CN113567523A - Device and method for measuring pH value of electrode solution interface - Google Patents
Device and method for measuring pH value of electrode solution interface Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/416—Systems
- G01N27/4166—Systems measuring a particular property of an electrolyte
- G01N27/4167—Systems measuring a particular property of an electrolyte pH
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/302—Electrodes, e.g. test electrodes; Half-cells pH sensitive, e.g. quinhydron, antimony or hydrogen electrodes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
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Abstract
The invention relates to the field of metal corrosion, in particular to a device and a method for measuring the pH value of an electrode solution interface. The device comprises an electrolytic cell chamber A (8), an electrolytic cell chamber B (12), a glass salt bridge (6), a saturated calomel electrode (7), a proton exchange membrane (9), a platinum wire (11) and IrOxA microelectrode (28) and an insulated hollow screw (29), wherein one end of the insulated hollow screw (29) is provided with IrOxA microelectrode (28) for implementing said IrO by screwing an insulated hollow screw (29)xThe distance between the microelectrode (28) and the electrode sample (3). Recording IrO under non-polarized or polarized conditionsxAnd the potential data of the microelectrode (28) is converted according to the Nernst equation to obtain the pH value of the interface of the medium solution to be detected. The invention is provided withThe device is simple in structure and convenient to operate, and can meet the requirement of pH measurement in micro areas of the metal electrode near-interface solution to be measured under different polarization conditions.
Description
Technical Field
The invention relates to a device for researching interface pH in the field of metal corrosion, in particular to a device and a method for measuring the interface pH of an electrode solution.
Background
The corrosion of metals in aqueous solutions is closely related to the interfacial pH of the metal solution, and most of the factors affecting metal corrosion are usually processes that act on metal corrosion by changing the interfacial pH, such as pressure, biofouling, solution flow rate, and the like. In particular, in order to inhibit corrosion of metals, the most common and effective method in practical corrosion prevention works is cathodic protection, in which anodic reactions of metal dissolution are attenuated by applying a cathodic polarization potential or a polarization current to the metal. During the cathodic protection application process, a great amount of OH can be caused due to the occurrence of oxygen absorption reaction and hydrogen evolution reaction-The generation of the metal surface can cause drastic change of the interfacial pH of the metal solution, and the change of the interfacial pH can generate other additional effects, such as generation of calcium and magnesium deposits on the metal surface in seawater solution, influence of the excessive interfacial pH on the attachment and survival of microorganisms on the metal surface, and the like. Therefore, the measurement of the metal solution interface pH under the polarization condition is helpful for further researching the mechanism of the influence of the interface pH on the corrosion process under the polarization condition.
However, since the apparent change of the pH of the metal solution interface under polarization conditions occurs only in a small region near the interface, the existing glass pH electrodes have no measurement capability due to their large size, and thus the use of minute metal oxide electrodes as pH sensors has been widely studied. The method mainly comprises two modes in the practical application of the current metal oxide electrode in measuring the pH value of an interface, wherein one mode is that the metal oxide electrode is originally arranged around the metal electrode to be measured, the metal electrode and the oxide electrode are isolated by adopting a glass tube, and the distance between the metal electrode and the metal oxide electrode is controlled by the thickness of the wall of the glass tube; and secondly, the metal oxide electrode and the measured metal electrode are placed in a close distance by controlling the shapes of the metal oxide electrode and the measured metal electrode, and the method has special requirements on the shape of the measured metal electrode and is not suitable for large-scale application. Therefore, an apparatus which is easy and convenient to operate and easy to control is urgently needed to explore the change of the pH of the interface.
Disclosure of Invention
The invention aims to provide a device and a method for measuring the pH value of an electrode solution interface.
In order to achieve the purpose, the invention adopts the technical scheme that:
a device for measuring the pH value of an electrode solution interface comprises an electrolytic cell chamber A (8), an electrolytic cell chamber B (12), a glass salt bridge (6), a saturated calomel electrode (7), a proton exchange membrane (9), platinum wires (11) and IrOxA microelectrode (28) and an insulating hollow screw (29), wherein two ends of an electrolytic cell cavity A (8) are respectively provided with a clamp A (5) and a clamp B (13), and two ends of the electrolytic cell cavity A (8) are respectively in sealing and abutting joint with the clamp A (5) and the clamp B (13); the two ends of the electrolytic cell cavity B (12) are respectively provided with a clamp C (14) and a clamp D (30), the two ends of the electrolytic cell cavity B (12) are respectively in sealing butt joint with the clamp C (14) and the clamp D (30), and the clamp A (5), the clamp B (13), the clamp C (14) and the clamp D (30) are fixedly connected through a fixing device; the clamp A (5), the clamp B (13) and the clamp C (14) are respectively provided with a channel for solution to flow, and the electrode sample (3) is arranged at the front channel of the clamp A (5) and is fixed through an elastic pressing sheet (17) hinged on the front of the clamp A (5); a proton exchange membrane (9) is arranged between the channel on the clamp B (13) and the channel on the clamp C (14); a glass salt bridge (6) with a robust capillary tube is inserted at the top end of the electrolytic cell cavity A (8), a saturated calomel electrode (7) is inserted at the top end of the glass salt bridge (6), and a platinum wire auxiliary electrode (10) is inserted at the top end of the electrolytic cell cavity B (12); threaded holes are formed in the clamp B (13), the clamp C (14) and the clamp D (30), the insulating hollow screw (29) is in threaded connection with the threaded holes respectively, and IrO is mounted at one end of the insulating hollow screw (29)xAnd the microelectrode (28) realizes the distance between the IrOx microelectrode (28) and the electrode sample (3) by screwing the insulated hollow screw (29).
The reverse side of the clamp A (5) is provided with a groove A (16) which is in sealing and abutting joint with the electrolytic cell cavity A (8), and through holes A (15) for connecting a fixing device are arranged around the clamp A (5); the front center of the clamp A (5) is provided with a channel A (19) for solution to flow through, and a groove B (18) for placing a rubber gasket is arranged around the channel A (19).
The front of anchor clamps B (13) sets up recess C (23) and the screw hole A (22) that are used for insulating cavity screw rod (29) to run through and threaded connection with electrolytic cell cavity A (8) sealed butt, the reverse side of anchor clamps B (13) sets up passageway B (24) that supplies the solution circulation, and the periphery of this passageway B (24) sets up recess D (21) of placing the rubber packing ring, set up through-hole B (20) that supply fixing device to connect around anchor clamps B (13).
The front of anchor clamps C (14) sets up recess C (23) and the screw hole A (22) that are used for insulating cavity screw rod (29) to run through and threaded connection with electrolytic bath cavity B (12) sealed butt, the reverse side of anchor clamps C (14) sets up the passageway B (24) that supplies the solution circulation, and the periphery of this passageway B (24) sets up recess D (21) of placing the rubber packing ring, set up through-hole B (20) that supply fixing device to connect around anchor clamps B (14).
The front surface of the clamp D (30) is provided with a groove E (27) which is in sealing and abutting joint with the electrolytic cell chamber B (12) and a threaded hole B (26) which is used for penetrating and in threaded connection with an insulating hollow screw rod (29), and the periphery of the clamp D (30) is provided with a through hole C (25) for connecting a fixing device.
The proton exchange membrane (9) arranged between the clamp B (13) and the clamp C (14) is used for isolating H between the electrolytic cell chamber A (8) and the electrolytic cell chamber B (12)+The other materials circulate.
The other end of the insulated hollow screw (29) is positioned outside the clamp D (30).
The fixing device comprises a screw rod (1) and a nut (2), the screw rod (1) penetrates through the clamp A (5), the clamp B (13), the clamp C (14) and the clamp D (30) respectively, and two ends of the screw rod (1) are screwed and positioned through the nut (2) respectively.
The method for measuring the pH value of the interface of the electrode solution by using the device adjusts the electrode sample (3) and the IrO according to the devicexThe distance between the microelectrodes (28) is used for respectively injecting the medium solution to be measured into the electrolytic cell cavity A (8) and the electrolytic cell cavityB (12) recording IrO under non-polarized or polarized conditionsxAnd the potential data of the microelectrode (28) is converted according to the Nernst equation to obtain the interface pH value of the medium solution to be detected.
The polarization condition is to apply a polarization potential or a polarization current to the electrode sample (3).
The pH value of the medium solution to be detected is 2-12, and preferably 4-10.
The electrode sample (3) is selected from any metal.
The method is suitable for measuring the electrode solution interface pH value under the non-polarization condition, and is preferably suitable for measuring the electrode solution interface pH value under various polarization conditions.
IrOxMicroelectrode (28) pair H+Sensitivity, the principle of its response to pH is as follows:
2IrOx+2H++2e-＝Ir2O3+H2O
by IrOxAnd H+The reaction between (a) and (b) can yield the following ideal nernst equation:
E＝Eθ–2.303RT/nFpH
wherein E isθIs the standard electrode potential of an iridium oxide electrode, R is the gas constant, T is the temperature, F is the Faraday constant, n is the reaction electron transfer number, and the value of RT/F at room temperature is a constant equal to about 25.69.
Compared with the prior art, the invention has the following advantages:
1. the device for measuring the pH value of the electrode solution interface is formed by combining a plurality of components, wherein the electrolytic cell and the clamp are both made of high-transparency acrylic glass, so that IrO (iridium oxide) can be observed convenientlyxDistance of the microelectrode tip from the electrode surface. The electrolytic cell comprises two chambers, the substance transfer between the two chambers is realized through a proton exchange membrane, the interference of reaction products of an auxiliary electrode on the pH measurement of the surface of a measured electrode during cathode polarization is avoided, and the requirement on the pH measurement in a micro area of a near-interface solution of the measured metal electrode under a non-polarization condition, especially under different polarization conditions, can be realized.
2. The inventionThe electrochemical system of the device is simple in structure and comprises two electrochemical systems, wherein one electrochemical system is a polarization system for polarizing an electrode sample, and the other electrochemical system is used for IrOxA microelectrode potential measuring system, wherein a saturated calomel electrode 7 is used as a reference electrode, and IrOxThe microelectrode 28 is a working electrode to form a potential measuring system, the platinum wire 11 is used as an auxiliary electrode, the saturated calomel electrode 7 is used as a reference electrode, the metal electrode 3 is used as a working electrode to form a polarization system, the device is suitable for measuring the pH between a medium solution and a metal electrode interface under different polarization conditions, can realize the real-time monitoring of the pH of the electrode solution interface and the accurate determination of the pH value, and further researches the influence of different polarization conditions on the change of the pH of the electrode solution interface.
3. The invention solves the problem of narrow and small interface pH measuring area by using the small-sized metal oxide electrode, simultaneously avoids the disturbance of overlarge pH probe to the transmission of the material near the interface of the measured metal electrode, solves the limitation of the shape of the measured metal electrode formed by controlling the distance between the measured metal electrode and the measured metal electrode by a method of native metal oxide electrode around the measured metal electrode in the prior art, and solves the problem that the metal oxide electrode can not be repeatedly used; secondly, compared with the prior art, the device controls the distance between the pH sensor and the measured metal electrode through the threaded rod, and provides a feasible scheme for solving the problem of measuring the interface pH under the polarization condition by using a low-cost combined device.
Drawings
FIG. 1A is a schematic structural diagram of an apparatus for measuring the pH of an electrode solution interface under polarization conditions provided by the present invention;
FIG. 1B is a schematic structural view of the fixture A indicated by reference numeral 5 in FIG. 1A;
FIG. 1C is a schematic view of the structure of the clamp B and the clamp C indicated by the reference numerals 13 and 14 in FIG. 1A;
FIG. 1D is a schematic view of the fixture D indicated by reference numeral 30 in FIG. 1A;
FIG. 1E shows IrO according to the present inventionxA schematic structure diagram of a microelectrode and an insulated hollow screw;
in FIGS. 1A-1E: 1 is screw, 2 is nut, 3 is electrode testIn the specification, 4 is a rubber gasket A, 5 is a clamp A, 6 is a glass salt bridge, 7 is a saturated calomel electrode, 8 is an electrolytic cell chamber A, 9 is a proton exchange membrane, 10 is a rubber gasket B, 11 is a platinum wire, 12 is an electrolytic cell chamber B, 13 is a clamp B, 14 is a clamp C, 15 is a through hole A, 16 is a groove A, 17 is an elastic pressing sheet, 18 is a groove B, 19 is a channel A, 20 is a through hole B, 21 is a groove D, 22 is a threaded hole A, 23 is a groove C, 24 is a channel B, 25 is a through hole C, 26 is a threaded hole B, 27 is a groove E, 28 is IrOxA microelectrode 29 is an insulating hollow screw rod, and a clamp D30 is arranged;
FIG. 2 shows the Nernst slope calibration process of the IrOx microelectrode of example 2 for IrOxxThe relationship between the microelectrode potential and the solution pH;
FIG. 3 is IrO of example 2xIrO in process of determining standard electrode potential of microelectrodexThe potential of the micro-electrode in the artificial seawater;
FIG. 4 shows the IrO near the interface solution of the metal electrode to be tested under-0.9V (vs. SCE) polarization potential in example 2xThe potential of the microelectrode changes with time and the corresponding pH value;
FIG. 5 shows the IrO near the interface solution of the metal electrode to be tested under-0.8V (vs. SCE) polarization potential in example 3xMicroelectrode potential changes with time and the corresponding change in pH.
Detailed Description
The invention will be further illustrated with reference to the following specific examples.
It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, it should be understood that various changes or modifications can be made by those skilled in the art after reading the disclosure of the present invention, and such equivalents also fall within the scope of the invention.
Example 1
The device for measuring the pH value of the electrode solution interface is shown in figures 1A-1E and comprises an electrolytic cell chamber A8, an electrolytic cell chamber B12, a glass salt bridge 6, a saturated calomel electrode 7, a proton exchange membrane 9, a platinum wire 11, an IrOx microelectrode 28 and an insulated hollow screw 29, wherein two ends of the electrolytic cell chamber A8 are respectively provided with a clamp A5 and a clamp B13, and the electrolytic cell chamber A8 is provided with a clamp A5 and a clamp B13Two ends of the pool chamber A8 are respectively in sealing and abutting joint with a clamp A5 and a clamp B13; the two ends of the electrolytic cell chamber B12 are respectively provided with a clamp C14 and a clamp D30, the two ends of the electrolytic cell chamber B12 are respectively in sealing and abutting joint with a clamp C14 and a clamp D30, and the clamp A5, the clamp B13, the clamp C14 and the clamp D30 are fixedly connected through a fixing device; the clamp A5, the clamp B13 and the clamp C14 are all provided with a channel for solution to flow through, and the electrode sample 3 is arranged at the front channel of the clamp A5 and is fixed by an elastic pressing sheet 17 hinged on the front of the clamp A5; a proton exchange membrane 9 is arranged between the channel on the clamp B13 and the channel on the clamp C14, and the proton exchange membrane 9 is used for isolating H between the electrolytic cell chamber A8 and the electrolytic cell chamber B12+The circulation of other substances; the fixture B13, the fixture C14 and the fixture D30 are all provided with threaded holes, the insulating hollow screw 29 is respectively in threaded connection with the threaded holes, one end of the insulating hollow screw 29 is provided with the IrOx microelectrode 28, the other end of the insulating hollow screw 29 is positioned outside the fixture D30, and the distance between the IrOx microelectrode 28 and the electrode sample 3 is realized by screwing the insulating hollow screw 29.
The back surface of the clamp A5 of the embodiment is provided with a groove A16 which is in sealing and abutting joint with the electrolytic cell chamber A8, and the periphery of the clamp A5 is provided with a through hole A15 for connecting a fixing device; the center of the front surface of the clamp A5 is provided with a channel A19 for the solution to flow through, and a groove B18 for placing a rubber gasket A4 is arranged around the channel A19.
The front surface of the clamp B13 of the embodiment is provided with a groove C23 which is in sealing contact with the electrolytic cell chamber A8 and a threaded hole A22 which is used for penetrating and threaded connection of the insulating hollow screw 29, the back surface of the clamp B13 is provided with a channel B24 for solution circulation, the periphery of the channel B24 is provided with a groove D21 for placing a rubber gasket B10, and the periphery of the clamp B13 is provided with a through hole B20 for connection of a fixing device.
The front surface of the clamp C14 of the embodiment is provided with a groove C23 which is in sealing contact with the electrolytic cell chamber B12 and a threaded hole A22 which is used for penetrating and threaded connection of the insulating hollow screw 29, the back surface of the clamp C14 is provided with a channel B24 for solution circulation, the periphery of the channel B24 is provided with a groove D21 for placing a rubber gasket B10, and the periphery of the clamp B14 is provided with a through hole B20 for connection of a fixing device.
The front surface of the clamp D30 of the present embodiment is provided with a groove E27 for sealing contact with the cell chamber B12 and a threaded hole B26 for penetrating and screwing the insulating hollow screw 29, and the periphery of the clamp D30 is provided with a through hole C25 for connecting a fixing device.
The electrolytic cell chamber A8 of this embodiment is made of high-transparency acrylic glass, and has a hole at the top for placing the glass salt bridge 6 with a Rujin capillary tube, and a saturated calomel electrode 7 is inserted at the top of the glass salt bridge 6. Both ends of the cell chamber A8 are inserted into the grooves a16 and C23 provided in the jig a5 and the jig B13, respectively.
The electrolytic cell chamber B12 of this embodiment is made of high transparency acrylic glass, and a hole is opened at the top for placing the auxiliary electrode platinum wire 11, and the two ends of the electrolytic cell chamber B12 are respectively inserted into the grooves C23 and E27 of the clamp C14 and the clamp D30.
The proton exchange membrane 9 of the embodiment is arranged between the electrolytic cell chamber 8 and the electrolytic cell chamber 12 and is used for preventing oxidizing substances, such as ClO, generated by anode reaction of the platinum wire 11 of the auxiliary electrode-Causing corrosion and interference to the metal specimen.
The fixing device of the embodiment comprises four stainless steel screws 1 and eight stainless steel nuts 2, wherein the screws 1 respectively penetrate through the clamp A5, the clamp B13, the clamp C14 and the clamp D30, and two ends of each screw 1 are respectively screwed and positioned through the nuts 2.
The four clamps of this embodiment are square boards, and the recess that is used for with the sealed butt of electrolysis trough cavity and the recess that is used for placing the rubber packing ring that offer on the anchor clamps are circular recess.
Wherein the metal electrode 3 surface and IrO are controlledxThe material of the insulated hollow screw 29 at the distance between the tips of the microelectrodes 28 is polytetrafluoroethylene.
Example 2
The method for measuring the interfacial pH of the metal electrode solution under polarization conditions by using the device is arranged according to the device, and the metal electrode is controlled by rotating the insulated hollow screw 29 with the assistance of a microscope3 surface and IrOxThe distance between the tips of the microelectrodes 28 is about 300 μm, the microelectrodes are fixed, the medium solution to be measured is respectively injected into the electrolytic cell chamber 8 and the electrolytic cell chamber 12, the saturated calomel electrode 7 is used as a reference electrode, and IrO isx Microelectrode 28 is a working electrode to form a potential measuring system, platinum wire 11 is used as an auxiliary electrode, saturated calomel electrode 7 is a reference electrode, metal electrode 3 is a working electrode to form a polarization system, a constant polarization potential of-0.9V is applied to metal electrode 3 by a potentiostat, and IrO is continuously recorded by a data recorderxAnd converting the potential data of the microelectrode by an nernst equation to obtain the pH value of the solution of the metal electrode near interface to be detected.
The medium solution to be tested in this embodiment is artificial seawater prepared according to astm d1141-98(2013) standard, and does not contain Ca2+、Mg2+Ions to prevent calcareous deposits from affecting IrOxMicro-electrode 25 having NaCl 24.53g and Na 4.09g as the main components2SO4，0.695g KCl，0.201g NaHCO3，0.101g KBr，0.027g H3BO3And after the preparation is finished, the pH value of the artificial seawater is measured to be 8.05.
In this embodiment, the metal sample 3 is a sheet sample made of a metal material AISI 4135 steel and having a diameter of 4cm and a thickness of 0.05cm, the sample is polished step by step (600#, 800#, 1000#, 1500#, 2000#), the steel sheet and the copper wire are electrically connected by soldering, then the sample is washed by deionized water, the sample is placed in acetone for ultrasonic cleaning for 5min, the sample is taken out and cleaned by absolute ethyl alcohol, and the surface is dried by cold air.
The IrOx microelectrode of the embodiment can be prepared by a carbonate heat treatment preparation method described in the prior document; the Nernst slope and the standard electrode potential of the iridium oxide electrode obtained under different preparation conditions are different, and the iridium oxide electrode needs to be used after calibration when in use, but has no influence on a device and a measurement method.
The procedure for calibrating the Nernst slope of the IrOx microelectrodes used in this example is as follows:
a series of calibrations with different pH values were prepared by dropwise addition of 0.1mol/l NaOH solution or 0.1mol/l HCl solution to a standard buffer solutionSolution, in the natural state, using IrO used in the subsequent experimentsxMethod for measuring IrO (iron oxide) in corresponding solution by using measuring system consisting of microelectrode and saturated calomel electrodexThe potential of the microelectrode is matched with the relationship between the potential data and the pH value of the solution to obtain the prepared specific IrOxNernst slope of microelectrodes. By IrOxTwo experiments carried out at the early stage and the later stage of microelectrode hydration obtain the result shown in figure 2, and the IrO is measured twicexThe Nernst slopes of the microelectrodes were substantially uniform, so that the average of the two results was taken as IrOxThe actual Nernst slope of the microelectrode was-57.01.
IrO used in this examplexThe determination process of the standard electrode potential of the microelectrode is as follows:
using IrO after complete hydrationxThe measurement system composed of microelectrode and saturated calomel electrode measures the corresponding electrode potential of artificial seawater (pH 8.05), as shown in FIG. 3, the average electrode potential in 300s is 148.68mV, and the Nernst equation E is introducedθ-57.01 pH to obtain this specific IrOxActual standard electrode potential E of microelectrodesθThe concentration was 607.61 mV.
IrO used in this example was obtained by the above measurement procedurexThe actual Nernst equation for microelectrodes is:
E＝607.61–57.01pH
a constant polarization potential of-0.9V (vs. SCE) was applied to the electrode sample (3), and IrO was continuously recorded by a data recorderxPotential data of the microelectrode (28) is converted into pH data by the Nernst equation to obtain the pH value change of the artificial seawater at the near interface of the metal electrode to be detected under the corresponding polarization condition, and IrO is under the polarization condition of-0.9V (vs. SCE)xSCE and potential (vs) of the microelectrode (28) are shown in FIG. 4.
Example 3
In this embodiment, the tested metal electrode material and the dielectric solution are the same as those in embodiment 2, except that the polarization potential applied to the tested metal electrode in this embodiment is-0.8V (vs. sce), the testing method and the procedure are the same as those in embodiment 2, and the testing result is shown in fig. 5.
As can be seen from FIGS. 4 and 5, the overall trend of the pH value variation of the interface in the continuous test for nearly 100min is that the pH value of the interface reaches quasi-steady-state pH values of 9.6 and 9.3 respectively under the polarization conditions of-0.8V and-0.9V, and thus, the more negative the polarization potential, the higher the pH value of the solution of the metal electrode to be tested near the interface is.
Example 4
The method for measuring the pH value of the metal electrode solution interface under the non-polarization condition by adopting the device is arranged according to the device, and the surface of the metal electrode 3 and the IrO are controlled by rotating the insulated hollow screw 29 with the assistance of a microscopexThe distance between the tips of the microelectrodes 28 is about 300 μm, the microelectrodes are fixed, the medium solution to be detected is respectively injected into the electrolytic cell chamber 8 and the electrolytic cell chamber 12, the saturated calomel electrode 7 is used as a reference electrode, and IrO isx Microelectrode 28 is a working electrode to form a potential measuring system, and IrO is continuously recorded by a data recorderxAnd converting the potential data of the microelectrode by an nernst equation to obtain the pH value of the solution of the metal electrode near interface to be detected.
The device and the measuring method can meet the requirement of measuring the pH of the metal electrode to be measured in micro-areas of near-interface solutions in different medium solutions under the non-polarization condition and different polarization conditions, and realize the real-time monitoring of the pH of the electrode solution interface and the accurate measurement of the pH value. Compared with the prior art, the method has the advantages of simple device design and low cost, and can obtain accurate results.
Claims (10)
1. The device for measuring the pH value of the electrode solution interface is characterized by comprising an electrolytic cell chamber A (8), an electrolytic cell chamber B (12), a glass salt bridge (6), a saturated calomel electrode (7), a proton exchange membrane (9), a platinum wire (11) and IrOxA microelectrode (28) and an insulating hollow screw (29), wherein two ends of an electrolytic cell cavity A (8) are respectively provided with a clamp A (5) and a clamp B (13), and two ends of the electrolytic cell cavity A (8) are respectively in sealing and abutting joint with the clamp A (5) and the clamp B (13); what is needed isThe two ends of the electrolytic cell cavity B (12) are respectively provided with a clamp C (14) and a clamp D (30), the two ends of the electrolytic cell cavity B (12) are respectively in sealing contact with the clamp C (14) and the clamp D (30), and the clamp A (5), the clamp B (13), the clamp C (14) and the clamp D (30) are fixedly connected through a fixing device; the clamp A (5), the clamp B (13) and the clamp C (14) are respectively provided with a channel for solution to flow, and the electrode sample (3) is arranged at the front channel of the clamp A (5) and is fixed through an elastic pressing sheet (17) hinged on the front of the clamp A (5); a proton exchange membrane (9) is arranged between the channel on the clamp B (13) and the channel on the clamp C (14); a glass salt bridge (6) with a robust capillary tube is inserted at the top end of the electrolytic cell cavity A (8), a saturated calomel electrode (7) is inserted at the top end of the glass salt bridge (6), and a platinum wire auxiliary electrode (10) is inserted at the top end of the electrolytic cell cavity B (12); threaded holes are formed in the clamp B (13), the clamp C (14) and the clamp D (30), the insulating hollow screw (29) is in threaded connection with the threaded holes respectively, and IrO is mounted at one end of the insulating hollow screw (29)xAnd the microelectrode (28) realizes the distance between the IrOx microelectrode (28) and the electrode sample (3) by screwing the insulated hollow screw (29).
2. The device for measuring the interfacial pH of the electrode solution according to claim 1, wherein the reverse side of the clamp A (5) is provided with a groove A (16) which is in sealing and abutting joint with the electrolytic cell chamber A (8), and the periphery of the clamp A (5) is provided with a through hole A (15) for connecting a fixing device; the front center of the clamp A (5) is provided with a channel A (19) for solution to flow through, and a groove B (18) for placing a rubber gasket is arranged around the channel A (19).
3. The device for measuring the electrode solution interface pH according to claim 1, characterized in that the front surface of the clamp B (13) is provided with a groove C (23) which is in sealing contact with the electrolytic cell chamber A (8) and a threaded hole A (22) for penetrating and threaded connection of an insulating hollow screw (29), the back surface of the clamp B (13) is provided with a channel B (24) for the solution to flow through, the periphery of the channel B (24) is provided with a groove D (21) for placing a rubber gasket, and the periphery of the clamp B (13) is provided with a through hole B (20) for connecting a fixing device.
4. The device for measuring the electrode solution interface pH according to claim 1, characterized in that the front surface of the clamp C (14) is provided with a groove C (23) which is in sealing contact with the electrolytic cell chamber B (12) and a threaded hole A (22) for penetrating and threaded connection of an insulating hollow screw (29), the back surface of the clamp C (14) is provided with a channel B (24) for the solution to flow through, the periphery of the channel B (24) is provided with a groove D (21) for placing a rubber gasket, and the periphery of the clamp B (14) is provided with a through hole B (20) for connecting a fixing device.
5. The device for measuring the interfacial pH of the electrode solution according to claim 1, wherein the front surface of the clamp D (30) is provided with a groove E (27) which is in sealing contact with the electrolytic cell chamber B (12) and a threaded hole B (26) for the penetration and threaded connection of an insulating hollow screw rod (29), and the periphery of the clamp D (30) is provided with a through hole C (25) for connecting a fixing device.
6. The device for measuring the pH value of the electrode solution interface according to claim 1, wherein a proton exchange membrane (9) is arranged between the clamp B (13) and the clamp C (14) and used for isolating H from the electrolytic cell chamber A (8) and the electrolytic cell chamber B (12)+The other materials circulate.
7. The apparatus for measuring the interfacial pH of an electrode solution according to claim 1, wherein the other end of the insulated hollow screw (29) is located outside the jig D (30).
8. The device for measuring the electrode solution interface pH according to claim 1, wherein the fixing device comprises a screw (1) and a nut (2), the screw (1) passes through the clamp A (5), the clamp B (13), the clamp C (14) and the clamp D (30), and two ends of the screw (1) are respectively screwed and positioned by the nut (2).
9. A method for measuring the pH of an electrode solution interface using the device according to any one of claims 1 to 8,characterized in that the electrode sample (3) and the IrO are adjusted according to the devicexThe distance between the microelectrodes (28) is determined by injecting the medium solution to be measured into the electrolytic cell chamber A (8) and the electrolytic cell chamber B (12), respectively, and recording IrO under non-polarized or polarized conditionsxAnd the potential data of the microelectrode (28) is converted according to the Nernst equation to obtain the pH value of the interface of the medium solution to be detected.
10. The method of claim 9, wherein: the polarization condition is that a polarization potential or a polarization current is applied to the electrode sample (3).
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