Electrochemical sensor and application thereof

Abstract

The present invention provides an electrochemical sensor comprising: a plurality of electrodes forming ion conduction by an electrolyte, the plurality of electrodes comprising a working electrode, a reference electrode and a counter electrode, the electrolyte comprising a first electrolyte and a second electrolyte. According to the electrochemical sensor disclosed by the invention, the second electrolyte matched with the interference gas is added into the electrolyte to effectively inhibit the chemical reaction of the interference gas. Therefore, the oxidation-reduction reaction of the gas to be detected only occurs on the electrode as far as possible, and the purpose of enhancing the accuracy of the sensor is achieved.

Description

Technical Field

[0001] The invention relates to a gas detection device, in particular to an electrochemical sensor for detecting vehicle exhaust gas. Background Art

[0002] An electrochemical sensor is a gas detection device that uses a redox reaction on a sensing electrode to generate an electrical signal. It can be used to measure the gas concentration of the target gas. Under complex working conditions, it needs to have good consistency, repeatability and anti-interference. However, electrochemical sensors are still plagued by some technical difficulties and process limitations. As a result, their consistency will be reduced under different working conditions. Or they are susceptible to interference from other gases on the concentration.

[0003] During vehicle operation, a variety of gases harmful to the environment will be generated, such as sulfur dioxide (SO2), nitrogen monoxide (CO), and some volatile organic compounds (VOC). These toxic and harmful gases need to be detected; when lithium-ion batteries bulge and leak, the gases produced by the reaction need to be detected. This allows for a quick understanding of the battery status; during the production and disposal of lithium-ion batteries, the reaction gases need to be detected. This ensures the health of personnel and environmental safety.

[0004] In traditional electrochemical sensors, usually only one electrolyte is present to support redox reactions and ion diffusion. Summary of the invention

[0005] In order to improve the accuracy of the electrochemical sensor, the present invention adds a second electrolyte that matches the interfering gas to the electrolyte to effectively suppress the chemical reaction of the interfering gas, so that only the redox reaction of the gas to be measured occurs on the electrode as much as possible, thereby achieving the purpose of enhancing the accuracy of the sensor.

[0006] The establishment of chemical equilibrium is based on reversible reactions. Reversible reactions refer to reactions that can proceed both forward and reverse under the same conditions. Most chemical reactions are reversible and can reach equilibrium to varying degrees. Chemical equilibrium refers to a state in which the forward and reverse reaction rates of a chemical reaction are equal and the concentrations of the reactants and products do not change in a reversible reaction under certain macroscopic conditions. It can be judged by ΔrGm=ΣνΑμΑ=0, where μA is the chemical potential of substance A in the reaction. According to the Gibbs free energy criterion, when ΔrGm=0, the reaction reaches its maximum limit and is in equilibrium. According to Le Chatelier's principle, if a system that has reached equilibrium is changed, the system will change accordingly to counteract the change.

[0007] When other conditions remain unchanged, increasing the concentration of reactants or decreasing the concentration of products is conducive to the forward reaction and the equilibrium shifts to the right; increasing the concentration of products or decreasing the concentration of reactants is conducive to the reverse reaction and the equilibrium shifts to the left. The change in the concentration of a single substance only changes the reaction rate of one of the forward or reverse reactions, resulting in unequal forward and reverse reaction rates, which breaks the equilibrium. Therefore, a second electrolyte that matches the interfering gas can be added to the electrolyte of the electrochemical sensor to effectively suppress the chemical reaction of the interfering gas.

[0008] When the electrochemical sensor is injected with liquid, the corresponding electrolyte can be mixed for the interfering gas of the target gas of the sensor. The mixed liquid is used as the new electrolyte of the sensor. For example: if the interfering gas of the target gas is nitrogen dioxide (NO2), nitrate can be mixed into the electrolyte. Since the products of nitrogen dioxide (NO2) in the redox reaction are mostly nitrate ions, the presence of nitrate will affect the dynamic equilibrium in the redox reaction, thereby inhibiting the reaction of nitrogen dioxide (NO2). The reaction of the interfering gas on the electrode is further reduced to achieve the purpose of enhancing the accuracy of the electrochemical sensor. The electrolyte mixing ratio needs to be determined according to the chemical properties of the two electrolytes. Generally, the liquid volume of the second electrolyte needs to be lower than that of the first electrolyte. When mixing, the injection order needs to be considered to avoid the danger of mixing strong acid systems. The electrochemical sensor of the present invention can be a three-electrode or four-electrode system. The electrochemical sensor can be an upper and lower structure or a left and right structure. The electrochemical sensor can have a bias voltage.

[0009] Specifically, the present invention discloses an electrochemical sensor, comprising: a plurality of electrodes that form ion conduction through an electrolyte, the plurality of electrodes comprising a working electrode, a reference electrode and a counter electrode, and the electrolyte comprising a first electrolyte and a second electrolyte.

[0010] Preferably, the first electrolyte is sulfuric acid or phosphoric acid, and the second electrolyte is nitric acid or a nitrate solution.

[0011] Preferably, the liquid capacity of the second electrolyte is lower than that of the first electrolyte.

[0012] Preferably, the mixing volume ratio of the first electrolyte to the second electrolyte is 3:1 or 4:1 or 5:1.

[0013] Preferably, the electrochemical sensor further comprises: a shell, an air inlet is arranged on the top surface of the shell, and a plurality of pins are arranged on the bottom outer surface of the shell, wherein the plurality of pins are respectively connected to the plurality of electrodes for conducting with an external circuit.

[0014] Preferably, a filter, a breathable membrane, a working electrode, an electrolyte tank, a counter electrode and a reference electrode are arranged in sequence from top to bottom in the shell; the counter electrode and the reference electrode are relatively arranged on the same plane at the bottom of the electrolyte tank, and the electrolyte tank is used to contain the electrolyte; the filter is used to filter interfering gases and water vapor, and the gas to be measured passes through the air inlet, the filter and the breathable membrane in sequence before reaching the working electrode.

[0015] Preferably, a first air inlet and a second air inlet are provided at the top of the shell, a first filter and a first air permeable membrane are provided in sequence below the first air inlet; a second filter and a second air permeable membrane are provided in sequence below the second air inlet; a working electrode is provided below the first air permeable membrane, and an auxiliary electrode is provided below the second air permeable membrane; the working electrode and the auxiliary electrode are provided on the same plane, and are isolated in different spaces by adding a partition; an electrolyte tank is provided below the working electrode and the auxiliary electrode, the counter electrode and the reference electrode are relatively provided on the same plane at the bottom of the electrolyte tank, the filter is used to filter interfering gas and water vapor, the gas passing through the first air inlet can only reach the working electrode, and the gas passing through the second air inlet can only reach the auxiliary electrode. The auxiliary electrode has the same characteristics as the working electrode.

[0016] Preferably, the working electrode is a platinum-carbon electrode, the counter electrode is a platinum electrode, and the reference electrode is a silver chloride electrode.

[0017] The present invention also discloses a method for applying the electrochemical sensor to measure vehicle exhaust, battery bulging leakage, and gas detection during the production and waste treatment of lithium-ion batteries.

[0018] The electrochemical sensor of the present invention adds a second electrolyte that matches the interfering gas to its electrolyte to effectively suppress the chemical reaction of the interfering gas, so that only the redox reaction of the gas to be measured occurs on the electrode as much as possible, thereby achieving the purpose of enhancing the accuracy of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of an electrochemical sensor with a three-electrode upper and lower structure according to an embodiment of the present invention;

[0020] Figure 2 A schematic diagram of the response of an electrochemical sensor to an interfering gas NO2 in which no nitric acid or nitrate is added to the electrolyte according to an embodiment of the present invention;

[0021] Figure 3 A schematic diagram of the response of an electrochemical sensor to an interfering gas NO2 in which nitric acid or nitrate is added to an electrolyte according to an embodiment of the present invention;

[0022] Figure 4 Schematic diagram of an electrochemical sensor with four electrodes and left and right structures according to another embodiment of the present invention.

[0023] Reference numerals:

[0024] 1. Shell; 11. Air inlet; 12. Filter; 13. Breathable membrane; 14. Electrolyte tank; 2. Working electrode; 3. Counter electrode; 4. Reference electrode; 5. Pin; 6. Auxiliary electrode. DETAILED DESCRIPTION

[0025] The advantages of the present invention are further described below in conjunction with the accompanying drawings and specific embodiments.

[0026] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0027] The terms used in this disclosure are for the purpose of describing specific embodiments only and are not intended to limit the disclosure. The singular forms of "a", "said" and "the" used in this disclosure and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0028] It should be understood that although the terms first, second, third, etc. may be used in the present disclosure to describe various information, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present disclosure, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0029] In the description of the present invention, it is necessary to understand that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0030] In the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal connection between two components. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances.

[0031] In the following description, the suffixes such as "module", "component" or "unit" used to represent elements are only used to facilitate the description of the present invention, and have no specific meanings. Therefore, "module" and "component" can be used interchangeably.

[0032] See also Figure 1 This is a schematic diagram of the structure of an electrochemical sensor according to an embodiment of the present application. This embodiment shows that the electrochemical sensor of the present invention has three electrodes and an upper and lower structure.

[0033] Specifically, the electrochemical sensor includes: a housing 1, in which a filter 12, a gas permeable membrane 13, a working electrode 2 (including a working electrode electrode membrane; a working electrode catalyst), an electrolyte tank 14, a counter electrode 3 (including a counter electrode electrode membrane; a counter electrode catalyst) and a reference electrode 4 (including a reference electrode electrode membrane; a reference electrode catalyst) are arranged in order from top to bottom. The counter electrode 3 and the reference electrode 4 are arranged relatively on the same plane at the bottom of the electrolyte tank 14.

[0034] An air inlet 11 is provided on the top surface of the housing 1 to allow the interior of the housing 1 to circulate with the external environment. The aperture size of the air inlet 11 can control the sensitivity of the sensor. Those skilled in the art can adjust the aperture size of the air inlet 11 according to needs.

[0035] A filter 12 is provided below the air inlet 11. The filter 12 can be a single material or a mixture of several materials, such as activated carbon, potassium permanganate, etc. The main purpose is to filter some interfering gases and water vapor, reduce the interference of humidity on the sensitivity of the sensor, etc. In a specific implementation, the filter 12 contains activated carbon with a high specific surface area and alkaline alumina beads adsorbed with saturated potassium permanganate, which can be used to adsorb and oxidize some interfering gases. The same PTFE porous diaphragm as the working electrode 2 is used for sealing to control the amount of gas entering and prevent leakage of the electrolyte.

[0036] The outer bottom surface of the shell 1 is also provided with three pins 5, which are respectively connected to the working electrode 2, the counter electrode 3 and the reference electrode 4, and are used to conduct with the external circuit so that the sensor signal is output and transmitted to the external circuit.

[0037] The material of the sensor housing 1 can be ABS plastic, PP plastic, PC plastic, etc.

[0038] It should be noted that the working electrode 2, the reference electrode 4 and the counter electrode 3 are all gas diffusion electrodes, which may also include a small amount of binder, which can be added by those skilled in the art according to actual experience. Each electrode can be made by conventional techniques known in the art, and each electrode can be made by conventional techniques known in the art, for example, carbon and a binder such as Teflon can be pressed or sprayed on an electrode membrane, and then sintered. The electrode membrane can be a material known in the art, such as a polytetrafluoroethylene membrane, a polyvinyl chloride membrane, a polypropylene membrane, PTFE, etc.

[0039] Taking the ozone sensor as an example, the working electrode 2 is a platinum-carbon electrode, the counter electrode 3 is a platinum electrode, and the reference electrode 4 is a silver chloride electrode.

[0040] The electrolyte tank 14 is filled with electrolyte, and the electrolyte includes a first electrolyte and a second electrolyte. The first electrolyte and the second electrolyte are different according to the sensor type and the interfering gas type, and can be sulfuric acid, phosphoric acid, nitric acid / nitrate solution, etc. Those skilled in the art can select the appropriate first and second electrolytes according to the different types of the gas to be measured and the interfering gas, and both should fall within the scope of protection of the present invention.

[0041] When injecting liquid into the electrochemical sensor, the corresponding electrolyte can be mixed for the interfering gas of the target gas of the sensor. The mixed liquid is used as the new electrolyte of the sensor. For example, if the interfering gas of the target gas is nitrogen dioxide (NO2), nitrate can be mixed into the electrolyte. Since the products generated by nitrogen dioxide (NO2) in the redox reaction are mostly nitrate ions, the presence of nitrate will affect the dynamic balance in the redox reaction, thereby inhibiting the reaction of nitrogen dioxide (NO2). The reaction of the interfering gas on the electrode is further reduced to achieve the purpose of enhancing the accuracy of the electrochemical sensor.

[0042] In one embodiment of the present application, when the gas to be measured is sulfur dioxide and NO2 is the interfering gas, the first electrolyte can be selected from phosphoric acid or sulfuric acid, and the second electrolyte is nitric acid or nitrate. Generally, the liquid capacity of the second electrolyte needs to be lower than that of the first electrolyte. When the two electrolyte solutions are mixed, the injection sequence needs to be considered to avoid danger when the strong acid systems are mixed. For example: if sulfuric acid is mixed with nitric acid, sulfuric acid should be added to the nitric acid. This is because the density of concentrated sulfuric acid is greater than that of concentrated nitric acid. If concentrated nitric acid is poured into concentrated sulfuric acid, it will cause splashing of concentrated sulfuric acid and accidents are prone to occur. Therefore, the concentrated sulfuric acid with a larger density must be slowly injected into the concentrated nitric acid with a smaller density, and stirred continuously to prevent local overheating and liquid splashing.

[0043] The mixing ratio of the first electrolyte and the second electrolyte can be 3:1, 4:1, 5:1, etc., and the present invention does not make any specific limitation.

[0044] contrast Figure 2 and Figure 3 It can be seen that the response of the interfering gas NO2 is significantly reduced after adding nitric acid or nitrate solution.

[0045] In another embodiment of the present application, when the gas to be measured is ozone and NO2 is the interfering gas, the first electrolyte may be sulfuric acid and the second electrolyte may be nitric acid. The ratio may be 3:1, 4:1, 5:1, etc.

[0046] In addition, a dust-proof film can be provided on the top of the sensor to isolate dust and other pollutants.

[0047] See also Figure 4 This is a schematic diagram of the structure of an electrochemical sensor according to another embodiment of the present application. This embodiment shows that the electrochemical sensor of the present invention has four electrodes and a left-right structure.

[0048] The four-electrode system in the present invention is a prior art. The working principle of the four-electrode system can be understood as two circuits in one sensor, and the counter electrode and the reference electrode are shared by the two circuits. The sensor is connected to the external circuit through four pins, and the four pins are respectively connected to the four electrodes inside the sensor. The electrodes inside the sensor form a current loop with the outside through ion channels.

[0049] Specifically, the electrochemical sensor includes: a shell 1, a first air inlet and a second air inlet are arranged at the top of the shell 1, a first filter and a first air permeable membrane are arranged in sequence below the first air inlet; a second filter and a second air permeable membrane are arranged in sequence below the second air inlet; a working electrode 2 is arranged below the first air permeable membrane, and an auxiliary electrode 6 is arranged below the second air permeable membrane; the working electrode 2 and the auxiliary electrode 6 are arranged on the same plane and isolated in different spaces by adding a partition; an electrolyte tank 14 is arranged below the working electrode 2 and the auxiliary electrode 6, and the counter electrode 3 and the reference electrode 4 are relatively arranged on the same plane at the bottom of the electrolyte tank 14; the electrolyte tank 14 is used to accommodate an electrolyte; the filter 12 is used to filter interfering gases and water vapor, and the gas to be measured passes through the air inlet, the filter and the air permeable membrane in sequence to reach the working electrode and the auxiliary electrode.

[0050] A first gas inlet is provided above the working electrode 2, and a second gas inlet is provided above the auxiliary electrode; the working electrode 2 and the auxiliary electrode 6 are isolated in different spaces by adding a partition, thereby preventing gas mixing or mutual penetration between the working electrode 2 and the auxiliary electrode 6, that is, the gas passing through the first gas inlet can only reach the working electrode 2, and the gas passing through the second gas inlet can only reach the auxiliary electrode 6. The auxiliary electrode 6 has the same characteristics as the working electrode 2.

[0051] It should be noted that the working electrode, auxiliary electrode, reference electrode and counter electrode are all gas diffusion electrodes, which may also include a small amount of binder, and those skilled in the art may add it in appropriate amounts based on actual experience.

[0052] The auxiliary electrode 6 is used to offset the response of the working electrode to the ambient temperature, humidity, pressure and other interfering gases; the main components and manufacturing process of the auxiliary electrode are the same as those of the working electrode, and the characteristics of the auxiliary electrode 6 include its response to temperature, humidity, pressure and coexisting gases in the environment. The consistency of the characteristics of the auxiliary electrode 6 and the working electrode 2 means that under the same environment and at the same time, the output value deviation of the auxiliary electrode 6 and the working electrode 2 is less than 5%, preferably less than 1%, and most preferably less than 0.1%.

[0053] The functions and compositions of other components are consistent with those of the three-electrode system and will not be described in detail here.

[0054] The electrochemical sensor of the present invention may also have a bias voltage, which is a prior art and will not be described in detail here.

[0055] The present invention also provides a method for applying the electrochemical sensor to measure vehicle exhaust, battery bulging leakage, and gas detection during the production and waste treatment of lithium-ion batteries.

[0056] In order to improve the accuracy of the electrochemical sensor, the present invention adds a second electrolyte that matches the interfering gas to the electrolyte to effectively inhibit the chemical reaction of the interfering gas, so that only the redox reaction of the gas to be measured occurs on the electrode as much as possible, thereby achieving the purpose of enhancing the accuracy of the sensor.

[0057] It should be noted that the embodiments of the present invention have better practicability and do not impose any form of limitation on the present invention. Any technician familiar with the field may use the technical content disclosed above to change or modify it into an equivalent effective embodiment. However, any modification or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. An electrochemical sensor, characterized in that include: A plurality of electrodes in ion conduction are formed by an electrolyte, the plurality of electrodes include a working electrode, a reference electrode and a counter electrode, and the electrolyte includes a first electrolyte and a second electrolyte.

2. The electrochemical sensor according to claim 1, characterized in that The first electrolyte is sulfuric acid or phosphoric acid, and the second electrolyte is nitric acid or a nitrate solution.

3. The electrochemical sensor according to claim 2, characterized in that The liquid capacity of the second electrolyte is lower than that of the first electrolyte.

4. The electrochemical sensor according to claim 3, characterized in that The mixing volume ratio of the first electrolyte to the second electrolyte is 3:1 or 4:1 or 5:

1.

5. The electrochemical sensor according to any one of claims 1 to 4, characterized in that: The electrochemical sensor further comprises: a shell, an air inlet is arranged on the top surface of the shell, and a plurality of pins are arranged on the bottom outer surface of the shell, wherein the plurality of pins are respectively connected to the plurality of electrodes for conducting with an external circuit.

6. The electrochemical sensor according to claim 5, characterized in that A filter, a breathable membrane, a working electrode, an electrolyte tank, a counter electrode and a reference electrode are arranged in sequence from top to bottom in the shell; the counter electrode and the reference electrode are relatively arranged on the same plane at the bottom of the electrolyte tank, and the electrolyte tank is used to contain the electrolyte; the filter is used to filter interfering gases and water vapor, and the gas to be measured reaches the working electrode after passing through the air inlet, the filter and the breathable membrane in sequence.

7. The electrochemical sensor according to claim 5, characterized in that A first air inlet hole and a second air inlet hole are arranged at the top of the shell, a first filter and a first air permeable membrane are arranged in sequence below the first air inlet hole; a second filter and a second air permeable membrane are arranged in sequence below the second air inlet hole; A working electrode is disposed below the first gas permeable membrane, and an auxiliary electrode is disposed below the second gas permeable membrane; The working electrode and the auxiliary electrode are arranged on the same plane and separated into different spaces by a partition; An electrolyte tank is arranged below the working electrode and the auxiliary electrode, and the counter electrode and the reference electrode are arranged relatively on the same plane at the bottom of the electrolyte tank; the filter is used to filter interfering gases and water vapor, and the gas passing through the first air inlet can only reach the working electrode, while the gas passing through the second air inlet can only reach the auxiliary electrode, and the auxiliary electrode has the same characteristics as the working electrode.

8. The electrochemical sensor according to claim 1, characterized in that The working electrode was a platinum-carbon electrode, the counter electrode was a platinum electrode, and the reference electrode was a silver chloride electrode.

9. An electrochemical sensor for detecting vehicle exhaust, characterized in that: The electrochemical sensor described in any one of claims 1 to 8 is applied to measuring vehicle exhaust, battery bulging leakage, and gas detection during the production and waste treatment of lithium-ion batteries.

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