Method for determining a contamination of components for electrochemical cells by means of fluorescence and corresponding measuring device

Abstract

The invention relates to a method for determining a contamination (1) of components for electrochemical cells, in particular components for water electrolysis, by means of fluorescence. The method comprises (S1) providing a component sample (2) for measuring the contamination, (S2) exciting the component sample (2) with fluorescence radiation, (S3) detecting the fluorescence generated by the excitation, and (S4) inferring an amount of contamination (1) of the component sample (2) from a recorded fluorescence signal (3), wherein a signal strength of the recorded fluorescence signal (3) is correlated with a correlation parameter (s) in order to verify the purity of the component sample (2). The invention further relates to the use of a fluorescence measurement and to a corresponding measuring device (20) for carrying out the method.

Description

[0001] 2024PF00053

[0002] 1

[0003] Description

[0004] Method for determining contamination on components for electrochemical cells using fluorescence and corresponding measuring device

[0005] The present invention relates to a method for determining, measuring, or quantifying impurities in components for electrochemical cells, particularly for water electrolysis, using fluorescence. In other words, a corresponding method for quality assurance or for determining the purity of components for water electrolysis or comparable components, such as fuel cells, is provided. In yet other words, the present invention relates to the use of the fluorescence method for the corresponding determination of purity or impurities, particularly on an automated or industrial scale.

[0006] The components to be tested for purity are preferably bipolar plates, gas diffusion layers, so-called porous transport layers, carbon or metal fleeces, membranes such as PEM membranes (PEM) or anion exchange membranes (AEM), entire membrane electrode assemblies, diaphragms, parts of these components, or combinations of these components.

[0007] In current and future energy technologies, electrochemical cells, such as PEM fuel cells and electrolysis concepts, are gaining increasing importance for sustainable energy systems and industrial processes, driven by the energy transition. For example, PEM electrolysis (PEM stands for "polymer electrolyte membrane" or "proton exchange membrane") is becoming increasingly relevant in the industrial production of green hydrogen from renewable energy sources, or as an energy carrier, for example, for industrial applications or as a storage medium, due in part to its partial load capability. In the context of climate change, hydrogen (H2) and / or the possibility of producing H2 from renewable energy via PEM or water electrolysis has long since proven to be a key factor for the energy industry and related sectors.Even though most hydrogen is still produced conventionally today, for example through steam reforming of methane or coal gasification, aggressive investments and support measures are expected to bring about a clear trend towards renewable hydrogen production.

[0008] In a PEM electrolysis cell, a membrane is provided with a catalyst layer on opposite surfaces. These catalyst layers are typically bordered by gas diffusion layers, which in turn are connected to electrically conductive contact plates, also known as bipolar plates, serving, among other things, for electrical contact. Preferably, the gas diffusion layers are designed to enable the necessary substance transport during the intended operation of the electrolysis cell. The gas diffusion layer thus provides the required electrical conductivity to couple the contact plates and the catalyst layers. This allows the desired electrochemical reaction to occur within the catalyst layers.

[0009] Sufficient purity of the bipolar plates and GDL materials is essential for the industrialized production of water electrolyzers or fuel cells, as well as for their economical manufacture and distribution, particularly to improve the functionality of the membrane electrode assembly and reduce the costs of the PEMWE system. The purity of the components can be equally crucial for their service life. The fewer residues or impurities found on the (metallic) components, the less dirt will accumulate on the membrane.

[0010] Membrane electrode arrangement. As a result, the complex and valuable cell materials, especially catalyst and membrane materials, degrade less, and their lifespan and operational capability increase accordingly. Ultimately, this makes cell manufacturing more sustainable and reduces the dependence of operators and manufacturers of corresponding energy systems on scarce raw materials.

[0011] Furthermore, it is very important that the components on the anode side meet the high cleanliness requirements regarding organic residues for oxygen applications.

[0012] The electrolysis cells are typically connected in series in so-called stacks. An electrolyzer usually has a large number of these stacks.

[0013] According to the state of the art, the gas diffusion layers are realized as expanded metal, perforated sheet metal, wire mesh, wire fabric, wire knitting, pressed wire or rigid, embossed plates, onto which a metal- or carbon-based fiber fleece may be laid.

[0014] In PEM electrolysis systems, among other applications, the purity of the components is extremely important. Contamination of components can, when installed in the electrolysis cells, directly reduce the proton conductivity of the membrane; this occurs particularly through the occupation of sulfonic acid groups with polyvalent cations (e.g., Na). + , Ca 2+or others). Furthermore, contaminants can lead to material reactions in metallic cell components, such as metal oxidation, and thus also to membrane degradation. Therefore, highly purified, deionized (fully demineralized) water is used as the reactant for water electrolysis. Additionally, all components used (bipolar plate, GDLs, transport layers, fleeces, membranes, etc.) must be

[0015] Membrane electrode components) must be cleaned and free of oil, grease, dust, and other contaminants. Purity (especially with regard to oil and grease) is particularly important on the anode side of the cell for safety reasons due to contact with the pure oxygen produced.

[0016] The parts must be specially cleaned with cleaning agents and purified water before installation. Even if the surface appears visually clean, techniques must be used to verify its purity. Conventionally, this is achieved, for example, by measuring the surface tension of a test solution (indicator) as a measure of the degree of filmic contamination. The surface tension should be above a certain value (threshold) to classify the surface as clean.

[0017] PEM electrolysis is mentioned here only as an example of one possible application area of ​​the invention. The suitability and advantages of the invention apply without limitation to other electrolysis technologies, such as AEL (alkaline electrolysis) or AEM (anion exchange membrane) electrolysis. Furthermore, the presented solution for the determination of impurities by means of correlation and fluorescence may even be suitable for unrelated technical fields.

[0018] Surface tension is typically determined using a test ink. However, this ink test for determining surface tension, and thus surface cleanliness, has disadvantages. These include the high manual effort required, as each test must be carried out and evaluated manually in a time-consuming (individual) manner.

[0019] Furthermore, the parts are contaminated with the test ink after the test and must be cleaned again, which is detrimental. In addition, the indicator ink is a consumable and therefore incurs ongoing costs, especially since the ink has a limited lifespan, typically only six months.

[0020] Furthermore, the evaluation of these tests can be ambiguous or inconclusive. Typically, the aforementioned ink can only partially and relatively indicate surface cleanliness, thus only indicating whether the surface tension is greater or less than a specific value.

[0021] Furthermore, only random quality tests are possible, which cannot be incorporated into regular or continuous quality control. Finally, the "ink tests" are only possible locally, not across large areas of the component. This aspect, in particular, disqualifies conventional tests as part of industrialized quality assurance for water electrolysis or electrochemical cell components.

[0022] Furthermore, detecting contamination at the customer's site has so far proven to be very time-consuming or difficult, as photographic documentation is hampered by the short observation time of the ink (only about 4 seconds).

[0023] Furthermore, very fine 3D structures cannot be measured at all because the test ink, due to its geometry, cannot form an uninterrupted stripe, even if a value of the surface tension would actually be sufficient.

[0024] Another significant disadvantage of these tests is the influence of temperature on the test result, with the surface tension decreasing by approximately 1 mN / m for every 10 °C temperature increase.

[0025] It is therefore an object of the present invention to offer a solution that solves the aforementioned problems. In particular, a method for determining impurities is provided which is more accurate, more reliable, and significantly better suited for automated, industrialized quality assurance.

[0026] This problem is solved by the subject matter of the independent patent claims. Advantageous embodiments are the subject matter of the dependent patent claims.

[0027] One aspect of the present invention relates to a method for determining, measuring, or quantifying an impurity on electrolysis components by means of fluorescence.

[0028] The procedure involves providing a component sample, for example a calibration sample, to measure the contamination or to determine the cleanliness of the component.

[0029] The process also includes excitation of the component sample with fluorescence radiation, such as fluorescent light, light from a UV lamp or a laser.

[0030] The method further includes detecting the fluorescence generated by the excitation and inferring from a recorded or detected fluorescence signal to an amount of contamination or corresponding loading of the component sample.

[0031] According to one embodiment, contamination refers to residues or remnants of cleaning agents, oil, grease, coolants, and / or lubricants. Furthermore, marking residues, wash water, indicators, or ink residues can also act as contaminants. These or other contaminants not explicitly mentioned here are likely to occur during the preparation, manufacturing, assembly, installation, or final assembly of electrolysis cells and are therefore potentially relevant to quality.

[0032] The increasingly industrialized production of green, electrolytically generated hydrogen necessitates, in this context, improved and more reliable methods for determining component purity. In other words, the invention relates to a fluorescence method for measuring the cleanliness of such components.

[0033] This allows the aforementioned disadvantages to be avoided and further new advantages to be exploited.

[0034] With the present invention, for example, no manual effort is required. Instead, the corresponding test can be carried out and / or evaluated automatically or semi-automatically.

[0035] The components are advantageously not contaminated by the fluorescence test according to the invention and therefore do not need to be cleaned again.

[0036] There are also no expensive consumables involved.

[0037] Furthermore, a corresponding fluorescence signal can be clearly evaluated, allowing conclusions to be drawn about the underlying amount of contamination in the component sample.

[0038] A further advantage of the invention is that a corresponding fluorescence test can be performed "inline" or serially during the production of the electrolysis components. This enables 100% testing and quality assurance of the components.

[0039] Furthermore, even very fine impurities on complex component structures can be detected sensitively, selectively and across the entire component (not just locally).

[0040] In one embodiment, the component or component sample comprises a bipolar plate, a gas diffusion layer, a so-called porous transport layer, a metal fleece, a membrane such as a PEM, a diaphragm, a membrane electrode assembly, parts, or combinations of these components. For example, bipolar plates and gas diffusion layers can be in prefabricated and / or welded form. According to alternative embodiments, the invention also allows for the examination of components used only in the periphery or in the "balancing" of electrochemical cells, such as pipelines, heat exchangers, gas separators, or similar components, for impurities using the presented approach and for determining the degree of purity accordingly.If similar requirements for components arise in more distant technical fields, such as electrochemistry, electrolysis or the operation of fuel cells, the application of the presented method can, in principle, also extend to such neighboring technology fields.

[0041] In one embodiment, the component is metallic or has a metallic surface. Accordingly, the component can particularly include bipolar plates, so-called gas diffusion layers, or corresponding metal tiles for electrolyzers, which, due to their prefabrication, are often contaminated with oil or grease residues, for example, residues of cutting oil or similar substances.

[0042] In one embodiment, the component has an interwoven or intertwined, complex or three-dimensional structure, such as in the case of wire or metal meshes or "metal knits" for gas diffusion layers. Such complex (non-flat) and difficult-to-access surfaces significantly complicate, for example, measuring surface tension using a suitable ink test, making it nearly impossible to determine the degree of contamination on them reliably or reproducibly.

[0043] According to one embodiment, the described method involves correlating the signal strength of the recorded fluorescence signal with a correlation parameter (e.g., known, measured, or to be measured), such as the surface tension of a test solution, wetting, or the contact angle of a corresponding solvent (test ink), in order to quantify the purity of the component sample or the level of contamination. According to this embodiment, the correlation can be part of the process of inferring the amount of contamination in the component sample from the recorded fluorescence signal. In particular, this correlation is advantageously achieved by enabling reliable purity measurements of even inaccessible or complex component geometries, such as the aforementioned complex 3D structures.

[0044] In one embodiment, a flat or quasi-two-dimensional component sample with a defined level of contamination or contamination is used for correlation. A limit value or purity threshold for the correlation parameter, such as surface tension, can then be derived for determining the level of contamination. This threshold defines the point at which the component can still be considered sufficiently clean for further processing. In other words, this two-dimensional component sample can also be used to transfer the measurement from 2D to 3D.

[0045] Subsequently, an equivalent impurity, for example, one that is equivalent and has the same effect as the defined impurity, is applied to a three-dimensional structure corresponding to the component sample, and the resulting fluorescence signal is evaluated. In this way, a correlation between surface tension and the fluorescence signal can be established more advantageously for a three-dimensional structure without actually being able to, or having to, measure the aforementioned correlation parameter for the 3D structure.

[0046] According to one embodiment, the defined contamination represents a defined loading of the component sample with a cutting oil or a cleaning agent. In a specific embodiment, the correlation parameter is a surface tension or wettability of the component sample, which is determined for calibration using a test ink or another alternative method (such as wiping and weighing contaminants).

[0047] According to a suitable embodiment, the component sample is excited with ultraviolet light, for example with light of a specific wavelength, and / or by means of a laser, and the corresponding fluorescence radiation is then detected.

[0048] In a further embodiment, the fluorescence of the sample is detected using a fluorometer, a photon detector, a suitable camera, or a fluorescence microscope. This embodiment also allows for the appropriate use of the fluorescence method in the present context.

[0049] Another aspect of the present invention relates to the use of fluorescence measurement to determine the aforementioned impurities on three-dimensional components, as described above.

[0050] A further aspect of the present invention relates to a measuring arrangement or measuring device which is set up for carrying out the described method, comprising a fluorescence light source, in particular a laser or a source for the emission of ultraviolet light, and a fluorescence detector, such as a fluorometer, a photon detector, a camera or a fluorescence microscope.

[0051] Features, characteristics and / or advantages relating to the method or use described herein may also directly relate to the measuring device, or vice versa. The expression "and / or" or "or" used here, when used in a series of two or more elements, means that each of the listed elements may be used individually, or any combination of two or more of the listed elements may be used.

[0052] Further details of the invention are described below with reference to the figures.

[0053] Figure 1 illustrates the functionality of a PEM water electrolysis cell using a schematic sketch as an example and representative representation.

[0054] Figure 2 illustrates, by means of a schematic flowchart, the process steps according to the invention as well as other aspects of the present invention.

[0055] Figure 3 shows a part of a gas diffusion electrode as a component sample, with sufficient purity (see left part of figure a) and corresponding contamination (see right part of figure b).

[0056] Figure 4 shows four partial representations of fluorescence signals which are correlated to determine the contamination on a corresponding component sample.

[0057] In the exemplary embodiments and figures, identical or equivalent elements may be designated with the same reference numerals. The depicted elements and their relative sizes are generally not to be considered to scale; rather, individual elements may be exaggeratedly thick or large for clarity and / or better understanding.

[0058] Figure 1 shows an electrolysis cell 10, in particular a PEM electrolysis cell for water electrolysis. The core of such a polymer electrolyte membrane electrolysis cell 10 is formed by a membrane 11. The membrane 11 is coated or provided with catalysts 12.

[0059] The membrane 11, in particular PEM, is typically coated with a layer of a respective catalyst material on both the anode side (see left in Figure 1) and the cathode side (see right in Figure 1) on two surfaces facing away from each other. The respective cell reaction of electrolysis takes place in the region of the layer formed by the respective catalyst material.

[0060] During normal operation, electrons are transferred via the respective catalyst material and a support structure formed by the gas diffusion layer or layers 13 to the corresponding bipolar plate (see reference numeral 14). Furthermore, a proton flow H+ from left to right through the membrane 11 to the hydrogen cathode occurs, as indicated by the arrow in the center of the arrangement.

[0061] The membrane 11, or a starting material which is usually to be coated for the coating of the membrane 11 with the “catalyst”, usually contains a perfluorosulfonic acid (PFSA) material, polymer or ionomer.

[0062] It is further evident that reactant water (H2O) is generally provided on the anode side, which can be released and obtained by means of the electrolysis process when a direct voltage designated with the reference symbol DC is applied, in oxygen (O2) at the anode and hydrogen (H2) at the cathode (cf. right side of cell 10 in figure 1).

[0063] Figure 2 schematically illustrates a measuring device 20 for carrying out the method according to the invention, which is also only schematically indicated by means of a flowchart based on the process steps SI, S2, S3 and S4. The measuring device 20 is advantageously suited for carrying out the method according to the invention. This method enables the reliable and accurate determination of a contaminant 1 on components for water electrolysis by means of fluorescence, comprising providing (Sl) a component sample 2 for measuring the contaminant.

[0064] Furthermore, the procedure includes excitation (S2) of the component sample 2 with fluorescence radiation.

[0065] Furthermore, the procedure includes detecting (S3) the fluorescence generated by the excitation, and in step S4, inferring from the recorded fluorescence signal 3 a quantity of impurity 1 of the component sample 2.

[0066] In other words, the procedure describes the use of the fluorescence method for determining the contamination on the component.

[0067] Reference numeral 21 indicates a fluorescent light source with which the component sample 2 can be conveniently irradiated with ultraviolet light using the method described. Contrary to what is shown by pictogram 21, the fluorescent light source 21 can also be a monochromatic laser 21 for exciting the fluorescence (laser-induced fluorescence).

[0068] An evaluation unit or detector is designated by reference numeral 22, in particular a fluorometer, a photon detector, or a camera for recording the fluorescence signal.

[0069] Without limiting the generality of the experimental setup, spectral filters not explicitly identified here may also be used. In this method, the longer-wavelength fluorescence emission excited by the short-wavelength laser beam is expediently detected with pinpoint accuracy, whereby the backscattered excitation light from the light source 21 is detected, for example, by means of a

[0070] Filter arrangement in front of the detector allows filtering.

[0071] In other words, by measuring the fluorescence signal and correlating the signal strength with the surface tension, the cleanliness or purity of the corresponding components can be measured or verified.

[0072] A photon detector 22 or fluorometer is used as a measuring device, which measures the amount of light emitted by the sample 2 after it has absorbed light of a certain wavelength.

[0073] This allows fluorescent substances that also affect surface cleanliness to be detected, such as oil, cleaner, wash water, grease, fingerprints, label residues, test ink residues, or other similar substances.

[0074] Figure 3 shows, in two partial views, a component sample 2, which in particular represents a three-dimensional, complex metal grid or metal mesh, metal fabric or metal knit of a gas diffusion layer 13 for a water electrolysis cell 10. In the left partial view (a) a continuous test ink strip can be seen, which can be used to indicate the wettability or wettability of the test ink - depending on the surface tension of the component.

[0075] Figure 3a (left) shows a test with a clean component, and Figure 3b (right) shows a test with a contaminated component. If the surface tension of the test solution exceeds a certain value, the test ink 4 forms a continuous streak (see left in 3a), and the component surface is considered clean. Otherwise, the ink streak is interrupted after a very short time (see Figure 3b). The continuity of the ink streak in Figure 3a clearly indicates that the wettability is high; that is, the surface tension of the ink solution 4, which is free of contaminants, is higher than in the right-hand illustration (3b). In the right-hand image, it can be seen that the test ink streak 4 is interrupted or not continuous, but rather forms droplets and / or breaks.This is a sign that the surface tension s and also the wetting on component sample 2 is reduced compared to a clean surface, and that the component is dirty or contaminated with the substances mentioned above.

[0076] By producing flat samples with defined contamination and corresponding dirt loading, a relationship is advantageously established, for example, between the loading with the contaminants cutting oil and cleaning agents and the corresponding surface tensions. This relationship or correlation is particularly necessary to verify or determine the surface tension requirement or an upper limit (for example, measured in [mN / m]).

[0077] The same amount of impurity can then be applied to the 3D structure shown, and the fluorescence signal evaluated (see Figure 4, right). This allows a correlation between surface tension and the fluorescence signal 3 for a 3D structure to be established without actually measuring the surface tension of the 3D structure.

[0078] Preliminary tests using a UV lamp or laser as a fluorescence light source 21 and a corresponding detector 22 demonstrated that filmic contaminants on the component fluoresce and that there is a measurable correlation between the amount of contaminant (loading) and the recorded fluorescence signal (fluorescence intensity). Figure 4 shows the fluorescence signals of a cutting oil. The left-hand images, a) and c), each represent the result of a test or calibration sample; whereas the right-hand images, b) and d), show fluorescence signals of the (unknown) contaminant, which is difficult to measure using the indicator test, on a corresponding 3D structure.

[0079] In the partial illustration a) top left, a faint, interrupted test ink trace can be seen in the lower half, indicating that the component is impure or contaminated (see Figure 3 and the description above). The measured surface tension s here is less than 44 mN / m.

[0080] The value s of 44 mN / m can be considered in the present case as an example of the limit value described above, above which the component can be classified as sufficiently clean.

[0081] In partial representation b), the corresponding fluorescence signal for a three-dimensional or complex structure (as described above) is shown. The fluorescence contrast can correspond to that in partial representation a).

[0082] In the lower left of image C), an uninterrupted test indicator strip is visible, suggesting that the component can be classified as sufficiently clean. The measured surface tension s is greater than the limit of 44 mN / m. Here, and also in the lower right image d), there is hardly any noticeable fluorescence contrast, which, based on the described correlation, qualifies the fluorescence method as reliable and informative for determining the purity of the complex structure. It can generally be concluded that the fluorescence signal provides information about the strength of the corresponding impurity. Based on the fluorescence contrast of the investigated sample(s), it is evident that even small amounts of impurity on the sample cause a large difference in the measured fluorescence.Surface tension s can still be determined using common methods, such as force-based tensiometry or contact angle measurements. The Wilhelmy plate method or the Du-Noüy ring method are also possible and appropriate.

Claims

Patent claims 1. Method for determining a contamination (1) on components for electrochemical cells by means of fluorescence, comprising: - (Sl) Providing a component sample (2) for measuring the contamination, - (S2) Excitation of the component sample (2) with a fluorescence radiation, - (S3) Detecting the fluorescence produced by the excitation, and - (S4) Inference from a recorded fluorescence signal (3) to an amount of impurity (1) of the component sample (2) , wherein a signal strength of the recorded fluorescence signal (3) is correlated with a correlation parameter (s) to verify the purity of the component sample (2), wherein the component (2) is a bipolar plate (14), a gas diffusion layer (13), a porous transport layer, a metal fleece, a membrane (11), a diaphragm, a membrane electrode arrangement, parts or combinations of these components, and wherein the component (2) has an interwoven or woven, i.e., a three-dimensional structure.

2. Method according to claim 1, wherein the contaminant (1) is a cleaning agent, an oil and / or grease residue.

3. Method according to one of the preceding claims, wherein the component (2) is metallic.

4. A method according to one of the preceding claims, wherein a flat or quasi-two-dimensional component sample (2) with a defined impurity (1) is used for the correlation, wherein a limit value of the correlation parameter (s) is derived for the determination of the impurity (1), and wherein an equivalent impurity is subsequently applied to one of the component samples. The corresponding three-dimensional structure is applied, and the corresponding fluorescence signal (3) is evaluated.

5. Method according to claim 4, wherein the defined impurity (1) is a defined loading of the component sample (2) with a cutting oil or a cleaning agent .

6. Method according to one of the preceding claims, wherein the correlation parameter (s) is a surface tension which is determined by means of a test ink (4).

7. Method according to one of the preceding claims, wherein the component sample (2) is excited with ultraviolet light or by means of a laser (21).

8. Method according to one of the preceding claims, wherein the fluorescence of the sample is detected by means of a fluorometer (22), a photon detector, a camera or a fluorescence microscope.

9. Use of a fluorescence measurement for the determination of impurities (1) , in particular cleaning agents, oil or grease residue, on three-dimensional, in particular metallic, components for electrochemical cells, such as bipolar plates (14) , gas diffusion layers (13) , porous transport layers, metal fleeces, membranes (11) , membrane electrode arrangement, parts or combinations of these components .

10. Measuring arrangement (20) which is set up for carrying out the method according to one of the preceding claims or the use according to claim 9, comprising a fluorescence light source (21), in particular a laser or a source for the emission of ultraviolet light for exciting a component sample (2), and a fluorescence detector (22), such as a fluorometer, a photon detector, a camera or a fluorescence microscope.

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