing a catalyst metal, a negative electrode including a metal containing an element M selected from Sn and Ni and serving as a main component, and an electrolyte solution composed of an aqueous solution having a pH of 3 to 10, and wherein the surface layer containing the element M is formed on the surface of the positive electrode before or after the sensor assembly step. Effects of the invention According to the present invention, it is possible to provide an electrochemical oxygen sensor having improved reliability in measuring the oxygen concentration of a gas having a low oxygen content, and a method for manufacturing the same. Drawings Fig. 1 is a graph showing a change in output voltage when an electrochemical oxygen sensor having a negative electrode containing Sn is used in an oxygen-free environment. FIG. 2 is a cross-sectional view schematically showing an example of an electrochemical oxygen sensor according to the present invention. FIG. 3A graph showing the results of characteristic evaluation tests of the electrochemical oxygen sensors of examples 1 to 2 and comparative example 1. Detailed Description As shown in fig. 1, the inventors of the present invention have studied and found that when an electrochemical oxygen sensor (hereinafter, may be simply referred to as "oxygen sensor") is used in an anaerobic environment, it is confirmed that the volta