A method and device for detecting active area of ​​flow battery electrode

Abstract

The present invention relates to the field of detection technology, and discloses a method and device for detecting the active area of ​​a flow battery electrode. The present invention combines a potential scanning system and an optical sensor, and uses the potential scanning system and the optical sensing system to simultaneously perform in-situ detection of the electrochemical reaction of the electrode. The optical sensing system calculates the current density of the electrode by collecting the optical signal change caused by the change in the refractive index of the electrolyte, and the potential scanning system obtains the electrode current. The electrode active area is obtained by dividing the two. The present invention is easy to operate, and uses a more sensitive phase-type optical sensor combined with an electrochemical workstation to perform in-situ detection of the active area of ​​the electrode, giving the active area actually participating in the electrochemical reaction, and providing a technical tool for characterizing the active area of ​​the electrode participating in the electrochemical reaction.

Description

Technical Field

[0001] The invention relates to the field of detection technology, in particular to a method and a device for detecting the active area of ​​a liquid flow battery electrode. Background Art

[0002] Energy issues have driven people to develop clean energy and energy storage technologies, including water splitting and flow batteries. The performance improvement of these technologies involves the improvement of catalysts and electrode activity. Electrocatalysts are loaded on the surface of electrodes, changing the surface state of the electrodes, and then changing the potential and reaction rate of the reaction, so that the electrodes can select electrochemical reactions. Among them, the catalyst active area and electrode active area are one of the important factors affecting its electrochemical reaction.

[0003] According to the literature (Chem. Soc. Rev., 48, 2518 (2019)), the main methods for characterizing the active area of ​​an electrode are redox reaction method, double layer capacitance method, atomic force microscopy, electron microscopy and BET method. The redox reaction method mainly obtains all the transferred charges by dividing the transferred charge of a single active site by the area of ​​the cyclic voltammetry curve to give the active area. This method has the disadvantages that the number of transferred charges at the active site of the electrode material is unknown in the experiment and the baseline of the area integration is difficult to determine. The double layer capacitance method obtains the active area by dividing the double layer capacitance by the specific capacitance. The double layer capacitance measured by this method may change with the electrode potential and electrode composition, and is also affected by side reactions, resulting in consistency problems in the measured active area. Atomic force microscopy gives the active area of ​​the electrode by measuring the roughness of the electrode and combining it with the geometric area obtained by optical microscopy. This method is only applicable to thin film materials with relatively smooth surfaces. Electron microscopy determines its surface area by measuring the diameter of the object to be measured and idealizing its shape. This method has the disadvantages of errors in the measurement results caused by the difference between the ideal shape and the actual shape of the object to be measured. The BET method is currently the best choice for obtaining active area. It mainly relies on the physical adsorption of gas molecules on the solid surface of the material to be tested to obtain the surface area of ​​the material. It has problems such as the measured surface area is not equal to the active area actually involved in the electrochemical reaction. Therefore, all of the above methods have their own shortcomings, and it is necessary to invent a more efficient and simpler method for in-situ characterization of the active area of ​​the electrode.

[0004] The evanescent wave optical detection method is widely used in the biomedical field because of its high sensitivity, high resolution and in-situ non-destructive detection. It can detect the refractive index change at the interface in real time and measure the current density of the electrochemical reaction. We have applied for the patent "A method and device for online detection of local reaction activity of liquid flow battery electrodes" (application number 201811617909.6) and the patent "A method and device for in-situ detection of current density distribution of liquid flow battery electrodes" (application number 201910060777.X), respectively using surface plasmon resonance technology to characterize electrode activity and total reflection imaging technology to perform in-situ detection of current density distribution during battery operation. The present invention uses a more sensitive phase-type optical sensor combined with an electrochemical workstation to perform in-situ detection of the active area of ​​the electrode, giving the active area actually participating in the electrochemical reaction, and providing a technical tool for characterizing the active area of ​​the electrode participating in the electrochemical reaction. Summary of the invention

[0005] In view of the defects of the above-mentioned prior art, the present invention proposes an in-situ detection method for measuring the active area of ​​the electrode participating in the electrochemical reaction, taking the liquid flow battery electrode as an example. The electrochemical reaction of the electrode is simultaneously detected in situ by a potential scanning system and an optical sensing system. The optical sensing system calculates the current density of the electrode by collecting the optical signal changes caused by the change of the refractive index of the electrolyte, and the potential scanning system obtains the electrode current. The electrode active area is obtained by dividing the electrode current by the current density.

[0006] Furthermore, the potential scanning system performs in-situ detection of the electrochemical reaction of the electrode, specifically the electrochemical workstation drives the electrode to perform a cyclic voltammetry test, and the system of the cyclic voltammetry test is a three-electrode system.

[0007] Furthermore, the optical sensing system is a prism-coupled total reflection optical path system, preferably a prism-coupled reflective phase-type optical sensor.

[0008] Furthermore, the change in the valence state of the active substance in the electrolyte on the electrode causes a change in the refractive index, which is reflected in the change in the central wavelength of the optical sensor detection signal. The current density is obtained based on the relationship between the change in the central wavelength signal and the current density.

[0009] The above-mentioned method for detecting the active area of ​​the flow battery electrode comprises the following steps:

[0010] (1) The electrode to be tested is installed as a working electrode into a three-electrode system module and immersed in an electrolyte so that it is in close contact with the prism of the optical sensing system, and then the module is assembled into the optical path of the sensor;

[0011] (2) adjusting the reflective phase optical sensor to a total reflection state and making the optical system state within a dynamic range with the highest sensitivity, while recording the initial optical signal of the sensor;

[0012] (3) performing a cyclic voltammetry test on the electrode immersed in the electrolyte with the aid of an electrochemical workstation to obtain a cyclic voltammetry curve, extracting the oxidation or reduction peak current, and simultaneously collecting a reflected light signal that changes with time with a phase-type optical sensor, and calculating a curve of the change of the central wavelength with time from the reflected light signal;

[0013] (4) using the relationship between the central wavelength and the current density, converting the obtained central wavelength variation curve over time into a relative current density variation curve, and extracting the relative value of the oxidation or reduction peak current density;

[0014] (5) determining the relationship between the current density obtained by the electrochemical workstation and the relative current density obtained by the optical sensor by performing cyclic voltammetry tests at different potential scan rates on a uniformly tunable electrode with known area;

[0015] (6) According to the above relationship, the absolute value of the current density collected by the optical sensor during the cyclic voltammetry of the electrode to be tested is obtained, so that the oxidation or reduction peak current density with physical units can be obtained;

[0016] (7) The oxidation or reduction peak current of the electrode to be tested obtained by the electrochemical workstation is divided by the oxidation or reduction peak current density in physical units obtained by the optical sensor to obtain the active area of ​​the electrode to be tested.

[0017] The present invention also provides a detection device for the active area of ​​a flow battery electrode, comprising an electrode to be tested and a container, wherein an electrolyte is contained in the container, the electrolyte permeates the electrode to be tested, and a potential scanning system and an optical sensing system are used to simultaneously perform in-situ detection on the electrochemical reaction of the electrode to be tested. The potential scanning system comprises a three-electrode system module, and the optical sensing system comprises an incident light module, an optical sensing module, and a phase modulation module; the incident light module is used to provide 45° linearly polarized light, the optical sensing module is a prism, and the phase demodulation module is used to simultaneously obtain the reflected light phase change information of the sensing interface, and one interface of the prism is in contact with the electrode to be tested.

[0018] Furthermore, it also includes an electrochemical workstation, which is used to drive the three-electrode system module to perform an electrochemical reaction. It also includes a computer for receiving voltammetric curves, which displays the cyclic voltammetric curves obtained by the electrochemical workstation. It also includes a computer for receiving spectral images, which is used to receive spectral images formed by the phase modulation module.

[0019] Furthermore, the three-electrode system module includes a working electrode, a counter electrode and a reference electrode. The working electrode is a platinum wire inserted into the electrode to be tested, the counter electrode is a graphite rod, and the reference electrode is a saturated calomel electrode.

[0020] Furthermore, the incident light module is 45° linearly polarized light with a wavelength range of 800nm ​​to 890nm, and its components are horizontally polarized light and vertically polarized light of equal value.

[0021] Furthermore, the liquid flow battery to be tested is an all-vanadium liquid flow battery, and the electrode material of the electrode to be tested is graphite felt.

[0022] The beneficial effects of the present invention are as follows: the present invention is easy to operate, and uses a more sensitive phase-type optical sensor combined with an electrochemical workstation to perform in-situ detection of the active area of ​​an electrode, thereby providing the active area actually participating in the electrochemical reaction, and providing a technical tool for characterizing the active area of ​​an electrode participating in an electrochemical reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a specific flow chart of the in-situ detection method of the active area of ​​the electrode material participating in the electrochemical reaction;

[0024] Figure 2 This is a schematic diagram of a phase-type optical sensor and a three-electrode system module for in-situ detection of electrode active area, wherein 1, incident light module, 2, optical sensing module, 3, phase adjustment module, 4, three-electrode system module;

[0025] Figure 3 It is a schematic diagram of an in-situ detection system of the active area of ​​a liquid flow battery electrode by a phase-type optical sensor during a cyclic voltammetry process or a linear scanning voltammetry process; wherein 11, a superluminescent diode SLD, 12, a collimating lens, 13, a bandpass filter, 14, a first polarizer, 15, a prism, 16, a phase retarder, 17, a second polarizer, 18, a converging lens, 19, a spectrometer, 21, an electrode to be tested, 22, a platinum wire, 23, a graphite rod, 24, a saturated calomel electrode, 25, a container, 26, an electrochemical workstation, 31, a computer for receiving a spectral image, and 32, a computer for receiving a voltammetric curve;

[0026] Figure 4 The results of the uniform adjustable electrode calibration experiment are shown in Figure (a), where Figure (b) is a diagram of the only reaction interface of the uniform electrode, Figure (c) is a diagram of the current density obtained by the electrochemical workstation at different potential scan rates, Figure (d) is a diagram of the linear relationship between the current density obtained by the electrochemical workstation and the relative current density obtained by the optical sensor given by linear fitting;

[0027] Figure 5It is a schematic diagram of the process of optical sensor detecting the active area of ​​electrode material participating in electrochemical reaction during cyclic voltammetry, wherein (a) is the electrode cyclic voltammetry curve obtained by the electrochemical workstation, (b) is the detection signal spectrum obtained by the phase-type optical sensor; (c) is the center wavelength-time series change diagram; (d) is the cyclic voltammetry curve of the optical sensor obtained by deconvolution calculation with the help of the linear relationship of the calibration experiment. DETAILED DESCRIPTION

[0028] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation modes.

[0029] It should be noted that, in the process of driving the electrode to perform cyclic voltammetry test by the electrochemical workstation, an optical sensor is used to detect in real time the changes in the electrolyte on the electrode participating in the redox reaction process. This process calculates the current density of the electrode by collecting the optical signal changes caused by the change in the refractive index of the electrolyte. The electrochemical workstation can obtain its current, so the electrode active area can be obtained by dividing the two. Specifically, taking a prism-coupled reflective phase-type optical sensor as an example, when linearly polarized light is incident on the sensing interface where the prism contacts the electrode at an angle greater than the total reflection angle, there is a difference in the phase change of the p-polarized light and the s-polarized light at the interface. At the same time, since the refractive index of the prism is fixed, the phase change of the p-polarized light and the s-polarized light has a quantitative relationship with the refractive index of the electrolyte near the electrode to be tested, and there is a high-sensitivity dynamic range within a certain refractive index range. The present invention uses the optical sensor to adjust to this dynamic range to detect the electrochemical reaction of the electrode.

[0030] The present invention uses the redox reaction of the electrode to be tested in the cyclic voltammetry process in a three-electrode system as an example to obtain the electrode active area. Among them, the electrochemical reaction of the electrode will cause the concentration of active ions of different valence states in the electrolyte to change, thereby causing the refractive index at the interface to change, and finally reflected in the phase change of the reflected light. Considering that the incident light is linearly polarized light with a certain wavelength range, a phase difference is generated at the sensing interface, and the reflective spectrum is a double-peak shape when the high-sensitivity dynamic range condition is met. In this way, the phase change can be measured by the change in the central wavelength of the double peak of the spectrum. At this point, the relationship between the change in the interface refractive index and the change in the central wavelength is constructed, which can reflect the sensitivity of the system. Next, similar to the literature (Science 327, 1363 (2010)), it can be obtained that the central wavelength of the spectrum of the phase-type optical sensor and the current density satisfy the following relationship:

[0031] Where i(t) is the current density, deconvolution is the deconvolution calculation, n is the number of electrons in the redox reaction, F is the Faraday constant, b is a physical quantity related to the diffusion coefficient of the reduced and oxidized substances and the sensitivity of the optical sensing system, Δλ(t) is the change in the central wavelength signal, π is the circumference, and t is time. In this way, a theoretical method for optical sensors to measure the current density of electrode electrochemical reactions was constructed.

[0032] The present invention adopts a prism-coupled total reflection optical path system, and directly couples the prism in the system with the electrode to be tested to realize in-situ detection of the active area of ​​the electrode. Cyclic voltammetry test is performed on the electrode with the help of an electrochemical workstation to obtain a cyclic voltammetry curve, whose ordinate represents the current of the entire electrode. At the same time, the change in the valence state of the active substance in the electrolyte on the electrode causes a change in the refractive index, which is reflected in the change in the central wavelength of the optical sensor detection signal. The current density can be obtained through the relationship between the change in the central wavelength signal obtained above and the current density. In this way, the active area of ​​the electrode can be obtained by dividing the overall current obtained by the electrochemical workstation by the current density obtained by the optical sensor, which provides a new method for in-situ detection of the active area of ​​the electrode.

[0033] The present invention is an in-situ detection method for the active area of ​​a flow battery electrode participating in an electrochemical reaction, and the steps are as follows:

[0034] In the first step, the electrode to be tested is transferred as a working electrode into the three-electrode system module and immersed in the electrolyte so that it is in close contact with the prism, and then the module is assembled into the sensor optical path;

[0035] The second step is to adjust the reflective phase optical sensor to the full reflection state and make the optical system state within the dynamic range with the highest sensitivity, while recording the initial optical signal of the sensor;

[0036] The third step is to perform cyclic voltammetry test on the electrode immersed in the electrolyte with the help of an electrochemical workstation to obtain a cyclic voltammetry curve and extract the oxidation or reduction peak current. At the same time, the phase-type optical sensor collects the reflected light signal that changes with time. The curve of the change of the central wavelength with time is calculated from the reflected light signal;

[0037] The fourth step is to use the relationship between the central wavelength and the current density to convert the obtained central wavelength change curve with time into a relative current density change curve, and extract the relative value of the oxidation or reduction peak current density;

[0038] The fifth step is to determine the relationship between the current density obtained by the electrochemical workstation and the relative current density obtained by the optical sensor by performing cyclic voltammetry tests on a uniformly adjustable electrode with known area at different potential scan rates.

[0039] The sixth step is to obtain the absolute value of the current density collected by the optical sensor at the electrode to be tested during the cyclic voltammetry process based on the above relationship, so that the oxidation or reduction peak current density with physical units can be obtained.

[0040] The seventh step is to divide the oxidation or reduction peak current of the electrode to be tested obtained by the electrochemical workstation by the optical sensor to obtain the corresponding oxidation or reduction peak current density with physical units, so as to obtain the active area of ​​the electrode to be tested.

[0041] Specifically, the present invention uses graphite felt, an electrode material of a flow battery, as an example to study the in-situ detection process of the active area of ​​the electrode material. A reflective phase optical sensor is selected to detect the refractive index of the electrolyte during the electrode cyclic voltammetry process, and then the electrode current density is obtained. Combined with the current obtained by the electrochemical workstation, the active area of ​​the electrode is finally obtained, providing a technical tool for characterizing the active area of ​​the electrode participating in the electrochemical reaction.

[0042] The present invention is further described below in conjunction with the accompanying drawings and a preferred specific implementation manner.

[0043] Figure 1 The main implementation flow chart of the present invention is shown in FIG. 1 . The electrode to be tested is used as the working electrode in the three-electrode system, while the counter electrode is a graphite rod and the reference electrode is a saturated calomel electrode. Based on the three-electrode system, an electrochemical workstation is used to perform the electrochemical test on the electrolyte (0.1 M VO 2+ The working electrode of 2M H2SO4 was scanned at a voltage window of 0.5 V to 1.2 V at a scan rate of 1 mV s -1 Cyclic voltammetry is performed to obtain a cyclic voltammetry curve, and then the oxidation or reduction peak current is obtained. During the cyclic voltammetry process, a reflective optical sensor is used to collect optical response signals, thereby obtaining the real-time refractive index change of the electrolyte, and the corresponding cyclic voltammetry curve is obtained by using the quantitative relationship between the refractive index and the current density. At this time, the relative current density is obtained.

[0044] By performing linear sweep voltammetry tests on uniformly adjustable electrodes at different potential scan rates, the obtained current is divided by the reaction area to obtain the electrochemical current density. At the same time, the optical sensor can also obtain a linear sweep voltammetry curve, which can obtain the relative current density at different potential scan rates. In this way, the current density obtained by the electrochemical workstation and the relative current density obtained by the optical sensor can be combined to obtain the relationship between the two. Therefore, this calibration experiment enables the optical sensor to obtain a current density with physical units.

[0045] For the electrode to be tested, the relationship obtained from the above calibration experiment is used to obtain the current density with physical units, and then the oxidation or reduction peak current density is determined. Finally, the peak current obtained by the electrochemical workstation is divided by the peak current density obtained by the optical sensor to obtain the active area of ​​the electrode material to be tested that participates in the electrochemical reaction, thereby achieving the purpose of providing in-situ characterization of the active area for electrode modification.

[0046] Figure 2 is an example of a module diagram for characterizing the active area of ​​an optical sensor and a three-electrode system. Figure 2 As shown, the characterization system is composed of four modules. The incident light module 1 is a 45° linear polarized light with a wavelength range of 800nm ​​to 890nm, and its components are equal horizontal polarized light and vertical polarized light. The optical sensing module 2 is a high refractive index equilateral prism, one of the interfaces of which is in contact with the electrode to be tested. The refractive index change of the electrolyte at the sensing interface in contact with the electrode to be tested (such as graphite felt, etc.) is measured by obtaining the phase change of the reflected light after the high refractive index prism. The phase demodulation module 3 simultaneously obtains the phase change information of the reflected light at the sensing interface, such as the change in the central wavelength of the spectrum curve collected by the spectrometer to reflect the phase change. The refractive index change of the electrolyte at the sensing interface is obtained from the quantitative relationship between the phase change and the refractive index, and then the current density is obtained by deconvolution calculation. The three-electrode system module 4 mainly performs cyclic voltammetry test on the electrode to be tested immersed in the electrolyte through the electrochemical workstation, and studies the oxidation-reduction reaction of the electrolyte at the electrode during the cyclic voltammetry process to change the refractive index, and the current density of the electrode at that location can be obtained by calculation.

[0047] Figure 3 This is an example of a system that uses a phase optical sensor to detect in situ the active area of ​​an electrode involved in an electrochemical reaction during cyclic voltammetry. Figure 3As shown, the incident light module 1 includes a superluminescent diode SLD 11, a collimating lens 12, a bandpass filter 13 and a first polarizer 14. In the incident light module 1, the light emitted by the superluminescent diode SLD 11 is guided out by the optical fiber and passes through the collimating lens 12, the bandpass filter 13 and the first polarizer 14 to form a 45° linear polarized light, which is incident on the optical sensor module at a greater than total reflection angle. In this embodiment, the optical sensor module 2 is a prism 15 with a refractive index of 1.75. After total reflection occurs at the contact interface between the prism 15 and the electrode to be measured 21, the phase demodulation module 3 obtains the phase difference change of the horizontal and vertical polarized light. The phase demodulation module 3 includes a phase retarder 16, a second polarizer 17, a converging lens 18 and a spectrometer 19. Among them, the phase retarder 16 is adjusted so that the system is in the most sensitive dynamic range. The second polarizer 17 is in an almost orthogonal state with the first polarizer 14, so that the detection signal of the spectrometer 19 appears on the computer 31 receiving the spectrum image, showing a double peak situation. The three-electrode system module 4 includes a working electrode, a counter electrode and a reference electrode. The platinum wire 22 is inserted into the electrode to be tested 21 as the working electrode, the graphite rod 23 is used as the counter electrode, and the saturated calomel electrode 24 is used as the reference electrode. The container 25 contains an electrolyte (0.1M VO 2+ and 2M H2SO4) to penetrate the electrode to be tested 21. The electrochemical workstation 26 drives the three-electrode system to perform an electrochemical reaction, and the change in the valence state of the electrolyte causes its refractive index to change, thereby affecting the phase change of the polarized light. The computer 32 receiving the voltammetric curve displays the cyclic voltammetric curve obtained by the electrochemical workstation. At this time, the response signal of the optical sensor is a double peak with one rise and one fall. The refractive index change of the interface is obtained by calculating the change in its central wavelength. Assuming nF / b=1, the relative current density can be obtained by deconvolution calculation. In order to obtain the absolute value of the current density with physical quantity, a calibration experiment is required.

[0048] Figure 4 The result of the calibration experiment is shown in Figure 2. -1 , 4mV s -1 , 6mV s -1 , 8mV s -1 and 10mV s -1 ) to perform linear sweep voltammetry test. Figure 4 As shown in (a), the side of the uniformly adjustable electrode that contacts the prism is not sticky with tape, which serves as the only reaction interface with a known area. The other sides are all stuck with tape and cannot participate in the electrochemical reaction. In this way, the current obtained by the electrochemical workstation is divided by the known area to obtain the current density at different potential scan rates, such as Figure 4 (b). At the same time, Figure 4(c) The corresponding relative current density obtained by the optical sensor is given. The oxidation peak currents of the two systems at different potential scan rates are obtained, i.e. pa(EW) and i pa(OS) , and painted on Figure 4 (d). The linear relationship between the current density obtained by the electrochemical workstation and the relative current density obtained by the optical sensor is given by linear fitting, so that the calibration experiment enables the optical sensor to obtain a current density with physical units.

[0049] Figure 5 This is a schematic diagram of the process by which an optical sensor detects the active area of ​​an electrode material participating in an electrochemical reaction during cyclic voltammetry. Figure 5 (a) shows the electrode cyclic voltammetry curve obtained by the electrochemical workstation. Taking the fiber-woven graphite felt as an electrode, the active area of ​​the electrode is unknown. The electrochemical workstation obtains the current value, and its oxidation peak current is taken as I pa At the same time, the detection signal obtained by the phase optical sensor is as follows Figure 5 (b) The double peak spectrum is shown by the solid line. During the cyclic voltammetry process, the redox reaction causes the electrolyte valence state to change, resulting in a change in the refractive index. Therefore, the double peak detection signal intensity shows an increase and decrease as shown by the dotted line. The central wavelength of the double peak spectrum is calculated as the detection index. Figure 5 (c) is the central wavelength-time series change diagram. During the entire cyclic voltammetry process, when the potential reaches the oxidation potential, the oxidation process causes the central wavelength to drop sharply, and when the potential reaches the reduction potential, the reduction process causes the central wavelength to rise sharply to the initial state. Figure 5 As shown in (d), the cyclic voltammetry curve of the optical sensor is obtained by deconvolution calculation and with the help of the linear relationship of the calibration experiment. The sensor is a reflective optical sensing structure (the penetration depth of the evanescent wave is several hundred nanometers), and the current density obtained is in physical units, and its oxidation peak current density is taken as i pa The active area participating in the electrochemical reaction is I pa / i pa This provides a method to characterize the active area of ​​the electrode material.

[0050] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for detecting the active area of ​​a flow battery electrode, characterized in that: The potential scanning system and the optical sensing system are used to simultaneously detect the electrochemical reaction of the electrode in situ. The optical sensing system calculates the current density of the electrode by collecting the optical signal changes caused by the refractive index changes of the electrolyte. The potential scanning system obtains the electrode current. The electrode current divided by the current density is the electrode active area. The optical sensing system is a prism-coupled total reflection optical path system, and the prism-coupled total reflection optical path system includes a prism-coupled reflective phase-type optical sensor; The change in the valence state of the active substance in the electrolyte on the electrode causes a change in the refractive index, which is reflected in the change in the central wavelength of the optical sensor detection signal. The current density is obtained according to the relationship between the change in the central wavelength signal and the current density. The detection method includes the following steps: (1) The electrode to be tested is installed as a working electrode into a three-electrode system module and immersed in an electrolyte so that it is in close contact with the prism of the optical sensing system, and then the module is assembled into the optical path of the sensor; (2) adjusting the reflective phase optical sensor to a total reflection state and making the optical system state within a dynamic range with the highest sensitivity, while recording the initial optical signal of the sensor; (3) performing a cyclic voltammetry test on the electrode immersed in the electrolyte with the aid of an electrochemical workstation to obtain a cyclic voltammetry curve, extracting the oxidation or reduction peak current, and simultaneously collecting a reflected light signal that changes with time with a phase-type optical sensor, and calculating a curve of the change of the central wavelength with time from the reflected light signal; (4) using the relationship between the central wavelength and the current density, converting the obtained central wavelength variation curve over time into a relative current density variation curve, and extracting the relative value of the oxidation or reduction peak current density; (5) determining the relationship between the current density obtained by the electrochemical workstation and the relative current density obtained by the optical sensor by performing cyclic voltammetry tests at different potential scan rates on a uniformly tunable electrode with known area; (6) According to the above relationship, the absolute value of the current density collected by the optical sensor during the cyclic voltammetry of the electrode to be tested can be obtained, and the oxidation or reduction peak current density with physical units can be obtained; (7) The oxidation or reduction peak current of the electrode to be tested obtained by the electrochemical workstation is divided by the oxidation or reduction peak current density in physical units obtained by the optical sensor to obtain the active area of ​​the electrode to be tested.

2. The detection method according to claim 1, characterized in that: The potential scanning system performs in-situ detection of the electrochemical reaction of the electrode to drive the electrode to perform a cyclic voltammetry test for the electrochemical workstation. The system of the cyclic voltammetry test is a three-electrode system.

3. A device for detecting the active area of ​​a flow battery electrode, which uses the method for detecting the active area of ​​a flow battery electrode as claimed in any one of claims 1 to 2, characterized in that: The invention comprises an electrode to be measured (21), a potential scanning system and an optical sensing system. The potential scanning system comprises a three-electrode system module (4). The optical sensing system comprises an incident light module (1), an optical sensing module (2) and a phase demodulation module (3). The incident light module (1) comprises a superluminescent diode (SLD) (11), a collimating lens (12), a bandpass filter (13) and a first polarizer (14). The incident light module (1) is used to provide 45° linear polarized light. The optical sensing module (2) is used to measure the refractive index change of the electrolyte at the sensing interface in contact with the electrode to be measured (21). The phase demodulation module (3) is used to simultaneously obtain the reflected light phase change information of the sensing interface. The optical sensing module (2) is a prism (15). One interface of the prism (15) is in contact with the electrode to be measured (21).

4. The detection device according to claim 3, characterized in that: It also includes an electrochemical workstation (26), which is used to drive the three-electrode system module (4) to perform an electrochemical reaction, and also includes a computer (32) for receiving a voltammetric curve, and the computer (32) for receiving a voltammetric curve displays the cyclic voltammetric curve obtained by the electrochemical workstation (26). It also includes a computer (31) for receiving a spectral image, and the computer (31) for receiving a spectral image is used to receive the spectral image formed by the phase demodulation module (3).

5. The detection device according to claim 4, characterized in that: The three-electrode system module (4) comprises a working electrode, a counter electrode and a reference electrode. The working electrode is a platinum wire (22) inserted into the electrode to be tested (21), the counter electrode is a graphite rod (23), and the reference electrode is a saturated calomel electrode (24).

6. The detection device according to claim 5, characterized in that: The incident light module (1) is 45° linearly polarized light with a wavelength range of 800nm ​​to 890nm, and its components are horizontally polarized light and vertically polarized light of equal value.

7. The detection device according to claim 6, characterized in that: The liquid flow battery to be tested is an all-vanadium liquid flow battery, and the electrode material of the electrode (21) to be tested is graphite felt.

Images