Electrode, system and method for in-situ monitoring based on spectrometry

Abstract

The invention relates to the technical field of chemical molecule concentration detection, in particular to an electrode, system and method for in-situ monitoring based on spectrometry, comprising a gas diffusion layer which is provided with a plurality of pores for gas and light to pass through; the fluorescent probe layer is arranged on the upper end face of the gas diffusion layer, and the projection area of the fluorescent probe layer in the end face direction is D1; the catalyst layer is arranged on the upper end face of the fluorescent probe layer, the projection area of the catalyst layer in the end face direction is D2, and D2 covers D1; wherein the fluorescent probe layer comprises a fluorescent molecular probe which has specific recognition and reversible response to CO2. Compared with a microenvironment monitoring technology for measuring local pH only by using an in-situ Raman spectrum, the method disclosed by the invention has the advantages that the fluorescence probe is added between the catalyst layer and the gas diffusion layer, a fluorescence spectrum signal related to the CO2 concentration is additionally obtained, and in-situ measurement of the local pH and the local CO2 concentration is realized.

Description

Technical Field

[0001] This invention relates to the field of chemical molecule concentration detection technology, and in particular to an electrode, system, and method for in-situ monitoring based on spectrometry. Background Technology

[0002] The microenvironment of chemical reactions has a significant impact on their occurrence; however, the development of in-situ monitoring methods for this microenvironment has been relatively slow. Electrochemical CO2 reduction for fuel production is considered a promising pathway to achieving the "dual carbon" goal. Numerous scientific studies have shown that the local pH and local CO2 concentration near the electrode are key microenvironmental factors influencing the activity and selectivity of the electrochemical CO2 reduction reaction. By accurately measuring the local CO2 concentration and local pH near the electrode during the reaction process, a deeper understanding of the fundamental mechanism of the electrochemical CO2 reduction reaction can be achieved, providing data references for improving reaction activity, optimizing CO2 utilization, and enhancing energy efficiency.

[0003] Quantitative measurement techniques for chemical molecule concentrations can be mainly divided into spectroscopic and non-spectral methods based on their measurement principles. Non-spectral methods primarily include gas chromatography, chemical analysis, and nuclear magnetic resonance spectroscopy. However, these methods, due to their point-by-point sampling and long processing times, cannot meet the needs for rapid online monitoring of the microenvironment of chemical reactions. Spectroscopic methods include fluorescence spectroscopy, colorimetry, infrared absorption spectroscopy, and Raman spectroscopy.

[0004] For example, Chinese utility model patent CN223107624 discloses "an in-situ online measurement device for CO2 concentration in flue gas based on infrared absorption spectroscopy," which achieves in-situ measurement of CO2 concentration in flue gas through a light source reflection module. However, this method suffers from the problem of being greatly affected by the local environment and having a weak received signal strength due to the complex local environment of the chemical reaction and the weak absorption of infrared spectra by CO2.

[0005] Fluorescence spectroscopy, with its high sensitivity, fast response, and strong emission signal, enables selective measurement of CO2 concentration. Raman spectroscopy, due to its wide measurement range, high sensitivity, and non-invasive nature, is increasingly being used for in-situ monitoring of local pH during chemical reactions.

[0006] Current research on the microenvironment of electrochemical CO2 reduction reactions mainly focuses on monitoring and controlling single variables, namely local CO2 concentration or local pH. However, in actual reactions, changes in another influencing factor are unavoidable. Therefore, in-situ monitoring of these two main microenvironmental factors—local CO2 concentration and local pH—is of great significance for the further development of electrochemical CO2 reduction technology. Summary of the Invention

[0007] In this section, as well as in the abstract and title of this application, some simplifications or omissions may be made to avoid obscuring the purpose of this section, the abstract, and the title of this application, and such simplifications or omissions shall not be used to limit the scope of the invention.

[0008] To address the shortcomings of existing technologies, one objective of this invention is to provide an electrode for in-situ monitoring based on spectroscopy.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: an electrode for in-situ monitoring based on spectroscopy, comprising a gas diffusion layer having a plurality of pores along the Z direction for gas and light to pass through; a fluorescent probe layer disposed on the upper end face of the gas diffusion layer, with a projection area D1 along the Z direction on the end face; and a catalyst layer disposed on the upper end face of the fluorescent probe layer, with a projection area D2 along the Z direction on the end face, and D2 covering D1.

[0010] The fluorescent probe layer contains fluorescent molecular probes that have specific recognition and reversible response to the gas to be tested.

[0011] As a preferred embodiment of the electrode for in-situ monitoring based on spectrometry according to the present invention, wherein: the fluorescent probe layer is made of 8-hydroxypyrene-1,3,6-trisulfonic acid molecules with fluorescent properties and 4,4'-diphenylbipyridine ligand Ru(dph-bpy)3. 2+ At least one of its derivatives.

[0012] As a preferred embodiment of the electrode for in-situ monitoring based on spectroscopy according to the present invention, the gas diffusion layer is carbon paper, carbon cloth, or a metal substrate with a porous structure.

[0013] As a preferred embodiment of the electrode for in-situ monitoring based on spectroscopy according to the present invention, the catalyst layer is made of at least one of the following: elemental, alloy, oxide or single-atom form of copper, gold, silver, tin, bismuth, zinc, iron, cobalt or nickel.

[0014] As a preferred embodiment of the electrode for in-situ monitoring based on spectroscopy according to the present invention, the catalyst layer is made of copper or silver.

[0015] To address the shortcomings of existing technologies, another objective of this invention is to provide a system for in-situ monitoring of CO2 concentration and pH based on spectroscopic methods.

[0016] To achieve the above objectives, the present invention adopts the following technical solution: a system for in-situ monitoring of CO2 concentration and pH based on spectrometry, comprising the aforementioned electrode for in-situ monitoring based on spectrometry, and further comprising a Raman spectroscopy module, which includes a first laser source, wherein the Raman light signal emitted by the first laser source is configured to face the end face of the electrode where the catalyst layer is located; and a fluorescence spectroscopy module, which includes a second laser source, wherein the fluorescence light signal emitted by the second laser source is configured to face the end face of the electrode opposite to the end face where the catalyst layer is located.

[0017] As a preferred embodiment of the system for in-situ monitoring of CO2 concentration and pH based on spectroscopy according to the present invention, the Raman spectroscopy module further includes a confocal microscope, which includes an incident end for receiving incident light emitted from a first laser source, a focusing end for focusing light toward the surface of the catalyst layer, and a reflecting end for transmitting reflected light; and a Raman signal receiving system configured to receive and analyze the reflected light signal transmitted by the reflecting end of the confocal microscope.

[0018] As a preferred embodiment of the system for in-situ monitoring of CO2 concentration and pH based on spectroscopy according to the present invention, the fluorescence spectroscopy module further includes a Y-shaped optical fiber, which includes a common end connected to the end face of the electrode opposite to the catalyst layer, and two branch ends communicatively connected to the common end.

[0019] The two branches are respectively connected to the second laser source and the fluorescence spectrometer.

[0020] As a preferred embodiment of the system for in-situ monitoring of CO2 concentration and pH based on spectroscopy according to the present invention, the fluorescence spectroscopy module further includes an optical fiber microneedle, the end of which is aligned with the common end of the Y-shaped optical fiber, and the distance between the end of the optical fiber microneedle and the electrode surface is adjustable, with an adjustment range of 0.01 mm to 10 mm.

[0021] As a preferred embodiment of the system for in-situ monitoring of CO2 concentration and pH based on spectroscopy according to the present invention, wherein: the common end of the Y-shaped optical fiber is perpendicular to the electrode surface through the optical fiber microneedle.

[0022] To address the shortcomings of existing technologies, another objective of this invention is to provide a method for in-situ monitoring of CO2 concentration and pH based on spectroscopic methods.

[0023] To achieve the above objectives, the present invention adopts the following technical solution: a method for in-situ monitoring of CO2 concentration and pH based on spectroscopic methods, comprising the following steps: providing the above-mentioned electrode for in-situ monitoring based on spectroscopic methods, and placing it as the working electrode in the reaction environment; acquiring Raman scattering spectra from one side of the catalyst layer of the electrode, and analyzing the HCO3 in the obtained Raman spectra.- With CO3 2- The characteristic peak information is used to calculate the local pH value near the electrode; simultaneously, fluorescence emission spectra are collected from the gas diffusion layer side of the electrode, and the local CO2 concentration near the electrode is calculated by analyzing the obtained fluorescence spectral signals.

[0024] As a preferred embodiment of the method for in-situ monitoring of CO2 concentration and pH based on spectroscopic methods according to the present invention, wherein: the calculation of the local pH value near the electrode includes: The formula for calculating the local pH value is: ; Where Ka is HCO3 - The dissociation constant, [CO3] 2- ] / [HCO3 - [CO3] 2- Ions and HCO3 - The concentration ratio of ions.

[0025] As a preferred embodiment of the method for in-situ monitoring of CO2 concentration and pH based on spectroscopic methods described in this invention, it further includes a calibration step prior to the operation steps: establishing a calibration step using several sets of KHCO3 and K2CO3 mixed solutions with known pH values ​​for HCO3. - With CO3 2- A calibration curve was established between the Raman characteristic peak area ratio and pH value; a calibration curve between the fluorescence spectral characteristic signal intensity and CO2 concentration was established using several sets of calibration samples coated with the same fluorescent probe layer under known CO2 concentration atmospheres.

[0026] The beneficial effects of this invention are as follows: This invention enables rapid and accurate online monitoring of changes in local CO2 concentration and local pH during chemical reactions. Compared to microenvironment monitoring techniques that only use in-situ Raman spectroscopy to measure local pH, by adding a fluorescent probe between the catalyst layer and the gas diffusion layer, an additional fluorescence spectral signal related to CO2 concentration is obtained, achieving in-situ measurement of local pH and local CO2 concentration. Compared to directly using infrared absorption spectroscopy to measure CO2 concentration, the fluorescence signal emitted by the fluorescent probe has better anti-interference ability, resulting in a more accurate local CO2 concentration. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1This is a schematic cross-sectional view of the electrode structure used for in-situ monitoring based on spectroscopy in this invention.

[0029] Figure 2 This is a locally enlarged structural diagram of the electrode gas diffusion layer used for in-situ monitoring based on spectroscopy in this invention;

[0030] Figure 3 This is a schematic diagram of the system composition for in-situ monitoring of CO2 concentration and pH based on spectroscopic methods according to the present invention;

[0031] Figure 4 This is a schematic diagram of the Raman spectroscopy module of the system for in-situ monitoring of CO2 concentration and pH based on spectroscopic methods according to the present invention.

[0032] Figure 5 HCO3 obtained in Example 6 - (1014 cm) -1 ) and CO3 2- (1065 cm) -1 Calibration curve of peak area ratio versus local pH;

[0033] Figure 6 This is the result of online monitoring of local pH changes in Example 7;

[0034] Figure 7 The spectral signals acquired in Example 8 and the fitted excitation light reflection signal and fluorescence emission spectrum are shown.

[0035] Figure 8 The calibration curve of relative fluorescence emission intensity versus CO2 concentration obtained in Example 8;

[0036] Figure 9 This is the result of online monitoring of local CO2 concentration changes in Example 9. Detailed Implementation

[0037] To make the objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0038] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0039] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0040] Example 1

[0041] Reference Figure 1 and Figure 2 This is the first embodiment of the present invention. This embodiment provides an electrode for in-situ monitoring based on spectroscopy. The electrode part is composed of a gas diffusion layer 100, a fluorescent probe layer 200 and a catalyst layer 300.

[0042] Specifically, the gas diffusion layer 100 is a gas diffusion layer substrate with good gas permeability, on which a number of pores K are distributed to allow gas and light to pass through. As the substrate of the electrode, its porous structure allows the reactive gas CO2 to diffuse efficiently and uniformly from the back to the surface of the catalyst layer 300; in addition, the light transmittance of the gas diffusion layer 100 allows laser light incident from the back of the electrode to penetrate this layer and reach the internal fluorescent probe layer 200; at the same time, the fluorescence generated inside can also penetrate this layer in the reverse direction and be collected.

[0043] The fluorescent probe layer 200 is located between the catalyst layer 300 and the gas diffusion layer 100. The fluorescent probe layer 200 is loaded with fluorescent molecules (such as HPTS) that are sensitive to CO2 concentration (typically exhibiting fluorescence quenching). When CO2 gas permeates from the gas diffusion layer 100 and dissolves in the medium of this layer, it causes a regular change in the luminescence characteristics of the fluorescent molecules (such as a decrease in intensity). This layer is crucial for achieving in-situ sensing of CO2 concentration within the electrode.

[0044] Furthermore, catalyst layer 300 is the active site for the electrochemical reduction of CO2 (CO2RR). The catalyst (such as Cu) converts CO2 into the target product (such as ethylene, ethanol, etc.). The reaction consumes CO2 and produces OH-. - This directly alters the local microenvironment at the electrode / electrolyte interface (i.e., the object to be monitored in this invention).

[0045] In this embodiment, the fluorescent probe layer 200 is disposed on the upper end face of the gas diffusion layer 100, and its projected area in the end face direction is D1. The catalyst layer 300 is disposed on the upper end face of the fluorescent probe layer 200, and its projected area in the end face direction is D2, forming a structure of sequential longitudinal stacking. Since D2 covers D1, the advantage of this arrangement is that the catalyst layer 300 can completely cover the fluorescent probe layer 200, thus sealing the fluorescent probe inside the electrode and realizing true in-situ interface sensing.

[0046] Firstly, the catalyst layer 300 is typically a dense thin film formed by catalyst particles (such as Cu nanoparticles) and a polymer binder (such as Nafion). When it completely covers the underlying fluorescent probe layer 200, it forms a liquid-impermeable physical barrier. This physical barrier achieves the following: a. Prevents probe leaching / loss, ensuring that fluorescent molecules are firmly confined within the electrode and will not dissolve or detach under long-term electrolyte immersion and fluid scouring; b. Defines a unique reactant transport path, forcing CO2 molecules diffused from the outside to reach the reaction site only through the gas diffusion layer 100, fluorescent probe layer 200, and catalyst layer 300. In this way, the CO2 concentration sensed by the fluorescent probe layer 200 strictly represents the concentration before reaching the reaction interface, and the measurement location is unique and deterministic; c. Isolates electrolyte chemical interference, preventing a large number of water molecules, other ions (such as K⁺, Cl⁻), or reaction intermediates in the electrolyte from directly contacting the fluorescent probe, avoiding problems such as fluorescence quenching and pH sensitivity interference that these substances may cause, and ensuring the specificity of the fluorescence signal response.

[0047] On the other hand, the dense and opaque catalyst layer 300 (especially the metal catalyst) serves as an effective optical isolation layer. This allows for: a) blocking stray light from the front: excitation lasers incident from the back of the electrode, after exciting the fluorescent probe, will not interfere with the reflected light or the fluorescence emitted by the probe by the laser from the front used for Raman measurements, and vice versa, thus avoiding crosstalk between the two spectral signals; b) eliminating background interference from the front: the intense electrochemical reactions of the catalyst layer 300 itself and its surface (which may produce bubbles and precipitates) can lead to complex light scattering and background fluorescence. The completely covered catalyst layer 300 shields these strong optical noises from the front, making the fluorescence signal detected from the back purer and significantly improving the signal-to-noise ratio; c) enabling simultaneous dual-path optical monitoring: it is precisely because of this layer that a simultaneous, in-situ, and non-interfering monitoring scheme for Raman spectroscopy from the front and fluorescence measurement from the back becomes possible. This is the physical basis for achieving simultaneous measurement of two parameters.

[0048] It is worth noting that the completely covered fluorescent probe layer 200 is located within a sealed interlayer consisting of a gas diffusion layer 100 and a catalyst layer 300. This results in: a) stable humidity and medium: the environment within this interlayer is relatively stable and not directly affected by electrolyte flow or convection. The properties of the medium in which the probe molecules are located (e.g., a thin film mixed with ionomers) do not change drastically, ensuring the reproducibility of its fluorescence properties (such as quantum yield and response curve); b) guaranteed calibration effectiveness: the calibration of the fluorescence intensity-CO2 concentration relationship before the experiment is performed in a simulated stable interlayer environment. Complete coverage ensures that the environment in which the probe is located is highly consistent with that during calibration in actual measurements, thus making the calibration data reliable and the measurement results accurate.

[0049] Example 2

[0050] Reference Figure 1 and Figure 2 This is the second embodiment of the present invention. The difference between this embodiment and the previous embodiment is that the fluorescent probe layer 200 is made of 8-hydroxypyrene-1,3,6-trisulfonic acid molecules and 4,4'-diphenylbipyridine ligand Ru(dph-bpy)3, which have fluorescent properties. 2+ At least one of its derivatives.

[0051] Specifically, 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS) is a highly pH-sensitive fluorescent dye. Its protonated and deprotonated forms exhibit different excitation spectra, and by selecting a specific excitation wavelength (e.g., 454 nm), its fluorescence intensity (520 nm) changes with pH. The key point is that when it combines with a hydrophobic phase transfer agent (e.g., tetraoctylammonium hydroxide), its pH sensitivity in the aqueous phase is transformed into sensitivity to gaseous CO2. CO2 diffuses into the probe film, dissolves, and generates H2CO3, causing a slight local pH change, which in turn alters the fluorescence intensity of HPTS. This is an indirect but highly effective CO2 sensing mechanism.

[0052] Furthermore, 8-hydroxypyrene-1,3,6-trisulfonic acid is one of the most widely studied and classic CO2 fluorescent probes, with a clear response mechanism and a strong literature foundation. Pyrene dyes also have high fluorescence quantum yields, bright signals, and are easy to detect. In addition, there are many derivatives, and their hydrophobicity, response range, and sensitivity can be adjusted through chemical modification to adapt to different probe film matrices.

[0053] Preferably, the 4,4'-diphenylbipyridine ligand Ru(dph-bpy)3 can also be used. 2+ Its typical sensing mechanism is based on fluorescence quenching. O2 or certain analytes (such as CO2 in some designs) can act as electron acceptors, quenching the fluorescence of their excited state, leading to a decrease in fluorescence intensity or lifetime. Some studies utilize the direct dynamic quenching effect of CO2 molecules on certain Ru complexes; the Ru complex is used as a reference fluorophore, co-embedded with another CO2-sensitive response unit (such as a pH-sensitive dye). By measuring the intensity ratio or lifetime ratio of the two fluorophores, ratiometric sensing is achieved, which can significantly improve anti-interference capability.

[0054] Furthermore, the 4,4'-diphenylbipyridine ligand Ru(dph-bpy)3 was selected. 2+It has the following advantages: a. Long fluorescence lifetime: The microsecond-level long lifetime allows the use of time-resolved fluorescence technology, which can easily filter out autofluorescence (nanosecond level) from the background, electrodes or catalysts, greatly improving the signal-to-noise ratio, which is crucial for complex electrochemical environments; b. Excellent photostability: Compared with organic dyes, these metal complexes have extremely strong resistance to photobleaching, making them suitable for long-term, high-intensity in-situ continuous monitoring; c. Large Stokes shift: The absorption and emission peaks are far apart, which is beneficial for the separation of excitation and emission light and simplifies optical filter design.

[0055] The rest of the structure is the same as in Example 1.

[0056] In summary, 8-hydroxypyrene-1,3,6-trisulfonic acid represents a mature and highly sensitive route for indirect CO2 sensing based on pH conversion; 4,4'-diphenylbipyridine ligand Ru(dph-bpy)3 2+ This represents a route based on long-lifetime fluorescence quenching or ratio sensing, exhibiting excellent photostability and anti-interference capabilities. Derivatives based on these routes possess similar effects.

[0057] Example 3

[0058] Reference Figure 1 and Figure 2 This is the third embodiment of the present invention. The difference between this embodiment and the previous embodiment is that the gas diffusion layer 100 is carbon paper, carbon cloth, or a metal substrate with a porous structure.

[0059] Specifically, carbon paper and carbon cloth are three-dimensional porous networks composed of carbon fibers with a porosity as high as 70%-80%; while porous metal substrates (such as nickel foam and titanium felt) also have high porosity and interconnected channels. This structure provides a low-resistance diffusion path for gases, which is crucial for maintaining reactant supply at high current densities. It ensures that the reactive gas (CO2) can be rapidly and uniformly transported from the gas chamber on the back of the electrode to the catalyst reaction sites across the entire electrode plane.

[0060] Furthermore, carbon materials (carbon paper, carbon cloth) are themselves good conductors; porous metal substrates (such as nickel, titanium) are even better electronic conductors. This ensures that the electrons required for the electrochemical reaction can be transported with low loss. As the supporting framework for the electrode, it must be able to efficiently conduct current from the external circuit to the catalyst layer 300 on the surface.

[0061] Ideally, carbon materials themselves possess a certain degree of hydrophobicity and are easily impregnated with hydrophobic agents such as PTFE (polytetrafluoroethylene), thereby precisely controlling their hydrophobic properties and forming a stable gas-liquid-solid three-phase reaction zone. Metal substrates can also achieve similar functions through surface coatings. However, at the three-phase interface of the gas phase (CO2), liquid phase (electrolyte), and solid phase (catalyst), a balance needs to be struck between gas permeation and liquid flooding prevention. Excessive hydrophilicity can cause the pores to be flooded by the electrolyte, blocking gas channels.

[0062] The rest of the structure is the same as in Example 1.

[0063] Example 4

[0064] Reference Figure 1 and Figure 2 This is the fourth embodiment of the present invention. The difference between this embodiment and the previous embodiment is that the catalyst layer 300 is made of at least one of the following: elemental, alloy, oxide or single-atom form of copper, gold, silver, tin, bismuth, zinc, iron, cobalt or nickel. All of these are metal-based catalysts with CO2RR activity.

[0065] Preferably, the catalyst layer 300 is made of copper or silver.

[0066] Copper is a metal catalyst capable of efficiently converting CO2 into multi-carbon products (C2+). Its reaction mechanism is extremely complex, involving multiple steps of proton-electron transfer and C-C coupling. The reaction pathway and product selectivity on copper catalysts are strongly dependent on the local microenvironment at the electrode interface (i.e., the pH and CO2 concentration monitored in this invention). For example, an increased local pH favors C-C coupling but may promote the competitive hydrogen evolution reaction (HER); insufficient local CO2 concentration can cause the reaction to shift from CO2 reduction to HER, or cause the product to change from C2+ to C1.

[0067] Silver is one of the optimal catalysts for the industrial production of CO. CO is an important component of syngas and is used in downstream industrial processes such as Fischer-Tropsch synthesis. Silver catalysts exhibit extremely high selectivity for CO, but their activity and selectivity are also affected by the microenvironment. In particular, the conversion of CO2 to CO is extremely sensitive to the local CO2 concentration; accurately monitoring and maintaining a sufficient CO2 supply is crucial to ensuring the stable performance of silver catalysts at high current densities.

[0068] The rest of the structure is the same as in Example 1.

[0069] Example 5

[0070] Reference Figures 1-4This is the fifth embodiment of the present invention. This embodiment provides a system for in-situ monitoring of CO2 concentration and pH based on spectroscopic methods. It includes a Raman spectroscopy module 400 that collects Raman scattering signals from the front of the electrode (the side loaded with catalyst layer 300), and adopts the electrode part for in-situ monitoring based on spectroscopic methods in the previous embodiment and a fluorescence spectroscopy module 500 that collects fluorescence emission signals from the back of the electrode.

[0071] Specifically, the Raman spectroscopy module 400 mainly includes a first laser source 401 for generating Raman scattering, a confocal microscope 402, a spectroscopic system 404 including a mirror 404a and a filter 404b, and a Raman signal receiving system 403. The fluorescence spectroscopy module 500 includes a second laser source 501 as excitation light, a Y-type optical fiber 502, fiber microneedles 504, and a fluorescence spectrometer 503. The purpose of the fiber microneedles 504 is to fix the position of the Y-type optical fiber 502, allowing the Y-type optical fiber 502 to move freely in space to a distance from the electrode surface, thereby adjusting the intensity of the excitation light and the intensity of the received light.

[0072] Preferably, the end of the fiber optic microneedle 504 is aligned with the common end of the Y-type fiber optic 502, and the distance between the end of the fiber optic microneedle 504 and the electrode surface is adjustable, ranging from 0.01 mm to 10 mm. Adjusting the position of the fiber optic microneedle serves two purposes: firstly, to bring the Y-type fiber optic 502 closer to the electrode, allowing the excitation light to penetrate the relatively poorly transparent gas diffusion layer 100 electrode substrate and receive the weak fluorescence emission signal; secondly, to maintain a certain distance to prevent localized overheating damage to the electrode due to continuous laser irradiation.

[0073] Specifically, at extremely close distances (0.01-0.5 mm), when the tip of the fiber optic microneedle 504 is very close to the electrode surface, the excitation spot is small and the energy is concentrated, enabling efficient excitation of the fluorescent probe layer. Simultaneously, the fiber can collect fluorescence emitted over a larger solid angle, resulting in the strongest fluorescence signal and the highest signal-to-noise ratio. This is crucial when the probe signal is weak or when monitoring rapid, subtle changes is required. Measurements at this distance offer higher spatial resolution and more precisely represent the concentration of the "point" aligned with the fiber. At medium distances (0.5-3 mm), a balance between signal and safety is achieved, suitable for routine monitoring. Accidental physical contact due to vibration or thermal expansion is avoided, protecting the fragile electrodes (especially the gas diffusion layer 100) and the tip of the Y-shaped fiber 502. Signal attenuation remains within acceptable limits. A stable and reliable operating range is provided, suitable for most long-duration in-situ experiments. At greater distances (3-10 mm), it provides operational space and flexibility, allowing ample room for electrode installation and removal, as well as the arrangement of other components within the reaction cell (such as reference electrodes, counter electrodes, stir bar, and temperature probes). This significantly improves system compatibility and experimental design flexibility, enabling the monitoring technology to be easily integrated into various existing or custom-designed electrochemical reaction devices. This adjustable approach can adapt to different operating conditions.

[0074] Preferably, the common end of the Y-type optical fiber 502 is perpendicular to the electrode surface via an optical fiber microneedle 504. This perpendicularity to the electrode surface is to allow the excitation light to penetrate the gas diffusion layer 100 electrode substrate as much as possible and receive the weak emission signal.

[0075] Furthermore, the first laser source 401 of the Raman spectrum is focused on the surface of the catalyst layer 300 by the spectrometer 404 and the confocal microscope 402. The reflected Raman signal is processed and analyzed by the Raman signal receiving system 403 after passing through the spectrometer 404 to obtain the local pH.

[0076] Raman scattering is typically a very weak effect because of the non-resonant interaction between the excited photons and the molecules involved in the scattering process. The biggest interfering factor in Raman spectroscopy is fluorescence, which, due to its resonant interaction with the electronic sample states, can easily be six orders of magnitude more efficient than Raman interactions. Confocal microscopy (402) confines the collection of fluorescence to photons emitted from the focal plane, drastically reducing the fluorescence background signal and thus obtaining clear Raman images.

[0077] The spectral splitting system 404 is an optional feature, primarily designed to adjust the optical path and perform noise reduction on the optical signal to facilitate the reception of fluorescence signals.

[0078] In the fluorescence spectroscopy module 500, the laser emitted by the second laser source 501 is guided to the back of the electrode through the Y-type optical fiber 502. After the laser penetrates the porous gas diffusion layer 100 on the back, it excites the fluorescent molecules of the fluorescent probe layer 200 to emit light of a specific wavelength. The emitted light signal enters the fluorescence spectrometer 503 through the Y-type optical fiber 502 and is analyzed to obtain the local CO2 concentration.

[0079] The specific process of in-situ monitoring of local pH and local CO2 concentration is as follows: During the reaction, HCO3 on the surface of catalyst layer 300 was monitored in situ using confocal Raman spectroscopy. - Ions and CO3 2- The local pH value is calculated by comparing the ratio of the Raman peak areas of the two ion signals. The specific formula is: (1) In formula (1), Ka is HCO3. - The dissociation constant, [CO3] 2- ] / [HCO3 - [CO3] 2- Ions and HCO3 - The concentration ratio of ions can be calculated from the area ratio of the Raman spectrum.

[0080] During the reaction, the emission spectrum signal of the fluorescent molecules is monitored in situ using a fluorescence spectrometer 503, and the local CO2 concentration is calculated by the regular relationship between the fluorescence emission spectrum and the CO2 concentration.

[0081] The rest of the structure is the same as in Example 1.

[0082] Working principle: The excitation light of the Raman signal X1 travels sequentially through a first laser source 401 that emits Raman laser light, a beam splitting system 404 (including a reflector 404a and a filter 404b), and a confocal microscope 402, until it is focused on the surface of the catalyst layer 300 on the front of the electrode. The signal light then travels sequentially through the Raman scattered light generated on the surface of the catalyst layer 300, returns along its original path to part of the excitation light path, is separated by the beam splitting system 404, and finally enters the Raman signal receiving system 403 (i.e., the confocal Raman spectrometer). This is a reflection-type confocal micro-Raman detection. The laser is incident vertically or obliquely from the electrolyte side onto the reaction interface of the working electrode (i.e., the catalyst / electrolyte interface), and the signal scattered back from this interface is collected. The detection target area is the catalyst surface and its adjacent micron-sized thin layer of electrolyte.

[0083] The excitation light path of the fluorescence signal X2 is as follows: it sequentially passes through a second laser source 501 that emits fluorescent laser light, a branch of the Y-shaped optical fiber 502, an optical fiber microneedle 504, the surface of the gas diffusion layer 100 perpendicularly directed towards the back of the electrode, and the laser penetrates the porous gas diffusion layer 100 until it excites the fluorescent probe layer 200 within the interlayer. The signal light then sequentially passes through the specific wavelength fluorescence generated by the excitation of the fluorescent probe layer 200, penetrates the gas diffusion layer 100 in the reverse direction, is collected by the tip of the optical fiber microneedle 504, and enters the fluorescence spectrometer 503 along another branch of the Y-shaped optical fiber. This is a hybrid transmission / reflection fiber fluorescence detection. Light enters from the gas chamber side or support side of the electrode, penetrates the porous substrate, excites the embedded sensor (i.e., the fluorescent probe layer 200 in this embodiment), and then collects the fluorescence signal emitted from within. The detection target area is the fluorescent probe thin film layer tightly attached to the catalyst layer.

[0084] This reverse optical path setup, with one forward and one reverse, is designed to solve a fundamental problem in in-situ monitoring, achieving the following synergistic enhancement effects: a. The two laser beams and two signals are completely separated in space, with no intersection points, achieving true "synchronization" and "in-situ" operation without interference. The strong Raman laser on the front side will not become background noise for the back fluorescence detection; the back fluorescence signal will not be mistakenly acquired by the front Raman system. This is the physical basis for enabling the two spectral systems to operate simultaneously, independently, and stably. The Raman signal X1 is directly aimed at the surface of the catalyst layer 300 where the reaction occurs, while the fluorescence signal X2 directly monitors the fluorescent probe layer 200 of the reactants. Both are measured at the most relevant locations without interfering with the reaction process.

[0085] b. Each optical path is optimized for its target signal and avoids major noise sources, maximizing signal quality and signal-to-noise ratio. Front detection directly collects the strongest scattered signal from the reaction interface. The confocal microscope 402 setting can limit the detection volume and effectively eliminate background interference from the electrolyte body. Back detection has two major advantages: (1) The catalyst layer 300, as an optical shielding layer, completely blocks all strong scattered light and background fluorescence from the front electrolyte, bubbles, and reaction products. This is the decisive design to improve the signal-to-noise ratio. (2) The fiber microneedle 504 is aligned at close range, which improves excitation and collection efficiency.

[0086] c. Because the spatial gradients of the two parameters (pH and CO2 concentration) may differ, they can precisely correspond to different "local" spatial scales. Generally, the pH gradient exists only within the nanometer to micrometer-scale double layer / gas diffusion layer 300 on the electrode surface. The small spot size and shallow depth of field of the front confocal Raman spectroscopy perfectly match this extremely thin region, measuring the true "interfacial pH." Meanwhile, CO2 exhibits a concentration decay gradient from the gas diffusion layer 100 to the catalyst layer 300 surface. The fluorescent probe layer 200 on the back acts as a thin-layer sensor, and its signal reflects the average concentration in that plane (adjacent to the catalyst layer 300). This location is precisely the most critical monitoring point for CO2 concentration before the reaction is consumed.

[0087] d. A probe for the result of a reaction (pH change) and a probe for the cause of the reaction (CO2 supply) can construct a complete analytical capability that establishes a causal link. This setup facilitates the establishment of a complete causal chain: CO2 supply (fluorescence monitoring), reaction consumption and product formation (electrochemical current), and interfacial alkalization (Raman monitoring). For example, it is possible to observe in real time how the interfacial pH increases (Raman signal change) as an increase in current leads to faster CO2 consumption (fluorescence signal change). This serves as a powerful tool for understanding reaction mechanisms and optimizing electrodes and operating conditions.

[0088] Example 6

[0089] Reference Figure 5 This is the sixth embodiment of the present invention. Unlike the previous embodiment, in this embodiment, the method for in-situ monitoring of CO2 concentration and pH based on spectroscopic methods adds a calibration step before the operation steps: using several sets of mixed solutions of KHCO3 and K2CO3 with known pH values, a calibration step is established for HCO3... - With CO3 2- A calibration curve was established between the Raman characteristic peak area ratio and pH value; a calibration curve between the fluorescence spectral characteristic signal intensity and CO2 concentration was established using several sets of calibration samples coated with the same fluorescent probe layer 200 under known CO2 concentration atmospheres.

[0090] Specifically, the gas diffusion layer 100, fluorescent probe layer 200, and catalyst layer 300 of the electrode section can be replaced with a mixed solution of KHCO3 and K2CO3 of known concentration. Based on the pH value of the mixed solution, the HCO3 content can be calibrated. - Ions and CO3 2- The ratio between the Raman peak area of ​​ions and the local pH.

[0091] like Figure 5As shown, the horizontal axis of the Raman spectrum in the upper right corner represents the Raman shift, which represents the characteristic frequencies of molecular vibrations, and the vertical axis represents the Raman signal intensity. The curves mean: the black solid line (pH 7.80) is the Raman spectrum at pH = 7.80, 10¹⁶ cm⁻¹. -1 The peak at that location corresponds to HCO3 - The vibration peak (marked "v(HCO3)" in the figure) - 1016”, at which point HCO3 - It is the dominant species, with high peak intensity. The red dashed line (pH 9.50) is the Raman spectrum at pH 9.50, 1065 cm⁻¹. -1 The peak at that location corresponds to CO3. 2- The vibration peak (marked "v(CO3)" in the figure) 2- 1065”, at which point CO3 2- As the concentration increases, the peak intensity increases significantly.

[0092] Figure 5 The horizontal axis "pH" of the calibration curve in the main graph represents the actual pH value of the solution (measured by a pH meter, etc.), and the vertical axis "log(CO3)" represents the actual pH value of the solution. 2- / HCO3 - ")" is CO3 2- With HCO3 - The logarithm of the ratio of the Raman peak areas (peak area is positively correlated with ion concentration, therefore this ratio reflects the concentration ratio of the two ions). The red line and the formula "y=0.87x-7.99" are the fitting equation for the calibration curve (y corresponds to the ordinate, x corresponds to the abscissa), indicating that log(CO3) = 0.87x - 7.99. 2- / HCO3 - CO3 is linearly positively correlated with pH (the higher the pH, the higher the CO3 content). 2- The larger the proportion, the higher the ratio. Figure 5 Chinese R 2 =0.9955 is the coefficient of determination. A value close to 1 indicates that the linear fit is excellent and the calibration curve is highly reliable.

[0093] The remaining structure is the same as in Example 5.

[0094] In summary, by measuring the peak area ratio (reflecting the concentration ratio) of the two components using Raman spectroscopy and combining it with the calibration curve, the local pH can be directly deduced from the Raman signal. This allows for the determination of the local pH and CO2-related species (HCO3-) in chemical reactions. - / CO3 2- Online monitoring of pH was performed. This demonstrates that, in addition to in-situ testing during the reaction process, it can also be used for localized, non-in-situ pH testing.

[0095] Example 7

[0096] Reference Figure 6This is the seventh embodiment of the present invention. Unlike the previous embodiment, in this embodiment, the technology can be used to monitor the local pH changes near the electrode catalyst layer 300 after the reaction.

[0097] As shown in the figure, the horizontal axis represents the reaction time (in minutes), ranging from 0 to 25 minutes; the vertical axis "pH" represents the local pH value in the region near the electrode catalyst layer at 300°. The red curve (labeled "pH@Time") reflects the dynamic relationship between "reaction time and local pH". The "stoptest" label (arrow pointing to the initial point) can be understood as the "test start point," indicating that in-situ pH monitoring begins at 0 minutes.

[0098] from Figure 6 The trend of the curve shows that as the reaction time increases from 0 to 25 minutes, the local pH continuously decreases (from an initial level of nearly 10.5 to approximately 8.0 at 25 minutes). This pH decrease corresponds to an increase in local CO2 concentration near the catalyst layer 300 (because CO2 dissolves to form carbonic acid and HCO3-). - For acidic species, the more CO2 present, the more acidic the local environment becomes.

[0099] The rest of the structure is the same as in Example 6.

[0100] In summary, the fluorescent probe layer 200 enables real-time, in-situ monitoring of the local pH near the catalyst layer 300 during the reaction process. Combined with the previously calibrated curves, pH changes can be further converted into changes in local CO2 concentration, and the interference-resistant nature of the fluorescence signal makes the result more accurate. This embodiment also demonstrates that, in addition to in-situ testing during the reaction process, it can also be used for non-in-situ local pH testing.

[0101] Example 8

[0102] Reference Figure 7 and Figure 8 This is the eighth embodiment of the present invention. Unlike the previous embodiment, in this embodiment, the fluorescent probe layer 200 uses 8-hydroxypyrene-1,3,6-trisulfonic acid molecules (HPTS) with fluorescent properties. Under excitation light with a wavelength of 454 nm, HPTS molecules emit light with a wavelength of approximately 520 nm. When combined with a phase transfer agent—tetraoctylammonium hydroxide—it can be used for quantitative monitoring of gaseous CO2 concentration. After placing the fluorescent probe on the electrode portion, the intensity of the emitted light from HPTS changes accordingly in atmospheres with different CO2 concentrations; the higher the local CO2 concentration, the weaker the intensity of the fluorescent emission light; conversely, the lower the local CO2 concentration, the stronger the intensity of the fluorescent emission light.

[0103] Figure 7The horizontal axis represents the wavelength of light (unit: nanometers), and the vertical axis represents the relative intensity of the light signal (dimensionless). The meanings of the curves in the legend are as follows: The red "Excitation spectrum" corresponds to the spectrum of light that excites HPTS—the red curve has a strong peak near 454 nm, which is a characteristic of the light source that excites HPTS molecules. The blue "Emission spectrum" corresponds to the fluorescence spectrum emitted by HPTS after excitation—the peak of the blue curve is concentrated near 520 nm, which is a characteristic of HPTS fluorescence emission. The gray "Original signal" is the total signal directly collected in the experiment, including the reflection / scattering signal of the excitation light (near 454 nm) and the fluorescence emission signal of HPTS (near 520 nm). The red and blue curves are the pure excitation light signal and pure fluorescence emission signal separated (or fitted) from the original signal, facilitating separate analysis of fluorescence characteristics.

[0104] Figure 8 This graph includes a calibration curve showing the relationship between fluorescence intensity and CO2 concentration. It quantitatively illustrates the relationship between HPTS fluorescence intensity and CO2 concentration, with the core objective of establishing a calibration from fluorescence intensity to CO2 concentration. In the main graph, the horizontal axis "CO2 Concentration (mM)" represents the local CO2 concentration (unit: millimoles / liter); the vertical axis "Relative Intensity (au)" represents the relative fluorescence emission intensity of HPTS; the curve corresponds to the formula y = 8.08x. -0.56 This is the fitted equation for relative fluorescence intensity (y) versus CO2 concentration (x). It can be seen that this is a power function relationship, meaning that as the CO2 concentration x increases, the fluorescence intensity y decreases. Figure 8 Chinese R 2 =0.9968 indicates that the coefficient of determination is close to 1, which means that the fitting effect of this quantitative relationship is excellent, and the accuracy of inferring CO2 concentration from fluorescence intensity is very high.

[0105] Figure 8 The inset in the upper right corner shows the HPTS fluorescence emission spectra at different CO2 concentrations. For example, the peak intensity is higher for 10% CO2 (low concentration) and lower for 100% CO2 (high concentration); this intuitively demonstrates that the higher the CO2 concentration, the weaker the fluorescence emission intensity, which is also the experimental basis for the calibration curve in the main graph.

[0106] The remaining structure is the same as in Example 7.

[0107] In conclusion, Figure 7 The excitation / emission spectral characteristics of HPTS were clarified (ensuring accurate differentiation between excitation light and fluorescence in experiments). Figure 8A quantitative relationship between fluorescence intensity and CO2 concentration was established (enabling the measurement of CO2 concentration using fluorescence signals). This demonstrates that, in addition to in-situ testing during the reaction process, it can also be used for localized CO2 concentration testing in non-in-situ locations.

[0108] Example 9

[0109] Reference Figure 9 This is the ninth embodiment of the present invention. Unlike the previous embodiment, in this embodiment, the catalyst layer 300 can use a Cu catalyst, and the electrode area based on the gas diffusion layer 300 is 1×1 cm². 2 When electrochemical CO2 reduction is performed on a Cu electrode, the local CO2 concentration will drop to a new concentration plateau when the concentration of CO2 consumed by the reaction is much greater than the supply rate of CO2 diffusion.

[0110] Figure 9 The horizontal axis "Time (s)" represents the time (in seconds) of the electrocatalytic CO2 reduction reaction; the vertical axis "CO2 Concentration (mM)" represents the local CO2 concentration (in millimoles per liter) near the catalyst layer at a depth of 300 mm, obtained through in-situ monitoring using a fluorescent probe. Furthermore... Figure 9 The labels on the three curves represent different cathode current densities ("-50 / -100 / -200mA / cm"). 2 The negative sign in the figure corresponds to a reduction reaction; the larger the absolute value, the faster the reaction rate.

[0111] It can be seen that, Figure 9 The overall trend of the medium curve can be divided into a rapid decline period and a concentration plateau period, corresponding to the process where the consumption rate > diffusion rate, and then the concentration drops to a new plateau. During the rapid decline period (around time 0): in the initial stage of the reaction, the local CO2 concentration is relatively high; however, after the electrocatalytic reduction reaction starts, CO2 is rapidly consumed, and at this time, the diffusion rate of CO2 from the outside to the catalyst layer is much slower than the reaction consumption rate, so the local CO2 concentration drops rapidly; while during the concentration plateau period (after time > 50s): when the reaction consumption rate and the diffusion supply rate of CO2 reach a dynamic equilibrium, the local CO2 concentration no longer decreases and stabilizes at a concentration plateau.

[0112] from Figure 9 The effect of current density on local CO2 concentration can also be observed. The larger the absolute value of the current density (the faster the reaction rate), the lower the plateau of local CO2 concentration: the red curve (-50 mA / cm²). 2 The reaction rate is the slowest: the final plateau concentration is approximately 25 mM; gray curve (-100 mA / cm²) 2 (Medium reaction rate): Final plateau concentration approximately 20 mM; Blue curve (-200 mA / cm²) 2(Fastest reaction rate): The final plateau concentration is only about 10 mM. This is because the higher the current density, the faster the CO2 consumption rate, requiring a lower local concentration to match the diffusion supply with the reaction consumption. Therefore, the plateau concentration decreases as the absolute value of the current density increases.

[0113] This embodiment Figure 9 This demonstrates intuitively how the reaction rate (current density) regulates the local CO2 concentration in electrocatalytic CO2 reduction. It also verifies that when the CO2 concentration consumed by the reaction is much greater than the CO2 diffusion supply rate, the local CO2 concentration will decrease to a new plateau. This proves that the device can also be used solely for in-situ testing of local CO2 concentration during electrochemical CO2 reduction reactions.

[0114] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An electrode for in-situ monitoring based on spectroscopic methods, characterized in that: include, A gas diffusion layer (100) has several pores (K) along the Z direction for gas and light to pass through. A fluorescent probe layer (200) is disposed on the upper end face of the gas diffusion layer (100), and its projected area on the end face along the Z direction is D1; ​​and, A catalyst layer (300) is disposed on the upper end face of the fluorescent probe layer (200), and the projection area along the Z direction in the end face direction is D2, and D2 covers D1; The fluorescent probe layer (200) contains fluorescent molecular probes that have specific recognition and reversible response to the gas to be tested.

2. The electrode for in-situ monitoring based on spectroscopic methods as described in claim 1, characterized in that: The fluorescent probe layer (200) is made of 8-hydroxypyrene-1,3,6-trisulfonic acid molecules and 4,4'-diphenylbipyridine ligand Ru(dph-bpy)3, which have fluorescent properties. 2+ At least one of its derivatives.

3. The electrode for in-situ monitoring based on spectroscopic methods as described in claim 1, characterized in that: The gas diffusion layer (100) is carbon paper, carbon cloth, or a metal substrate with a porous structure.

4. The electrode for in-situ monitoring based on spectroscopic methods as described in any one of claims 1 to 3, characterized in that: The catalyst layer (300) is made of at least one of the following: elemental, alloy, oxide or single-atom form of copper, gold, silver, tin, bismuth, zinc, iron, cobalt or nickel.

5. The electrode for in-situ monitoring based on spectroscopic methods as described in claim 4, characterized in that: The catalyst layer (300) is made of copper or silver.

6. A system for in-situ monitoring of CO2 concentration and pH based on spectroscopic methods, comprising an electrode for in-situ monitoring based on spectroscopic methods as described in any one of claims 1 to 5, characterized in that: It also includes, A Raman spectroscopy module (400) includes a first laser source (401) whose Raman light signal (X1) is configured to face the end face of the catalyst layer (300) of the electrode; and, The fluorescence spectroscopy module (500) includes a second laser source (501), the fluorescence light signal (X2) emitted by the second laser source (501) being configured to face the end face of the electrode opposite to the catalyst layer (300).

7. The system for in-situ monitoring of CO2 concentration and pH based on spectroscopic methods as described in claim 6, characterized in that: The Raman spectroscopy module (400) also includes, A confocal microscope (402) includes an incident end for receiving incident light emitted from a first laser source (401), a focusing end for focusing light toward the surface of a catalyst layer (300), and a reflecting end for transmitting reflected light; and, A Raman signal receiving system (403) is configured to receive and analyze the reflected light signal transmitted from the reflective end of the confocal microscope (402).

8. The system for in-situ monitoring of CO2 concentration and pH based on spectroscopic methods as described in claim 6 or 7, characterized in that: The fluorescence spectroscopy module (500) also includes, Y-type optical fiber (502) includes a common end connected to the end face of the electrode opposite to the catalyst layer (300), and two branch ends communicatively connected to the common end; The two branches are respectively connected to the second laser source (501) and the fluorescence spectrometer (503).

9. The system for in-situ monitoring of CO2 concentration and pH based on spectroscopic methods as described in claim 8, characterized in that: The fluorescence spectroscopy module (500) also includes, The fiber microneedle (504) has its end aligned with the common end of the Y-type fiber (502), and the distance between the end of the fiber microneedle (504) and the electrode surface is adjustable, with an adjustment range of 0.01 mm to 10 mm.

10. The system for in-situ monitoring of CO2 concentration and pH based on spectroscopic methods as described in claim 9, characterized in that: The common end of the Y-shaped optical fiber (502) is perpendicular to the electrode surface via the optical fiber microneedle (504).

11. A method for in-situ monitoring of CO2 concentration and pH based on spectroscopic methods, characterized in that: The following steps are included: The electrode according to any one of claims 1 to 5 is provided and placed in the reaction environment as a working electrode; Raman scattering spectra were collected from one side of the catalyst layer (300) of the electrode, and the HCO3 in the obtained Raman spectra were analyzed. - With CO3 2- Based on the characteristic peak information, the local pH value near the electrode is calculated; Fluorescence emission spectra are simultaneously collected from one side of the gas diffusion layer (100) of the electrode, and the local CO2 concentration near the electrode is calculated by analyzing the obtained fluorescence spectrum signals.

12. The method for in-situ monitoring of CO2 concentration and pH based on spectroscopic methods as described in claim 11, characterized in that: The calculated local pH value near the electrode includes, The formula for calculating the local pH value is: ; Where Ka is HCO3 - The dissociation constant, [CO3] 2- ] / [HCO3 - [CO3] 2- Ions and HCO3 - The concentration ratio of ions.

13. The method for in-situ monitoring of CO2 concentration and pH based on spectroscopic methods as described in claim 11 or 12, characterized in that: It also includes a calibration step that precedes the operation steps: Establish HCO3 by using several sets of mixed solutions of KHCO3 and K2CO3 with known pH values. - With CO3 2- Calibration curve between the Raman characteristic peak area ratio and pH value; By using several sets of calibration samples coated with the same fluorescent probe layer (200) under known CO2 concentration atmospheres, a calibration curve was established between the intensity of the characteristic fluorescent signal and the CO2 concentration.

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