Platinum-carbon electrode, preparation method thereof and oxygen pump type oxygen sensor

Abstract

The invention belongs to the technical field of oxygen sensors, and provides a platinum-carbon electrode, a preparation method thereof and an oxygen pump type oxygen sensor. According to the platinum-carbon electrode provided by the invention, platinum-carbon, platinum group metal and / or platinum group metal oxide and polymer emulsion are adopted as main raw material components, the polymer emulsion contains chitosan, a cross-linking agent and a first adhesive, platinum-carbon comprises metal platinum and graphite, the chitosan is cross-linked under the action of the cross-linking agent, and the first adhesive is added into the platinum-carbon electrode; the platinum-carbon composite material can be well combined with the first adhesive, so that the capacity of adsorbing platinum group metals and / or platinum group metal oxides is improved, platinum-carbon and the platinum group metals and / or platinum group metals can be better combined together, the catalytic reaction effect is improved, the reaction current is stabilized, the linearity is enhanced, and the service life of the platinum-carbon composite material is prolonged. Furthermore, the platinum-carbon electrode is used for assembling an oxygen pump type oxygen sensor, high sensitivity is achieved, and an output current signal within the oxygen concentration range of 0-100% and the corresponding oxygen concentration have a good linear relation.

Description

Technical Field

[0001] The present invention relates to the technical field of oxygen sensors, and more specifically, to a platinum-carbon electrode and a preparation method thereof, and an oxygen pump type oxygen sensor. Background Art

[0002] Electrochemical oxygen pump oxygen sensors use electrochemical reactions to detect oxygen. This type of oxygen sensor has the advantages of high sensitivity, wide measurement range, fast response speed, and high reliability. It is widely used in industrial, medical, biological and military fields. Since lead-containing primary battery oxygen sensors cannot meet the RoHS standard (Directive on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment), their application is subject to certain restrictions. Therefore, oxygen pump / constant potential electrolytic oxygen pump oxygen sensor (Oxygen Pump Technology / Constant Potential Electrolytic Oxygen Sensor, or oxygen pump oxygen sensor) and other lead-free non-consumable oxygen pump oxygen sensors came into being. Non-consumable lead-free oxygen pump oxygen sensors are mostly platinum catalyst electrodes, using acidic electrolytes, and the working electrode is biased at -600mV relative to the reference electrode. Its working principle is: based on electrochemical reactions, the diffusion rate of oxygen is controlled by a micro capillary pump or an oxygen permeable membrane, and enters the sensor. Under the action of the catalytic layer, a catalytic reaction occurs to generate current. The magnitude of this current is proportional to the oxygen concentration, thereby detecting the oxygen concentration. The electrochemical reaction processes involved are: Working electrode: O2+4H + +4e - =2H2O Counter electrode: 2H2O =O2+4H + +4e - From the above electrochemical reaction process, the electrodes and electrolytes are not consumed, and there is no accumulation of reactants inside the sensor. Therefore, in principle, this type of sensor has a long service life, generally more than 5 years, and more stable performance. The response time will not be longer or the sensitivity will be reduced with the increase of use time. In addition, this type of non-consumable lead-free oxygen pump oxygen sensor has good low-temperature performance, avoids the use of lead, and can meet RoHS standards. However, the oxygen concentration range detected by this oxygen pump oxygen sensor is only about 0-25%. Beyond this range, the output current signal is not linearly related to the corresponding oxygen concentration, resulting in the inability to detect high concentrations of oxygen.

[0003] Therefore, there is an urgent need to develop an oxygen pump type oxygen sensor that can ensure high electrode catalytic activity while having a good linear relationship between the output current signal and the corresponding oxygen concentration when detecting 0-100% oxygen concentration, that is, taking into account both sensitivity and linearity. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a platinum-carbon electrode and a preparation method thereof, and an oxygen pump type lead-free oxygen pump type oxygen sensor. The platinum-carbon electrode provided by the present invention not only improves the sensitivity to oxygen by adjusting the formula, but also further uses the platinum-carbon electrode to assemble the oxygen pump type oxygen sensor, and the output current signal when detecting 0-100% oxygen concentration has a good linear relationship with the corresponding oxygen concentration, which can take into account both sensitivity and linearity.

[0005] A first aspect of the present invention provides a platinum-carbon electrode.

[0006] Specifically, a platinum-carbon electrode includes the following raw material components: platinum-carbon, platinum-group metals and / or platinum-group metal oxides, and polymer emulsion. The platinum-carbon includes metallic platinum and graphite, and the polymer emulsion contains chitosan, a cross-linking agent, and a first adhesive.

[0007] The cathode of the oxygen pump type oxygen sensor undergoes oxygen evolution reaction (OER). Platinum group metals and / or platinum group metal oxides are the main catalytic active components of the electrode and have catalytic activity for the electrode oxygen evolution reaction. However, platinum group metals and / or platinum group metal oxides (especially Ru or RuO2) are difficult to stably combine with platinum carbon, which easily leads to unstable performance of the oxygen pump type oxygen sensor and affects linearity. Therefore, the present invention adds chitosan and a cross-linking agent to the platinum carbon electrode. Although chitosan itself is insoluble in water, under the action of the cross-linking agent, the hydrophilicity and hydrophobicity of chitosan also change after the cross-linking reaction of chitosan. The cross-linked chitosan can be well combined with the first adhesive, thereby improving the ability to adsorb platinum group metals and / or platinum group metal oxides, so that platinum carbon and platinum group metals and / or platinum group metals can be better combined, which plays an effect of improving the catalytic oxygen evolution reaction and stabilizing the reaction current. Therefore, loading platinum group metals and / or platinum group metal oxides, chitosan, a cross-linking agent, and a first adhesive on a platinum carbon electrode can enhance the electrode OER catalytic effect, improve the electrode sensitivity, and the overall linearity of the platinum carbon electrode is high, and the output current signal in the range of 0-100% oxygen concentration has a good linear relationship with the corresponding oxygen concentration. In addition, the first adhesive helps to improve the chemical stability of the electrode and plays a role in proton conduction.

[0008] Preferably, the platinum-carbon electrode comprises the following raw material components in parts by mass: Platinum carbon 20-90 parts, Platinum group metals and / or platinum group metal oxides 1-10 servings 1-20 parts of polymer emulsion.

[0009] Further preferably, the platinum-carbon electrode comprises the following raw material components in parts by mass: 75-80 parts of platinum carbon, 2-4 parts of platinum group metals and / or platinum group metal oxides, 18-20 parts of polymer emulsion.

[0010] Preferably, the platinum group metal is at least one of Ru (ruthenium), iridium (Ir), and palladium (Pd).

[0011] Preferably, the platinum group metal oxide is at least one of RuO2, IrO2, and PdO.

[0012] Preferably, in terms of mass percentage, the polymer emulsion contains 1-10 wt % chitosan, 1-20 wt % cross-linking agent, and 1-20 wt % first adhesive.

[0013] Further preferably, in terms of mass percentage, the polymer emulsion contains 2-5 wt % chitosan, 3-5 wt % cross-linking agent, and 5-8 wt % first adhesive.

[0014] Preferably, the cross-linking agent is at least one of an aldehyde substance, a heterocyclic compound, and an acid substance.

[0015] Preferably, the aldehyde substance is glutaraldehyde and / or glyoxal.

[0016] Preferably, the heterocyclic compound is epichlorohydrin.

[0017] Preferably, the acid substance is a polycarboxylic acid.

[0018] Preferably, the first adhesive is perfluorosulfonic acid resin (PFSA) and / or polytetrafluoroethylene emulsion (PTFE).

[0019] Preferably, the polymer emulsion further contains a solvent, and the solvent is ethylene glycol and / or glycerol.

[0020] Preferably, the mass fraction of metallic platinum in the platinum-carbon is 50-70%.

[0021] Further preferably, the mass fraction of metallic platinum in the platinum carbon is 60-65%.

[0022] A second aspect of the present invention provides a method for preparing a platinum-carbon electrode.

[0023] A method for preparing a platinum-carbon electrode comprises the following steps: (1) firstly mixing chitosan, a cross-linking agent and a first adhesive to prepare a polymer emulsion; (2) In a protective gas atmosphere, platinum carbon, platinum group metals and / or platinum group metal oxides, and the polymer emulsion obtained in step (1) are mixed and hot-pressed to obtain the platinum carbon electrode.

[0024] Preferably, in step (1), chitosan and a cross-linking agent are first dissolved in a solvent, and then the first adhesive is added and mixed evenly to prepare a polymer emulsion.

[0025] Preferably, in step (2), the temperature of the hot pressing is 150-200° C., and / or the pressure of the hot pressing is 1000-2000 psi, and / or the time of the hot pressing is 1-10 s.

[0026] Further preferably, in step (2), the temperature of the hot pressing is 180-190° C., and / or the pressure of the hot pressing is 1500-1800 psi, and / or the time of the hot pressing is 5-8 s.

[0027] Preferably, in step (2), the protective gas is nitrogen.

[0028] The third aspect of the present invention provides an application of a platinum-carbon electrode.

[0029] The invention discloses an application of a platinum-carbon electrode in the field of oxygen detection.

[0030] An oxygen pump type oxygen sensor comprises a working electrode, a reference electrode and a counter electrode, wherein the reference electrode and the counter electrode are both platinum carbon electrodes, and the working electrode is a platinum black electrode.

[0031] Platinum black has a better catalytic effect on oxygen reduction than platinum carbon, and has higher sensitivity. However, electrodes with platinum black as the main raw material component generally have low linearity. The oxygen pump type provided by the present invention uses a platinum black electrode as a working electrode and a platinum carbon electrode as a counter electrode and a reference electrode. After reasonable assembly and matching, the sensitivity of the oxygen pump type oxygen sensor can be ensured, while the linearity is improved. It can detect the oxygen concentration in the full range of 0-100%, and its current output signal maintains a good linear relationship with the corresponding oxygen concentration.

[0032] Preferably, the platinum black electrode comprises the following raw material components: platinum black and a second binder.

[0033] Preferably, the mass fraction of platinum in the platinum black is greater than or equal to 99%.

[0034] Preferably, the second adhesive includes perfluorosulfonic acid resin emulsion (PFSA) and / or polytetrafluoroethylene emulsion (PTFE).

[0035] Preferably, the mass concentration of the polyperfluorosulfonic acid resin emulsion is 1-20wt%.

[0036] Preferably, the mass concentration of the polytetrafluoroethylene emulsion is 30-80wt%.

[0037] Preferably, the platinum black electrode comprises the following raw material components in terms of mass fraction: Platinum black 20-90 parts, 5-50 parts of polyperfluorosulfonic acid resin emulsion, 5-50 parts of polytetrafluoroethylene emulsion.

[0038] Preferably, the method for preparing the platinum black electrode comprises the following steps: In a protective gas atmosphere, various raw material components are mixed and hot-pressed to obtain the platinum black electrode.

[0039] Preferably, the temperature of the hot pressing is 150-200° C., the pressure of the hot pressing is 1000-2000 psi, and the time of the hot pressing is 1-10 s.

[0040] More preferably, the temperature of the hot pressing is 180-190° C., the pressure of the hot pressing is 1500-1800 psi, and the time of the hot pressing is 5-8 s.

[0041] Preferably, the protective gas is nitrogen.

[0042] A device comprises the oxygen pump type oxygen sensor, wherein the device comprises at least one of a ventilator, an incubator, an incubator, a coal mine gas detection device, an oxygen detection device, and an exhaust gas detection device.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows: The platinum-carbon electrode provided by the present invention adopts platinum carbon, platinum group metals and / or platinum group metal oxides, and polymer emulsion as main raw material components, wherein the polymer emulsion contains chitosan, a cross-linking agent, and a first adhesive, and the platinum carbon includes metal platinum and graphite. Chitosan is cross-linked under the action of the cross-linking agent and can be well combined with the first adhesive, thereby improving the ability to adsorb platinum group metals and / or platinum group metal oxides, so that platinum carbon and platinum group metals and / or platinum group metals can be better combined together, the catalytic reaction effect is improved, the reaction current is stabilized, and the linearity is enhanced. The platinum-carbon electrode of the present invention is further used to assemble an oxygen pump type oxygen sensor, which not only has high sensitivity, but also has a good linear relationship between the output current signal and the corresponding oxygen concentration in the oxygen concentration range of 0-100%. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1This is a structural explosion diagram of an oxygen pump type oxygen sensor prepared in Application Example 1 of the present invention; Figure 2 This is an output current signal diagram of the oxygen pump type oxygen sensor made in Application Example 1 of the present invention when testing 0-100% oxygen concentration; Figure 3 This is an output current signal diagram of the oxygen pump type oxygen sensor made in Application Example 1 of the present invention when testing an oxygen concentration of 0-21%; Figure 4 This is an output current signal diagram of the oxygen pump type oxygen sensor made in Application Example 2 of the present invention when testing 0-100% oxygen concentration; Figure 5 This is an output current signal diagram of the oxygen pump type oxygen sensor made in Application Example 2 of the present invention when testing an oxygen concentration of 0-21%; Figure 6 This is a graph showing the output current signal of the DD-scientific S+4OXLF oxygen pump oxygen sensor of Comparative Example 1 when testing the oxygen concentration of 0-100%; Figure 7 This is a graph showing the output current signal of the oxygen pump type oxygen sensor prepared in Comparative Example 2 when testing the oxygen concentration of 0-100%; Figure 8 This is an output current signal diagram of the oxygen pump type oxygen sensor prepared in Comparative Example 2 for testing an oxygen concentration of 0-21%; Fig. 9 This is a graph of the output current signal of the oxygen pump type oxygen sensor prepared in Comparative Example 3 when testing the oxygen concentration of 0-100%. Implementation

[0045] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0046] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods. Example

[0047] A platinum-carbon electrode, comprising the following raw material components by weight: 80 parts of platinum carbon, RuO2 2 parts, 18 parts of polymer emulsion; Platinum carbon includes metal platinum and graphite, wherein the mass content of metal platinum is 60%; In terms of mass percentage, the polymer emulsion includes: Chitosan 2wt%, Cross-linking agent glutaraldehyde 3wt%, The first adhesive PFSA 5wt%, Solvent glycol balance.

[0048] A method for preparing a platinum-carbon electrode comprises the following steps: (1) dissolving chitosan and a cross-linking agent, glutaraldehyde, in ethylene glycol, and then adding a first adhesive, PFSA, and mixing them evenly to prepare a polymer emulsion; (2) In a glove box filled with nitrogen, the polymer emulsion, platinum carbon and RuO2 were mixed evenly and hot-pressed at 180°C, with a pressure of 1500 psi for 5 seconds to obtain a platinum carbon electrode. Example

[0049] This embodiment provides a platinum-carbon electrode, which differs from Embodiment 1 in that RuO2 is replaced by an equal mass portion of IrO2.

[0050] This comparative example provides a platinum-carbon electrode, which is different from Example 1 in that the polymer emulsion does not contain chitosan and cross-linking agent.

[0051] Assembling an oxygen pump type oxygen sensor: The platinum carbon electrode prepared in Example 1 is used as the counter electrode, the reference electrode and the counter electrode are kept consistent, and the platinum black electrode is used as the working electrode to assemble an oxygen pump type oxygen sensor, the structure of which is as follows: Figure 1 As shown, from top to bottom, it includes an upper cover, a capillary, a sealing ring, a working electrode, a glass fiber diaphragm, a counter electrode, and a shell.

[0052] The method for preparing the above-mentioned platinum black electrode comprises the following steps: In a glove box filled with nitrogen, 70 parts of platinum black (containing platinum with a mass content of more than 99%), 20 parts of PFSA emulsion with a mass concentration of 5wt% and 10 parts of PTFE emulsion with a mass concentration of 60wt% were mixed evenly and then prepared into sheets by hot pressing (180°C, pressure 1500psi, time 5s) to obtain a platinum black electrode.

[0053] This application example provides an oxygen pump type oxygen sensor, which differs from application example 1 in that both the reference electrode and the counter electrode are replaced with the platinum carbon electrode prepared in example 2.

[0054] The commercially available British DD-scientific S+4OXLF oxygen pump type oxygen sensor was used.

[0055] An oxygen pump type oxygen sensor is assembled in the manner of Application Example 1, except that the working electrode, the reference electrode and the counter electrode are all platinum black electrodes.

[0056] An oxygen pump type oxygen sensor was assembled in the manner of Application Example 1, except that the reference electrode and the counter electrode were replaced with the platinum carbon electrode prepared in Comparative Example 1.

[0057] The above oxygen pump oxygen sensors were tested with oxygen concentrations of 0-100%, and the results were as follows Figure 2-9 shown.

[0058] Depend on Figure 2 and Figure 3 It can be seen that the output current value of the oxygen pump type oxygen sensor provided in Application Example 1 has always shown a good linear relationship with the corresponding test oxygen concentration. This shows that the oxygen pump type oxygen sensor provided by the present invention effectively solves the problem of decreased linearity when detecting high-concentration oxygen, and ensures high sensitivity while ensuring that the sensor as a whole has good linearity.

[0059] Depend on Figure 4 and Figure 5 It can be seen that the effect of the oxygen pump type oxygen sensor provided in Application Example 2 is equivalent to that of Application Example 1, and it is also possible to optimize the linearity of the oxygen pump type oxygen sensor while ensuring high sensitivity.

[0060] Depend on Figure 6 It can be seen that the S+4OXLF oxygen pump type oxygen sensor provided in Application Comparative Example 1 is a relatively mature lead-free oxygen pump type oxygen sensor on the market. When testing lower concentrations of oxygen in the range of 0-21%, the linearity is good, but with the increase of oxygen concentration, the output current signal does not increase linearly, but with the increase of oxygen concentration, the current signal increases in a quasi-exponential trend, indicating that the sensitivity of the oxygen pump type oxygen sensor increases with the increase of oxygen concentration, and the current signal and oxygen concentration are not linearly related.

[0061] Depend on Figure 7 It can be seen that the linearity of the oxygen pump type oxygen sensor assembled using the all-platinum black electrode of Comparative Example 2 in the oxygen concentration range of 0-100% is significantly lower than that of Example 1, and the sensitivity increases with the increase of oxygen concentration.

[0062] Depend on Figure 8 and Fig. 9 It can be seen that the oxygen pump type oxygen sensor assembled by using comparative example 3 has a certain linearity between the output current value and the tested oxygen concentration from the range of 0-100% oxygen concentration, but from the detection results of 0-21% low concentration oxygen, the linearity is significantly reduced, and its overall linearity is not as good as that of example 1. This is because chitosan and cross-linking agent are not added to the platinum carbon electrode, and RuO2 The low degree of bonding between platinum and carbon results in low electrode catalytic activity and unstable current, which makes the linearity of oxygen pump type oxygen sensor in low oxygen concentration detection low.

Claims

1. A platinum-carbon electrode, characterized in that: The invention comprises the following raw material components: platinum carbon, platinum group metals and / or platinum group metal oxides, and polymer emulsion. The platinum carbon comprises metal platinum and graphite, and the polymer emulsion contains chitosan, a cross-linking agent and a first adhesive.

2. The platinum-carbon electrode according to claim 1, characterized in that The platinum carbon electrode comprises the following raw material components in parts by mass: Platinum carbon 20-90 parts, 1-10 parts of platinum group metals and / or platinum group metal oxides, 1-20 parts of polymer emulsion.

3. The platinum-carbon electrode according to claim 1, characterized in that Calculated by mass percentage, the polymer emulsion contains 1-10wt% chitosan, 1-20wt% cross-linking agent, and 1-20wt% first adhesive.

4. The platinum-carbon electrode according to claim 1, characterized in that The cross-linking agent is at least one of an aldehyde substance, a heterocyclic compound, and an acid substance.

5. The method for preparing a platinum-carbon electrode according to any one of claims 1 to 4, characterized in that: The steps include: (1) mixing chitosan, a cross-linking agent and a first adhesive to prepare a polymer emulsion; (2) In a protective gas atmosphere, platinum carbon, platinum group metals and / or platinum group metal oxides, and the polymer emulsion obtained in step (1) are mixed and hot-pressed to obtain the platinum carbon electrode.

6. The preparation method according to claim 5, characterized in that: In step (2), the temperature of the hot pressing is 150-200° C., and / or the pressure of the hot pressing is 1000-2000 psi, and / or the time of the hot pressing is 1-10 s.

7. Application of the platinum-carbon electrode according to any one of claims 1 to 4 in the field of oxygen detection.

8. An oxygen pump type oxygen sensor, characterized in that: It comprises a working electrode, a reference electrode and a counter electrode, wherein the reference electrode and the counter electrode are the platinum-carbon electrodes according to any one of claims 1 to 4, and the working electrode is a platinum black electrode.

9. The oxygen pump type oxygen sensor according to claim 8, characterized in that: The platinum black electrode includes the following raw material components: platinum black and a second binder.

10. A device, characterized in that: Including the oxygen pump type oxygen sensor according to claim 8 or 9, the equipment includes at least one of a ventilator, an incubator, an incubator, a coal mine gas detection equipment, an oxygen detection equipment, and an exhaust gas detection equipment.

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