PEMFC reversible attenuation on-line monitoring and recovery device and method

Abstract

The invention discloses a PEMFC reversible attenuation on-line monitoring and recovery device and method, the device comprises a parameter adjusting module, a controller, a multi-area detector and a battery, the parameter adjusting module, the controller and the multi-area detector are connected in sequence; the parameter adjusting module comprises an air compressor, a humidifier and a fan, a three-dimensional reversible attenuation model is arranged in the controller, the air compressor, the humidifier and the fan are respectively connected with the controller and the battery, and the battery is connected with the multi-area detector. Through the PEMFC three-dimensional reversible attenuation model, the ECSA and conductivity of different areas under different initial conditions and operation time are rapidly calculated, the PEMFC electrical performance is subjected to refined real-time detection and recovery, and the cost of refined detection is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a PEMFC reversible attenuation online monitoring and recovery device and method. Background Art

[0002] During long-term battery operation, all components of the membrane electrode assembly (MEA), including the membrane, electrodes, and gas diffusion layer, are susceptible to physical and chemical degradation, resulting in a continuous decline in proton exchange membrane fuel cell (PEMFC) performance over time, with performance too low to meet device requirements. Therefore, the battery requires a recovery device to recover from the effects of degradation and keep the battery performance within an appropriate range. In recent years, a large amount of research has been devoted to understanding and mitigating the effects of irreversible degradation. However, PEMFC degradation can be divided into irreversible degradation and reversible degradation. Reversible degradation accounts for approximately 65% ​​of the total performance degradation. Currently, most reversible degradation recovery methods use offline recovery, which requires shutting down the system and letting it rest overnight. This recovery method greatly restricts the continuity and reliability of PEMFC performance output. Therefore, it is necessary to design a method that can achieve online recovery of reversible degradation by adjusting external operating conditions during PEMFC use.

[0003] The prior art discloses a fuel cell stack performance recovery method and system, comprising an air inlet line, a chemical filter, an air compressor, an intercooler, a humidifier, a fuel cell stack, an air outlet line, a three-way valve, and an air return line. The device provides an internal air circulation system for the fuel cell stack's cathodes and detects the voltage of the fuel cell stack's output cells. When the fuel cell stack is in a performance recovery state, the internal air circulation system is activated. When the cell voltage is detected to be below a first threshold voltage, the fuel cell stack switches to a normal operating state. When the fuel cell stack is in a normal operating state, the internal air circulation system is stopped. When the cell voltage is detected to be above a second threshold voltage, the fuel cell stack switches to a performance recovery state. While this device can quickly and efficiently restore fuel cell stack performance, it cannot guarantee the rationality of fuel cell recovery. To address the issue of non-uniform attenuation, further refinement of the worst-case region is required.

[0004] The prior art also discloses a fuel cell recovery method. This method obtains a fuel cell reference voltage, controls the fuel cell to operate at a first preset current density and a first preset voltage for a first preset time, reduces the cathode stoichiometric ratio to a preset cathode stoichiometric ratio to achieve an oxygen-deficient state, operates the fuel cell at a second preset current density and oxygen-deficient state for a second preset time, measures a target voltage after the fuel cell has operated for the second preset time, and compares the reference voltage with the target voltage to generate a fuel cell recovery result. This fuel cell recovery method can recover various reversible degradation states in a fuel cell using available reactants in the fuel cell system without the need for additional piping control systems or inert gases. While this device can recover various reversible degradation states, it still cannot precisely adjust the worst-case region for non-uniform degradation.

[0005] Because PEMFC exhibits spatially non-uniform reversible decay characteristics, the electrochemically active surface area and conductivity vary significantly from inlet to outlet, leading to performance degradation. Online monitoring and recovery of reversible decay can restore reversible decay during PEMFC operation, facilitating long-term operation and improving operating life. Currently, there is a lack of online, refined monitoring and recovery methods for PEMFC reversible decay. To ensure that different regions of the PEMFC achieve their target performance, real-time, refined monitoring of each region is necessary.

[0006] In summary, existing fuel cell recovery devices and methods generally fail to account for the heterogeneity of performance degradation and recovery across different regions of the battery. These differences significantly impact the overall performance and safety of the battery. Furthermore, existing methods for monitoring and controlling different regions of the battery are complex and costly. Therefore, there is an urgent need to design a method and system that can effectively and precisely monitor and restore the performance of different regions of the battery, ensuring that the performance of different regions remains relatively consistent and improving the overall performance and safety of the battery. Summary of the Invention

[0007] To solve the technical problems existing in the above-mentioned prior art, the present invention proposes an online monitoring and recovery device and method for PEMFC reversible attenuation. Through the three-dimensional reversible attenuation model of PEMFC, the performance of different regions and times is predicted, the battery performance is restored in real time, and the refined detection and recovery of the battery is realized.

[0008] On the one hand, to achieve the above-mentioned object, the present invention provides a PEMFC reversible attenuation online monitoring and recovery device, comprising:

[0009] A parameter adjustment module, a controller, a multi-region detector and a battery, wherein the parameter adjustment module, the controller and the multi-region detector are connected in sequence;

[0010] The parameter adjustment module includes an air compressor, a humidifier and a fan. The controller has a built-in three-dimensional reversible attenuation model. The air compressor, humidifier and fan are respectively connected to the controller and the battery. The battery is connected to the multi-zone detector.

[0011] Preferably, the multi-region detector is used to collect the initial ECSA and initial conductivity, and the multi-region detector includes a cathode bipolar plate CBP, an air flow channel AFC, a cathode gas diffusion layer CGDL, a cathode microporous layer CMPL, a cathode catalyst layer CCL, a proton exchange membrane PEM, an anode catalyst layer ACL, an anode microporous layer AMPL, an anode gas diffusion layer AGDL, a hydrogen flow channel HFC and an anode bipolar plate ABP arranged in sequence.

[0012] On the other hand, to achieve the above-mentioned object, the present invention further provides a method for online monitoring and recovery of PEMFC reversible degradation, comprising:

[0013] S1. Collecting the initial electrochemically active specific surface area (ECSA), initial conductivity, and initial operating parameters of each region of the battery in an initial state through a multi-region detector, wherein the initial operating parameters include the humidity, excess ratio, and stack temperature of the battery;

[0014] S2, real-time calculation of ECSA and conductivity of different regions in the multi-region detector;

[0015] S3. Calculate the ECSA performance difference and the conductivity performance difference. When the ECSA performance difference or the conductivity performance difference of any area in the multi-area detector reaches a preset threshold or the battery is shut down, query the preset map table obtained by the model to obtain the recovery parameter;

[0016] S4. Regulating the air compressor, humidifier, and fan through a controller to adjust the initial operating parameters to the recovery parameters and operate within a preset time range;

[0017] S5. Re-test the ECSA and conductivity of each area. If the ratio of the ECSA and conductivity to the initial ECSA and initial conductivity does not reach the preset ratio, repeat S4-S5 until the standards are met.

[0018] Preferably, the conductivity is calculated using a three-dimensional reversible decay model, specifically:

[0019]

[0020] Where, χ rev represents the adsorption coefficient of sulfonate ionomer on platinum; χ irrev represents the irreversible attenuation loss coefficient of proton conductivity; λ represents the water content; σ l represents the electrolyte conductivity, T refis the reference temperature and T is the temperature.

[0021] Preferably, the ECSA is calculated by the three-dimensional reversible decay model as follows:

[0022]

[0023]

[0024] Where θ rev represents the coverage of the sulfonate catalyst, θ irrev represents the irreversible loss of catalyst active sites, is the attenuation coefficient of ECSA, A is the effective area, and A0 is the initial effective area of ​​ECSA.

[0025] Preferably, the attenuation coefficient of the ECSA is corrected by the coverage of the sulfonate catalyst, comprising:

[0026]

[0027] Where k s is the adsorption rate coefficient; ω s is the sulfonate adsorption interaction energy; Γ SCF is the maximum surface concentration of adsorption; S θ is the adsorption source term, F is the Faraday constant, t is the time, R is the universal gas constant, T is the temperature, η act,ca is the cathode activation overpotential.

[0028] Preferably, the three-dimensional reversible decay model is a non-isothermal two-phase multi-physics field model, wherein the proton transfer equation of the cathode catalyst layer CCL is:

[0029]

[0030] The electron transport equation is:

[0031]

[0032] Where, σ l represents the electrolyte conductivity; σ s Represents the electrode conductivity; ε CL represents the porosity of CCL; J ca represents the cathode electrochemical reaction rate of the aggregate; φ l represents the electrolyte potential; φ s Represents the electrode potential.

[0033] Compared with the prior art, the present invention has the following advantages and technical effects:

[0034] The present invention uses a three-dimensional reversible attenuation model of PEMFC to quickly calculate the ECSA and conductivity of different regions under different initial conditions and operating times, and performs refined real-time detection and recovery of PEMFC electrical performance, greatly reducing the cost of refined detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of this application. The exemplary embodiments and descriptions of this application are intended to explain this application and do not constitute an improper limitation on this application. In the accompanying drawings:

[0036] Figure 1 This is a schematic structural diagram of a PEMFC reversible attenuation online monitoring and recovery device according to an embodiment of the present invention;

[0037] Figure 2 Schematic diagram of the structure of a multi-region detector according to an embodiment of the present invention;

[0038] Figure 3 This is a flow chart of a method for online monitoring and recovery of PEMFC reversible degradation according to an embodiment of the present invention;

[0039] Figure 4 Schematic diagram of real-time conductivity recovery of PEMFC according to an embodiment of the present invention;

[0040] Figure 5 Schematic diagram of real-time ECSA recovery of PEMFC according to an embodiment of the present invention;

[0041] Figure 6 This is an example diagram of a query map representation according to an embodiment of the present invention;

[0042] Among them, 1-three-dimensional reversible attenuation model, 2-controller, 3-air compressor, 4-humidifier, 5-fan, 6-battery, 7-multi-zone detector. DETAILED DESCRIPTION

[0043] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0044] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0045] This embodiment proposes a PEMFC reversible decay online monitoring and recovery device, such as Figure 1 ,include:

[0046] A parameter adjustment module, a controller 2, a multi-region detector 7 and a battery 6, wherein the parameter adjustment module, the controller 2 and the multi-region detector 7 are connected in sequence;

[0047] The parameter adjustment module includes an air compressor 3, a humidifier 4 and a fan 5. The controller 2 has a built-in three-dimensional reversible attenuation model 1. The air compressor 3, the humidifier 4 and the fan 5 are respectively connected to the controller 2 and the battery 6. The battery 6 is connected to the multi-zone detector 7.

[0048] Furthermore, the multi-region detector 7 is used to collect the initial ECSA and initial conductivity, and the multi-region detector includes a cathode bipolar plate CBP, an air flow channel AFC, a cathode gas diffusion layer CGDL, a cathode microporous layer CMPL, a cathode catalyst layer CCL, a proton exchange membrane PEM, an anode catalyst layer ACL, an anode microporous layer AMPL, an anode gas diffusion layer AGDL, a hydrogen flow channel HFC and an anode bipolar plate ABP arranged in sequence, as shown in FIG. Figure 2 CGDL, CMPL, CCL, ACL, AMPL, and AGDL are considered isotropic and homogeneous. In AFC and HFC, the gas phase remains laminar. The irreversible decay model is replaced by experimental results from durability tests. The open circuit voltage loss is caused by parasitic electrochemical oxidation reactions introduced by hydrogen crossover. At the beginning of each operating cycle, there is no reversible decay. Only the reversible decay of ionomers is considered.

[0049] This embodiment also provides a method for online monitoring and recovery of PEMFC reversible degradation, such as Figure 3 ,include:

[0050] S1. Collecting the initial electrochemically active specific surface area (ECSA), initial conductivity, and initial operating parameters of each region of the battery 6 in an initial state through a multi-region detector 7, wherein the initial operating parameters include the battery's humidity, excess ratio, and stack temperature;

[0051] S2, real-time calculation of ECSA and conductivity of different regions in the multi-region detector 7;

[0052] S3. Calculate the ECSA performance difference and conductivity performance difference respectively by subtracting the real-time ECSA or conductivity calculated in the model from the initial ECSA or initial conductivity data. When the ECSA performance difference or conductivity performance difference of any area in the multi-area detector 7 reaches a preset threshold or the battery is shut down, query the preset map table obtained by the model to obtain the recovery parameters, such as Figure 6 ;

[0053] S4, regulating the air compressor 3, the humidifier 4 and the fan 5 through the controller 2, adjusting the initial operating parameters to the recovery parameters and operating within a preset time range;

[0054] S5. Re-test the ECSA and conductivity of each area. If the ratio of the ECSA and conductivity to the initial ECSA and initial conductivity does not reach the preset ratio, repeat S4-S5 until the standards are met.

[0055] This example establishes a three-dimensional reversible decay model, using the initial ECSA and conductivity, along with operating parameters and time t, as model inputs. The real-time electrochemically active area (ECSA) and conductivity of each region are calculated and the difference from the initial performance is evaluated. When the performance difference is greater than 50%, the following recovery parameters are obtained by querying a map: humidity AH', excess ratio λ', and stack temperature T'. After 30 minutes of recovery, if the initial ratio of the electrochemically active area (ECSA) and conductivity reaches 80%, performance recovery is considered to have met the requirements. Otherwise, performance recovery is considered to have failed to meet the requirements and further recovery or replacement is required.

[0056] Furthermore, the conductivity is calculated using a three-dimensional reversible decay model, specifically:

[0057]

[0058] Where, χ rev represents the adsorption coefficient of sulfonate ionomer on platinum; χ irrev represents the irreversible attenuation loss coefficient of proton conductivity; λ represents the water content; σ l represents the electrolyte conductivity, T ref is the reference temperature and T is the temperature.

[0059] Specifically, the real-time conductivity and ECSA during the use of PEMFC are calculated by the three-dimensional reversible decay model. The schematic diagram of the reversible decay regulation is as follows: Figure 4 and Figure 5 shown.

[0060] The three-dimensional reversible decay model is a non-isothermal, two-phase, multiphysics model. The fundamental modeling theory of this multiphysics model includes conservation of mass, momentum, and energy; gas, liquid water, and ionized water content; and proton and electron transport. This example focuses on proton and electron transport in the decay scenario.

[0061] Among them, the proton transfer equation of the cathode catalyst layer CCL is:

[0062]

[0063] The electron transport equation is:

[0064]

[0065] Where, σ l represents the electrolyte conductivity; σ sRepresents the electrode conductivity; ε CL represents the porosity of CCL; J ca represents the cathode electrochemical reaction rate of the aggregate; φ l represents the electrolyte potential; φ s Represents the electrode potential.

[0066] Cathodic electrochemical reaction rate J of aggregates ca Determined by the following formula:

[0067]

[0068] Where F is the Faraday constant, represents the oxygen concentration on the catalyst surface, and k represents the electrochemical reaction rate constant considering ECSA degradation, which is expressed by the Butlerk-Volmer equation:

[0069]

[0070] Where a ca represents the theoretical maximum ECSA; represents the ECSA attenuation coefficient; represents the cathode reference current density; θ PtO represents the proportion of platinum oxide; Indicates the reference oxygen concentration; represents the activation energy of the cathode electrochemical reaction; R is the universal gas constant; T is the temperature; T ref is the reference temperature; α ca represents the charge transfer coefficient; η act,ca represents the cathode activation overpotential.

[0071] Furthermore, the ECSA is calculated by the three-dimensional reversible decay model as follows:

[0072]

[0073] Where θ rev represents the coverage of the sulfonate catalyst, θ irrev represents the irreversible loss of catalyst active sites, is the attenuation coefficient of ECSA, A is the effective area, and A0 is the initial effective area of ​​ECSA.

[0074] Specifically, as the operating time increases, the proton transport resistance increases due to irreversible decay and reversible decay. Therefore, the corrected proton conductivity based on the Springer equation is determined by the following formula:

[0075]

[0076] Where, χ revrepresents the adsorption coefficient of sulfonate ionomer on platinum; χ irrev represents the coefficient of irreversible decay loss of proton conductivity; λ represents the water content, defined as the number of water molecules per sulfonic acid group in CCL, ACL, and PEM.

[0077] Under low humidity conditions, due to insufficient water, a large number of platinum sites preferentially adsorb to the sulfonic acid groups on the side chain of the ionomer rather than the hydrated hydrogen ion, resulting in poisoned platinum sites that not only reduce the effective surface area of the catalyst but also hinder the proton transport path, thereby increasing the local oxygen transport resistance and proton transport resistance.

[0078] In summary, the present embodiment considers two key effects of ionomer sulfonic acid group adsorption mechanism on platinum in the reversible decay process: (1) reduction of ECSA; (2) increase of proton transport resistance.

[0079] Further, the degree of adsorption of ionomer sulfonate on platinum is described by the catalyst coverage of sulfonate, which is determined by the following formula:

[0080]

[0081] where k s is the adsorption rate coefficient, ω s is the sulfonate adsorption interaction energy, Γ SCF is the maximum surface concentration of adsorption, F is the Faraday constant, t is time, R is the universal gas constant, T is temperature, η act，ca is the cathode activation overpotential, S θ is the adsorption source term, determined by the following equation:

[0082]

[0083] where k θ is the adsorption rate coefficient determined by current density and temperature; λ0 is the initial water content; T0 is the initial temperature.

[0084] The semi-empirical equation a ECSA for ECSA is as follows:

[0085]

[0086] where b is the fitting coefficient; E a is the activation energy.

[0087] The adsorption coefficient of ionomer sulfonate on platinum is corrected by the catalyst coverage of sulfonate:

[0088] χ rev = 1 - θ rev .

[0089] Set the mass flow rate and mole fraction as the inlet boundary conditions, and set P ca 、 out and P an 、 out Set as the outlet boundary condition, refer to the operating conditions in Table 1, and determine the mass flow rate and mole fraction using the following formula:

[0090]

[0091]

[0092] Where A represents the active area; is the molar mass of hydrogen; is the molar mass of water; is the molar mass of oxygen; is the molar mass of nitrogen; represents the mole fraction of feed hydrogen; and are the feed water mole fractions at the anode and cathode, respectively; p sat represents the saturated vapor pressure; p an,in and p ca,in Represent the feed pressure of anode and cathode respectively, m an，in and m ca，in are the gas mass flow rates at the anode and cathode, ξ an and ξ ca are the excess ratios of the anode and cathode, RH an,in and RH ca,in are the humidity of the anode and cathode, T st For temperature.

[0093] Table 1

[0094]

[0095] In addition, the irreversible boundary conditions are obtained from experimental results, including the irreversible loss of catalyst active sites θ irrev , irreversible attenuation loss coefficient of proton conductivity χ irrev and hydrogen cross.

[0096] The current density boundary condition is determined by the set current density load and hydrogen crossover:

[0097] i b =ii cross ,

[0098]

[0099] Where i cross Indicates hydrogen crossover; β irrevrepresents the irreversible attenuation coefficient of hydrogen crossover; represents the hydrogen permeability coefficient; Indicates the hydrogen pressure at the anode; δ m represents the thickness of the proton exchange membrane; represents the activation energy of hydrogen diffusion, i b is the current density boundary condition, and i is the experimental current density.

[0100] This embodiment uses the initial state parameters ECSA and conductivity measured by the device in different regions. These initial ECAS and conductivity, along with operating parameters, serve as inputs for a three-dimensional reversible decay model. This model rapidly calculates the real-time ECSA and conductivity of each region and assesses the performance difference from the initial value. When the performance difference exceeds 50%, a map is queried to obtain recovery parameters. Performance is then restored until the required ECAS and conductivity are restored to 80% of the initial values. This technical solution provides a precise and timely method for detecting recovery in PEMFCs.

[0101] The above are merely preferred embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A PEMFC reversible decay online monitoring and recovery device, characterized in that: include: A parameter adjustment module, a controller (2), a multi-region detector (7) and a battery (6), wherein the parameter adjustment module, the controller (2) and the multi-region detector (7) are connected in sequence; The parameter adjustment module includes an air compressor (3), a humidifier (4) and a fan (5); the controller (2) has a built-in three-dimensional reversible attenuation model (1); the air compressor (3), the humidifier (4) and the fan (5) are respectively connected to the controller (2) and the battery (6); and the battery (6) is connected to the multi-region detector (7).

2. The PEMFC reversible decay online monitoring and recovery device according to claim 1, characterized in that: The multi-region detector (7) is used to collect initial ECSA and initial conductivity, and the multi-region detector (7) includes a cathode bipolar plate CBP, an airflow channel AFC, a cathode gas diffusion layer CGDL, a cathode microporous layer CMPL, a cathode catalyst layer CCL, a proton exchange membrane PEM, an anode catalyst layer ACL, an anode microporous layer AMPL, an anode gas diffusion layer AGDL, a hydrogen flow channel HFC and an anode bipolar plate ABP arranged in sequence.

3. A method for online monitoring and recovery of PEMFC reversible degradation according to any one of claims 1 to 2, characterized in that: include: S1, collecting the initial electrochemically active specific surface area ECSA, initial conductivity and initial operating parameters of each region of the battery (6) in the initial state through a multi-region detector (7), wherein the initial operating parameters include the humidity, excess ratio and stack temperature of the battery; S2, real-time calculation of ECSA and conductivity of different regions in the multi-region detector (7); S3, respectively calculating the ECSA performance difference and the conductivity performance difference, and when the ECSA performance difference or the conductivity performance difference of any area in the multi-area detector (7) reaches a preset threshold or the battery is shut down, querying the preset map table obtained by the model to obtain the recovery parameter; S4, regulating the air compressor (3), the humidifier (4) and the fan (5) through the controller (2), adjusting the initial operating parameters to the recovery parameters and operating within a preset time range; S5. Re-test the ECSA and conductivity of each area. If the ratio of the ECSA and conductivity to the initial ECSA and initial conductivity does not reach the preset ratio, repeat S4-S5 until the standards are met.

4. The method according to claim 3, characterized in that The conductivity is calculated by a three-dimensional reversible decay model, specifically: Where, χ rev represents the adsorption coefficient of sulfonate ionomer on platinum; χ irrev represents the irreversible attenuation loss coefficient of proton conductivity; λ represents the water content; σ l represents the electrolyte conductivity, T ref is the reference temperature and T is the temperature.

5. The method according to claim 4, characterized in that The ECSA is calculated by the three-dimensional reversible decay model as: Where θ rev represents the coverage of the sulfonate catalyst, θ irrev represents the irreversible loss of catalyst active sites, is the attenuation coefficient of ECSA, A is the effective area, and A0 is the initial effective area of ​​ECSA.

6. The method according to claim 4 or 5, characterized in that The ECSA attenuation coefficient is corrected by the coverage of the sulfonate catalyst, including: Where k s is the adsorption rate coefficient; ω s is the sulfonate adsorption interaction energy; Γ SCF is the maximum surface concentration of adsorption; S θ is the adsorption source term, F is the Faraday constant, t is the time, R is the universal gas constant, T is the temperature, η act,ca is the cathode activation overpotential.

7. The method according to claim 3, characterized in that The three-dimensional reversible decay model is a non-isothermal two-phase multi-physics field model, in which the proton transfer equation of the cathode catalyst layer CCL is: The electron transport equation is: ▽(-s s ▽φ s )=J ca , Where, σ l represents the electrolyte conductivity; σ s Represents the electrode conductivity; ε CL represents the porosity of CCL; J ca represents the cathode electrochemical reaction rate of the aggregate; φ l represents the electrolyte potential; φ s Represents the electrode potential.

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