Recycling of catalyst coated membrane components

Abstract

A method for recycling spent catalyst coated membranes, the spent catalyst coated membranes comprising a membrane comprising a membrane ionomer, a first catalyst layer disposed on one side of the membrane, the first catalyst layer comprising a first catalyst and a first catalyst layer ionomer, and a second catalyst layer disposed on an opposite side of the membrane, the second catalyst layer comprising a second catalyst and a second catalyst layer ionomer, The method is configured to recover the first and second catalyst layer ionomers in addition to the catalyst material and the membrane ionomer.

Description

[Technical Field]

[0001] This specification relates to a method for recycling components of catalyst coated membranes such as those used in fuel cells and hydrogen producing water electrolyzers. [Background technology]

[0002] As investments are made in the global hydrogen economy, the production of fuel cells and hydrogen-producing water electrolyzers is set to grow rapidly. Catalyst coated membranes (CCMs) are the key functional components of both fuel cells and electrolyzers. Such CCMs generally comprise a conductive polymer membrane coated on both sides with a catalyst-containing layer. CCMs are configured to drive oxidation and reduction reactions and support proton and electron transport; these processes are required for fuel cell and electrolyzer technologies to function.

[0003] While there are variations in the materials and composition of CCM components according to the functional performance requirements of the end application, they generally contain several useful components, including one or more platinum group metal (PGM) catalysts and one or more proton conducting polymers.

[0004] Typically, the membrane is formed from one or more ionomers, such as perfluorosulfonic acid (PFSA) ionomers. An ionomer may also be provided in one or both of the catalyst layers. The ionomer in the catalyst layer may be the same or different from the ionomer in the main membrane component and / or other catalyst layers.

[0005] The CCM can contain two different catalysts, one to drive the oxidation reaction on one side of the CCM and one to drive the reduction reaction on the other side of the CCM. The CCM may also contain a recombination catalyst provided to catalyze the recombination of hydrogen and oxygen to form water, reducing the amount of hydrogen that passes through the membrane and mixes with oxygen to form a potentially explosive mixture. The CCM may also contain a peroxide scavenger, e.g., a multivalent cation delivered as a salt or oxide (supported or unsupported) as a metal oxide such as CeO2.

[0006] CCM catalysts can be based on platinum group metals, such as platinum, ruthenium, iridium, palladium, or mixtures thereof. The platinum group metals may be provided in elemental (metal) form, compound form (e.g., oxides such as iridium oxide catalysts), or PGM-based metal alloys (e.g., PtCo). Additionally, PGM catalyst materials may be supported on substrate materials such as carbonaceous substrate materials (e.g., carbon, such as platinum-on-carbon catalysts comprising particles of platinum disposed on carbon or PtCo-on-carbon), or organic materials, such as the nanostructured thin film catalyst (NTFC) technology described in U.S. Patent No. 2020 / 102659 and WO 2006 / 089180).

[0007] Catalyst coated membranes (CCMs) can also be provided in combination with additional functional layers to form multilayer membrane electrode assemblies (MEAs). Such MEAs may have, for example, 3, 5, or 7 layers.

[0008] With the increase in CCM production for fuel cells and electrolyzers, there is also an associated increase in CCM waste material, including large amounts of scrap material generated during CCM production (e.g., due to failures in quality control), and an increase in end-of-life (EoL) CCM. Because CCMs contain several rare and / or valuable components, including platinum group metals (especially Pt, Pd, Ir, and Ru) and ionomers (in both membranes and catalyst layers), there is an increasing demand for methods to recycle such components from waste CCM material.

[0009] One current method for recovering PGMs from production scrap and end-of-life CCM materials involves incineration. The incineration process produces a PGM-rich (typically Pt and Ir) ash that is processed through conventional PGM purification routes. However, the incineration process releases harmful and toxic gases, such as CO and HF, from the polymers that are part of the membrane. Both of these gases have adverse effects because they pollute the atmosphere, increase the greenhouse effect, and / or have harmful effects on the human body. Therefore, a cleaner process is needed that reduces or eliminates the release of these gases.

[0010] In addition to the above, incineration methods destroy the ionomer components, which also have significant value. Therefore, it is desirable to provide a process that can recover both PGM and ionomer components, and also to provide a cleaner, safer, and more environmentally friendly process. Processes for recovering perfluorosulfonic acid ionomers are known. See, for example, WO 2016 / 156815 and U.S. Pat. No. 7,255,798. Furthermore, processes for recovering individual PGM catalyst components are known. See, for example, U.S. Pat. No. 7,709,135. Several other prior art documents that disclose methods for recycling components of CCM are discussed below.

[0011] EP 3275036 discloses a method that includes immersing a CCM in a diol solvent, heating to obtain a dispersion containing the solvent, one or more ionomers, and one or more catalyst components, and filtering the dispersion to separate the solvent and one or more ionomers from the one or more catalyst components.

[0012] A paper titled "PEM Water Electrolysis: Innovative Approaches Toward Catalyst Separation, Recovery, and Recycling" (International Journal of Hydrogen Energy 44 (2019) 3450-3455) discloses a method for recycling CCM to recover membrane ionomer, iridium oxide catalyst, and Pt / C catalyst. This is achieved by mounting the CCM across a reactor to define two separate chambers (one on the iridium oxide side of the CCM and one on the Pt / C side of the CCM). Each side of the CCM is then subjected to separate circulation of a solution consisting of deionized water and alcohol. Complete delamination of the catalyst layer from the membrane is reported to occur after 10 to 30 minutes. After delamination, the membrane is dried and can be reused or reprocessed. The two separate dispersions containing the catalyst residue are centrifuged, and the solids are collected and dried in an oven to yield recycled iridium oxide catalyst powder and recycled Pt / C catalyst powder. The recycled catalyst powder is used to produce new CCMs. It has been shown that the temperatures used to dry the recycled catalyst are not high enough to combust the ionomer in the catalyst powder, and that the ionomer present when the catalyst powder is reused in a new ink formulation may be responsible for the increased cell voltage (reduced performance) in CCMs produced using recycled catalyst material.

[0013] CN106898790 also discloses a method in which the catalyst layer is delaminated from the membrane using an alcohol-water mixture, and then the solid membrane is separated from the catalyst layer dispersion. The catalyst layer dispersion and the solid membrane are then processed and recycled separately. In contrast to the previously discussed paper, the catalyst layer dispersion is described as being processed by heating to a temperature sufficient to combust the catalyst layer ionomer, and then further heated at a higher temperature to remove the carbon and recover the precious metal catalyst.

[0014] To enable fuel cells and electrolyzers to become more sustainable technologies, there remains a need for commercially viable and environmentally friendly routes to recover, separate, and recycle both PGM and ionomer components from waste CCM materials, including production scrap and end-of-life materials. The purpose of this document is to address this issue. Summary of the Invention

[0015] As noted in the Background section, a catalyst coated membrane (CCM) can comprise an ionomer membrane coated on either side with a catalyst layer containing both ionomer and catalytic material. One prior art method for recycling the ionomer in the membrane and catalytic material involves dispersing the ionomer membrane to form a slurry containing the ionomer and catalytic material, separating the catalytic material from the ionomer material, and then processing the ionomer and catalytic material separately.

[0016] However, typically, more than 80% of the recycled ionomer is present in the membrane and more than 80% of the catalytic material is present in the catalyst layers. A process for delaminating the catalyst layers to separate them from the ionomer membrane allows the bulk of the ionomer to be processed and recovered separately from the bulk of the catalytic material.

[0017] One prior art method for delaminating catalyst layers from membranes without dispersing them is described in a paper titled "PEM Water Electrolysis: Innovative Approaches Toward Catalyst Separation, Recovery, and Recycling," which is discussed in the Background section. However, that method results in recovered catalyst material that is contaminated with ionomer from the original catalyst layer, which reduces the performance of the catalyst material when reused in forming new CCMs. A solution to this problem is described in Chinese Patent No. 106898790, which is also discussed in the Background section. That document proposes delaminating the catalyst layer and then processing the catalyst layer material to combust the catalyst layer ionomer and carbon material and recover the ionomer-free precious metal catalyst from the delaminated catalyst layer.

[0018] However, the present inventors have recognized that this approach is problematic. Burning catalyst-layered ionomers releases harmful and toxic gases, such as CO and HF, from the catalyst-layered ionomers. Both of these gases have adverse effects because they pollute the atmosphere, increase the greenhouse effect, and / or have harmful effects on the human body. Therefore, a cleaner process is needed that reduces or eliminates the release of these gases.

[0019] Furthermore, the incineration process destroys the valuable catalyst layer ionomer components. Therefore, it would be desirable to provide a process that can recover the PGM catalyst material, the bulk membrane ionomer, and also the ionomer from the catalyst layer, as well as to provide a cleaner, safer, and more environmentally friendly process.

[0020] According to the present specification, there is provided a method for recycling spent catalyst coated membranes, the spent catalyst coated membranes comprising a membrane comprising a membrane ionomer, a first catalyst layer disposed on one side of the membrane, the first catalyst layer comprising a first catalyst and a first catalyst layer ionomer, and a second catalyst layer disposed on an opposite side of the membrane, the second catalyst layer comprising a second catalyst and a second catalyst layer ionomer, the method comprising: contacting the spent catalyst coated membrane with a solvent to delaminate both the first and second catalyst layers from the membrane without dispersing the membrane, wherein the first and second catalyst layers form a catalyst layer slurry comprising the first catalyst, the first catalyst layer ionomer, the second catalyst, and the second catalyst layer ionomer; Separating the membrane from the catalyst layer slurry; treating the membrane to recover the membrane ionomer; treating the catalyst layer slurry to disperse and recover the first and second catalyst layer ionomers in a solvent, and separating and recovering the first and second catalysts or components thereof.

[0021] The catalyst layer slurry is treated by: heating the catalyst layer slurry to disperse the first and second catalyst layer ionomers and form an ionomer dispersion having the solid first and second catalyst materials disposed therein; separating the solid first and second catalyst materials from the ionomer dispersion (e.g., using a solid-liquid separation technique such as filtration); treating the ionomer dispersion to recover first and second catalyst layer ionomers; and treating the solid first and second catalytic materials to separate and recover the first and second catalytic materials or components thereof.

[0022] The step of heating the catalyst layer slurry to disperse the first and second catalyst layer ionomers can be performed in the same solvent used to delaminate the first and second catalyst layers from the membrane. Alternatively, the catalyst slurry can be treated to remove the solvent used in the delamination process, and the material can then be reslurried in a different solvent to disperse and separate the catalyst layer ionomers. One or more of the catalyst layer components can be leached either before and / or after the material is reslurried to disperse the catalyst layer ionomer material.

[0023] An important feature of this methodology is that it is adapted to recover catalyst layer ionomer in addition to the bulk membrane ionomer and catalyst material. After delaminating the catalyst layer from the membrane to form the catalyst layer slurry, the catalyst layer slurry is processed to form a dispersion of catalyst layer ionomer in a solvent so that the ionomer dispersion can be separated from the solid catalyst components. This allows the catalyst layer ionomer to be recovered separately from the catalyst material and bulk membrane ionomer. Thus, the process reduces or eliminates ionomer contamination in the recovered catalyst material, avoids ionomer combustion processes that release harmful and toxic gases, and allows the catalyst layer ionomer to be recycled and reused.

[0024] Additionally, the solvents used in the recycling process can be treated with ion exchange, activated carbon, or other active media to reduce the levels of low molecular weight ionic / soluble compounds. This allows for recycling of the solvent and reduces waste. The low molecular weight contaminants can then be incinerated or otherwise disposed of. [Brief explanation of the drawings]

[0025] For a better understanding of the invention and to show how the same may be carried into effect, specific embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0026] [Figure 1]A waste CCM recycling process is shown in which the catalyst layer is first separated from the bulk polymer membrane (note that the gas diffusion layers and seals can be removed before processing the waste CCM). [Figure 2] Methods for further processing the catalyst layer material are presented. [Figure 3] Another method for further processing the catalyst layer material is shown. [Figure 4] (a) Catalyst coated membrane subjected to size reduction (cutting) and soaking in an alcohol:water mixture (left image), (b) after ultrasonic treatment where the catalyst layer was dispersed in the alcohol:water mixture (center image), and (c) a clean, transparent exfoliated membrane recovered from the alcohol:water mixture (right image). [Figure 5] Images of post-treatment dispersions of catalyst coated membranes in a range of different alcohol:water mixtures and recovered membranes are shown, showing that methanol is ineffective at delaminating the catalyst layer from the membrane (image a), while the order of effectiveness of other alcohols in achieving delamination of the catalyst layer and recovery of clean, transparent membranes is as follows: n-butanol > n-propanol > i-propanol > ethanol (image b). [Figure 6] An example of a process flow for treating waste dispersion medium in a CCM recycling process is shown below. DETAILED DESCRIPTION OF THE INVENTION

[0027] A CCM may contain ionomers in one or both of the catalyst layers, as well as in the bulk ionomer membrane in which the catalyst layers are disposed. Different ionomers can be used in the catalyst layers and the bulk ionomer membrane to optimize the performance parameters of the CCM. This specification relates to methods in which the catalyst layer ionomer can be separated from the membrane ionomer and processed such that the membrane and catalyst layer ionomer are both recovered in addition to the PGM-containing catalyst material.

[0028] As described in the Abstract section, the present specification provides a method for recycling spent catalyst coated membranes, the spent catalyst coated membranes comprising a membrane comprising a membrane ionomer, a first catalyst layer disposed on one side of the membrane, the first catalyst layer comprising a first catalyst and a first catalyst layer ionomer, and a second catalyst layer disposed on an opposite side of the membrane, the second catalyst layer comprising a second catalyst and a second catalyst layer ionomer, the method comprising: contacting the spent catalyst coated membrane with a solvent to delaminate both the first and second catalyst layers from the membrane without dispersing the membrane, wherein the first and second catalyst layers form a catalyst layer slurry comprising the first catalyst, the first catalyst layer ionomer, the second catalyst, and the second catalyst layer ionomer; Separating the membrane from the catalyst layer slurry; treating the membrane to recover the membrane ionomer; treating the catalyst layer slurry to disperse and recover the first and second catalyst layer ionomers in a solvent, and separating and recovering the first and second catalysts or components thereof.

[0029] The catalyst layer slurry is treated by: heating the catalyst layer slurry to disperse the first and second catalyst layer ionomers and form an ionomer dispersion having the solid first and second catalyst materials disposed therein; separating the solid first and second catalyst materials from the ionomer dispersion (e.g., using a solid-liquid separation technique such as filtration); treating the ionomer dispersion to recover first and second catalyst layer ionomers; and treating the solid first and second catalytic materials to separate and recover the first and second catalytic materials or components thereof.

[0030] The step of heating the catalyst layer slurry to disperse the first and second catalyst layer ionomers can be performed in the same solvent used to delaminate the first and second catalyst layers from the membrane. Alternatively, the catalyst slurry can be treated to adjust the solvent composition or remove the solvent used in the delamination process, and the material can then be reslurried in a different solvent to thereby disperse and isolate the catalyst layer ionomers. One or more of the catalyst layer components can be leached either before and / or after the material is reslurried to disperse the catalyst layer ionomer material.

[0031] Typically, the step of heating the catalyst layer slurry to disperse the first and second catalyst layer ionomers is performed at a higher temperature than the step of contacting the spent catalyst-coated membrane with a solvent to delaminate both the first and second catalyst layers from the membrane without dispersing the membrane. This is particularly true when the solvent used to delaminate the catalyst layers from the membrane is the same. In the delamination process, the temperature is kept low enough so that the membrane ionomer does not disperse, but the catalyst layers delaminate to form a slurry. Then, after separating the membrane from the slurry, the temperature of the slurry can be increased to disperse the catalyst layer ionomers and separate them from the solid catalyst material. The step of heating the catalyst layer slurry to disperse the first and second catalyst layer ionomers in the solvent can also be performed at high pressure in an autoclave.

[0032] The treatment of the catalyst layer slurry may further include converting the first and second catalyst layer ionomers to a salt form. Salt formation (e.g., by treatment with a base) protects the sulfonic acid groups of the ionomers during the recovery process, and the salt forms of the first and second catalyst layer ionomers can then be converted back to the acid form by proton exchange. The catalyst layer ionomer dispersion is also advantageously subjected to ion exchange to remove metal contaminants.

[0033] The first and second catalyst layer ionomers can be recovered from the ionomer dispersion as a blend of the first and second catalyst layer ionomers, or alternatively, the ionomer dispersion can be processed to separate the first and second catalyst layer ionomers.

[0034] In catalyst-coated membranes with different ionomers in the catalyst layer compared to bulk ionomer membranes, the process of delaminating the catalyst layer can be used to separate the different types of ionomers in the membrane and catalyst layer so that they can be processed separately. In this regard, it is noted that in prior art methods involving dispersing both the catalyst layer ionomer and the bulk membrane ionomer, it can be difficult to separate the mixed ionomer dispersion when the ionomer in the catalyst layer is different from the ionomer in the bulk membrane, especially since a large amount of ionomer from the membrane is present. In the present methodology, in which the catalyst layer is first delaminated and separated from the bulk membrane, the catalyst layer ionomer dispersion is processed separately from the majority of the CCM ionomer remaining in the membrane. The different types of ionomers can be separated more easily, and the smaller volume of ionomer from the catalyst layer alone is easier to process, for example, to remove metal contamination and / or separate the different types of ionomer.

[0035] The solvent used to delaminate both the first and second catalyst layers from the membrane can be a mixture of alcohol and water, where the alcohol in the mixture is selected from n-butanol, n-propanol, i-propanol, or ethanol. While methanol and water are not effective at delaminating catalyst layers from ionomer membranes, it has been found that mixtures of n-butanol, n-propanol, i-propanol, or ethanol with water can effectively delaminate catalyst layers and disperse the catalyst layer ionomer without dispersing the bulk ionomer membrane. The order of effectiveness of these alcohols in achieving delamination of the catalyst layer and recovery of a clean, transparent membrane is as follows: n-butanol > n-propanol > i-propanol > ethanol. Therefore, the alcohol is preferably selected from n-butanol, n-propanol, or i-propanol, more preferably n-butanol or n-propanol, and most preferably n-butanol. The selection can be based on the appropriate Hansen Solubility Parameter range.

[0036] The alcohol and water mixture may have a volume ratio of alcohol:water between 0 and 1, which is advantageously at least 50:50, 60:40, or 70:30; up to 95:5, 90:10, or 85:15, or within a range defined by any combination of the aforementioned lower and upper limits. The ratio can be optimized to enable effective delamination of the catalyst layer to form a catalyst layer slurry without dispersing the bulk ionomer membrane for a given set of process conditions and CCM feed material for recycle.

[0037] The solvent (e.g., a mixture of alcohol and water) can be agitated, for example, by sonication, to aid in delamination of the catalyst layer. Sonication has been found to be effective for use in the present method. Furthermore, during the step of contacting the membrane with the solvent to delaminate the catalyst layer, the solvent can be maintained at a temperature less than 150°C, 100°C, 80°C, 60°C, or 40°C, optionally greater than 5°C, 10°C, or 15°C, optionally within a range defined by any of the aforementioned upper and lower limits. The temperature can be sufficiently low so that the catalyst layer delaminates without dispersing the fluorinated polymer membrane, which remains in a solid, undispersed form.

[0038] Contacting the spent catalyst coated membrane with the solvent to delaminate the catalyst layer can be carried out for a time period of at least 10 minutes, 20 minutes, 30 minutes, or 1 hour; up to 5 hours, 3 hours, or 2 hours, or within a range defined by any combination of the aforementioned lower and upper limits. The specific time period for the delamination step will depend on a given set of process conditions (e.g., alcohol type / concentration, temperature, pressure, agitation, etc.) and the type of CCM feed material for recycle.

[0039] Advantageously, the spent catalyst coated membrane is processed (e.g., by cutting) into pieces before contacting it with a solvent to delaminate the catalyst layers. This can aid in the clean delamination of the catalyst layers from the bulk ionomer membrane and can make it easier to handle and process large areas of spent catalyst coated membrane material (e.g., amounts ranging from 5% to 100% of the original membrane).

[0040] Typically, the first catalyst may include platinum, palladium, and / or ruthenium (optionally on a support material such as a carbon support material), and the second catalyst may include iridium (e.g., an iridium oxide material). The methodology is particularly suitable for recycling catalyst-coated membranes in which the membrane ionomer is different from one or both of the first and second catalyst layer ionomers. The catalyst layer ionomers may be the same or different from one another.

[0041] After delaminating the catalyst layer to yield a solid bulk ionomer membrane in the catalyst layer slurry, the solid bulk ionomer membrane can be separated from the slurry using solid-liquid separation techniques such as dispensing and / or filtration. The solid bulk ionomer membrane can then be further processed to recover the membrane ionomer without interference from the catalyst layer ionomer. Further processing of the bulk ionomer membrane can include dispersing the membrane ionomer in a solvent and separating the dispersed membrane ionomer from other components of the bulk ionomer membrane, such as the reinforcing polymer. The recovered membrane ionomer can then be reused to manufacture new membrane materials.

[0042] The catalyst layer slurry can be processed separately to recover the first and second catalyst layer ionomers and the first and second catalyst materials. For example, the first and second catalysts can be filtered from the catalyst layer ionomer dispersion and then subjected to a selective dissolution and purification step to recover the individual platinum group metals. Processing of the catalyst layer slurry can also include grinding the catalyst layer material prior to the selective dissolution and purification step to recover the individual platinum group metals. The remaining catalyst layer ionomer dispersion can be recycled to produce new catalyst layer inks.

[0043] An example process flow is shown in Figure 1. The first stage of this process involves separating the catalyst layer from the membrane. The CCM material can be immersed in an alcohol-water mixture and sonicated or otherwise agitated for a period of time during which the catalyst layer separates and disperses in the solvent. Once the membrane and catalyst layer are cleanly separated, the membrane can be further processed to recover the membrane ionomer components. To recover the PGM and ionomer in the catalyst layer, there are two options, A and B, as shown in Figures 2 and 3.

[0044] Process Option A: The catalyst layer material can be subjected to an HCl / oxidant (e.g., chlorine) treatment to leach platinum. The liquid from this treatment can then be purified from base metals (e.g., using a cation exchange resin), undergo Ru removal via distillation or other processes, and then directly enter the Pt purification stream. The remaining Ir-containing residue from leaching can undergo a process involving heating / autoclaving the material in an alcohol solvent to dissolve / disperse the ionomer. The ionomer dispersion is separated from the Ir-containing solution by filtration or centrifugation (alternatively, the Ir can be leached before or after the ionomer dispersion). The ionomer dispersion can then proceed to further processing and be recycled back to produce new CCM. The Ir-containing residue can be processed for direct reuse of the Ir catalyst, or the residue can be purified to recover the Ir metal.

[0045] Process Option B: Alternatively, the catalyst layer material can be heated to high temperatures in a solvent (e.g., an alcohol solvent) and optionally autoclaved to disperse the catalyst layer components. The resulting slurry then undergoes solid / liquid separation by either filtration or centrifugation. The supernatant / filtrate contains the dispersed ionomer, which can then be further processed and recycled back to produce new CCM. The PGM residue is dried to ensure complete removal of the (organic) solvent before being subjected to the HCl / chlorine leaching process. The liquor from this leaching process can then be purified from base metals (e.g., using a cation exchange resin), undergo Ru removal via a distillation process, and then enter the Pt purification stream directly. The residue from the leaching process still contains the Ir catalyst, which is largely unchanged due to its stability. It can be processed for direct reuse of the Ir catalyst, or the residue can be purified to recover the Ir metal.

[0046] A common feature of the catalyst layer recycling processes described above is the use of oxidative acid leaching to extract platinum (and / or palladium and / or ruthenium) materials, followed by extraction of the platinum and ionomer dispersion followed by extraction of iridium via either reductive acid leaching or solid-liquid separation. Pt leaching can be applied before or after dispersing the ionomer, and before or after iridium leaching. The process sequence can be (i) iridium leaching, (ii) platinum leaching, and (iii) treatment of the remaining catalyst layer ionomer. Alternatively, the process sequence can be (i) platinum leaching, (ii) iridium leaching, and (iii) treatment of the remaining catalyst layer ionomer. Alternatively, iridium leaching is not required to separate the iridium from the ionomer. Rather, the iridium-containing material is separated from the catalyst layer ionomer material by dispersing the ionomer material and removing the ionomer using solid / solution separation. In this case, solid / liquid separation can be used to separate insoluble Ir-, Pt-, Ru-, and / or Rh-containing species / alloys. The platinum leaching step can be performed before the ionomer dispersion step, as in Figure 2. Alternatively, the ionomer dispersion step can be performed before the platinum leaching step, as in Figure 3. In either case, the process first separates the catalyst layer from the bulk polymer membrane, and then applies treatment steps to the catalyst layer material with the bulk ionomer membrane being treated separately.

[0047] The particular method utilized will depend on the operator's needs, the demand for the components, and the desired form of the material recovered by the process. For example, if it is desirable to extract a component early in the recycle process, e.g., due to a shortage of that particular component, an appropriate process flow can be selected to obtain the desired component early in the process rather than holding a significant amount of the component for an extended period of time within the recycle process. For example, if it is desirable to recover the bulk of the ionomer early in the process, the process herein can be selected because the initial step of removing the catalyst layer from the bulk ionomer membrane ensures that the bulk ionomer membrane can be quickly recovered and processed, while the ionomer and PGM in the catalyst layer are available for further processing to perform various separation steps.

[0048] Methods for recovering ionomers are described in U.S. Pat. No. 7,255,798 and WO 2016 / 156815, and such methods can be incorporated into the process flow herein as described above. As discussed above, often a different ionomer can be used in one or both of the catalyst layers compared to the ionomer in the bulk membrane. The different ionomers can be selected to provide improved performance in the end application. It is also possible to use a blend of ionomers or to have layers of different ionomers within the bulk polymer membrane. In such cases, the process flow herein can be useful for separating the bulk polymer membrane from the catalyst layer at the start of the process flow. If a different ionomer is used in the catalyst layer compared to the bulk membrane, such separation can be useful for separating the different ionomers before further processing.

[0049] Catalyst layer delamination process The spent catalyst coated membrane can be contacted and agitated with a mixture of alcohol and water to delaminate both the first and second catalyst layers from the membrane without dispersing the membrane, and the first and second catalyst layers are dispersed in the mixture of alcohol and water to form a catalyst layer dispersion comprising the first catalyst, the first catalyst layer ionomer, the second catalyst, and the second catalyst layer ionomer.

[0050] Figure 4 shows (a) a catalyst-coated membrane subjected to size reduction (cutting) and soaking in an 80:20 alcohol:water mixture (left image), (b) after ultrasonic treatment where the catalyst layer was dispersed in the solution (center image), and (c) a clean, transparent delaminated membrane recovered from the alcohol:water mixture (right image).

[0051] The alcohol in the alcohol and water mixture is selected from n-butanol, n-propanol, i-propanol, or ethanol. While methanol and water are not effective at delaminating the catalyst layer from the ionomer membrane, it has been found that a mixture of n-butanol, n-propanol, i-propanol, or ethanol with water can effectively delaminate the catalyst layer and disperse the catalyst layer ionomer without dispersing the bulk ionomer membrane. The order of effectiveness of these alcohols in achieving delamination of the catalyst layer and recovery of a clean, transparent membrane is as follows: n-butanol > n-propanol > i-propanol > ethanol. Therefore, the alcohol is preferably selected from n-butanol, n-propanol, or i-propanol, more preferably n-butanol or n-propanol, and most preferably n-butanol. FIG. 5 shows images of the dispersions and recovered membranes after treatment of catalyst-coated membranes in a range of different alcohol:water mixtures, demonstrating that methanol was ineffective at delaminating the catalyst layer from the membrane (image a), while the order of effectiveness of the other alcohols in achieving delamination of the catalyst layer and recovery of clean, transparent membranes was as follows: n-butanol > n-propanol > i-propanol > ethanol (image b).

[0052] The alcohol and water mixture may have a volume ratio of alcohol:water of 0 to 1, which is advantageously at least 50:50, 60:40, or 70:30; up to 95:5, 90:10, or 85:15, or within a range defined by any combination of the aforementioned lower and upper limits. The ratio can be optimized to allow effective dispersion of the catalyst layer ionomer without dispersing the bulk ionomer membrane for a given set of process conditions and CCM feed materials for recycle.

[0053] The alcohol and water mixture can be agitated by ultrasonic treatment. Ultrasonic treatment has been found to be effective for use in the present method. Contacting the spent catalyst-coated membrane with the alcohol and water mixture to delaminate the catalyst layer can be carried out for a time period of at least 10 minutes, 20 minutes, 30 minutes, or 1 hour; up to 5 hours, 3 hours, or 2 hours, or within a range defined by any combination of the aforementioned lower and upper limits. The specific time period for the delamination step depends on a given set of process conditions (such as alcohol type / concentration, temperature, pressure, agitation, etc.) and the type of CCM feed material for recycling.

[0054] Advantageously, the spent catalyst coated membrane is processed (e.g., by cutting) into pieces before contacting it with the alcohol and water mixture, which can aid in clean delamination of the catalyst layers from the bulk ionomer membrane and can make handling and processing of large areas of spent catalyst coated membrane material easier.

[0055] In relation to the above, it should be noted that certain prior art methods for recycling CCMs use pure ethylene glycol and heat, and the CCM receives a complete dispersion containing the ionomer in the bulk membrane and catalyst layer. Certain prior art methods also refer to the use of alcohol / water mixtures, generally for recycling catalyst materials. The difference here is that a solvent system, such as an alcohol / water system, is used and conditions are adjusted to selectively separate and recycle the different ionomers in the bulk membrane and catalyst layer.

[0056] Further processing to recover ionomer from catalyst layer material The processing steps for recovering the ionomer from the catalyst layer material may include: Optionally convert the ionomer to a salt form Heating to disperse the ionomer ○ High enough temperature for dispersion, optionally in an autoclave Separation of catalyst and catalyst support from ionomer dispersion using: ■ Centrifugation, and / or ■ Filtration, e.g. Ultrafiltration Membrane filtration, and / or Cross-flow filtration Ion exchange to remove metal contaminants Optionally convert back to the acid form

[0057] Further processing to recover the ionomer from the membrane The processing steps for recovering the ionomer from the bulk membrane may include: Optionally converting the ionomer to a salt form (e.g., before dispersing the membrane ionomer) Dispersion in water (hydrothermal process using an autoclave), aqueous solutions, aqueous alkali solutions, organic solvents (e.g. alcohols, diols, phosphates, ketones, DMSO, DMF, NMP), or mixtures thereof.

[0058] Filter particles Ion exchange to remove metal contaminants Optionally convert back to the acid form Optionally, treat the waste solvent by ion exchange or by contacting it with an activated medium such as activated carbon / charcoal.

[0059] Further Processing of the Ionomer The ionomer recovered from the bulk membrane and / or catalyst layer according to the aforementioned process can be further purified by subjecting it to an ultrafiltration process and subjected to a separation and / or blending process.

[0060] Catalyst layer material processing process The catalyst layer material separated from the bulk polymer membrane using the aforementioned process will generally contain an ionomer, at least one catalyst containing platinum, palladium, and / or ruthenium, and at least one catalyst containing iridium. This material can be processed to recover the PGMs and ionomer using the following general method: (a) treating the material with a heated solution containing an acid and an oxidizing agent, wherein platinum, palladium, and / or ruthenium are leached from the material into solution, and the solution is separated from the remaining solid components of the material; (b) treating the material with a solvent to disperse the ionomer and recovering the ionomer dispersion, wherein the ionomer dispersion occurs before or after leaching of the platinum, palladium, and / or ruthenium; and (c) Below: (i) separating the remaining solid iridium-containing catalyst material from the ionomer dispersion after leaching of platinum, palladium, rhodium, and / or ruthenium and dispersion of the ionomer; (ii) treating the material to extract iridium by one or both of: leaching iridium from the material using a heated solution containing an acid and a reducing agent, and separating the leached iridium-containing solution from the remaining solid components of the material, where iridium leaching occurs before or after leaching of platinum, palladium, and / or ruthenium.

[0061] The steps of the process can be performed in any order to recover Pt, Ir, and the ionomer: Pt-Ir-ionomer, Ir-Pt-ionomer, ionomer-Pt-Ir, ionomer-Ir-Pt, Pt-ionomer-Ir, or Ir-ionomer-Pt.

[0062] The following description focuses on examples involving a platinum catalyst and an iridium-based catalyst (e.g., IrOx), however, the same approach can be used when the platinum catalyst is replaced with a palladium catalyst, a ruthenium catalyst, a mixed PGM catalyst including a combination of at least two of platinum, palladium, and ruthenium, or a catalyst including at least one PGM and at least one non-PGM metal (e.g., PtCo).

[0063] The acid used in one or both of the iridium and platinum leaching is optionally hydrochloric acid. Furthermore, one or both of the solutions used in the platinum and iridium leaching is preferably heated to a temperature of at least 50°C, 60°C, or 70°C; or up to 160°C, 100°C, or 90°C, or within a range defined by any combination of the aforementioned lower and upper limits; if the solution is heated above 100°C, this is done in a pressurized vessel. The oxidizing agent for platinum leaching can include, for example, a chlorate salt, such as sodium chlorate solution or chlorine gas (e.g., generated in situ electrolytically). The oxidizing agent can be added to the hydrochloric acid solution after heating to the above temperatures. The solution can include concentrated HCl, for example, about 6M HCl.

[0064] Separation of the solution containing the leached platinum can be accomplished by filtration. The separated solution may be concentrated by boiling the solution to an appropriate PGM concentration for further processing. Alternatively, the leachate can be recycled to leach platinum from additional spent catalyst coated membrane material, and the recycle is repeated as necessary until the target PGM concentration is reached. The PGM-containing leachate is then further processed to extract platinum from the acidic solution using known techniques. The remaining solid components of the spent catalyst layer material can be processed separately.

[0065] The method further includes extracting iridium from the spent catalyst layer material. This can be accomplished by leaching Ir species from the spent catalyst layer material via a reductive dissolution process using an acid (e.g., 8-12 M HCl) and a reducing agent (e.g., hydrazine, NaBH4, or ammonium oxalate) to obtain an Ir-containing acidic solution. WO 2021 / 083758 describes several examples of such processes for dissolving Ir in a reducing HCl environment. Because the aforementioned oxidative acidic platinum leach does not leach iridium to a significant extent, such a reductive acidic leach process step for iridium can be performed after the oxidative acidic leach step for platinum. However, it is also contemplated that iridium leaching can be performed before platinum leaching. Thus, the proposed route according to this example is a two-step process involving selective leaching of Ir and Pt species from spent CCM without the need for incineration or other destructive treatment. The steps are as follows, and can be performed in any order: 1. Leaching of Ir species via a reductive dissolution process using an acid (such as HCl or nitric acid) and a reducing agent (such as hydrazine) results in an Ir-containing acidic solution and an undissolved residue. 2. Leaching of Pt species via an oxidative dissolution process using an acid (such as HCl) and an oxidizing agent (such as chlorate or Cl2) results in a Pt-containing acidic solution and an undissolved residue.

[0066] The liquids produced from steps 1 and 2 can then be directed to their respective purification processes (if significant impurities are present) or can be used directly as precursors for new catalyst materials. The solid residue can then be further leached to remove any remaining PGM species, and the resulting ionomer residue can then be recycled.

[0067] This process selectively recovers PGMs from spent catalyst bed material and allows for a simple, further recovery process for the remaining catalyst bed ionomer. Therefore, the process offers a complete recovery and recycling route for both PGMs and ionomers. The two-step process, including Pt and Ir leaching, allows for a simple and rapid route to separate and recover both Ir and Pt, with the potential to feed the metal solution directly back into the catalyst manufacturing process. With an estimated need for approximately 800 kOzt Pt and 160 kOzt Ir for fuel cell and electrolyzer CCMs by 2040, the compact, custom-built nature of the process shortens lead times and increases metal flowability. This process allows for the generation of a closed-loop cycle for scrap CCM material, not only PGMs but also ionomers. This process also allows for open-loop recycling of end-of-life CCMs.

[0068] Instead of leaching iridium as described above, iridium (or iridium oxide) material can be separated from the catalyst layer by dispersing an ionomer. In this case, platinum can be leached from the spent catalyst layer material as described above, and the remaining spent catalyst layer material containing the solid ionomer and iridium species can then be subjected to an ionomer dispersion to obtain a slurry containing the ionomer dispersion in which the solid iridium species are disposed. The ionomer dispersion can be separated from the solid iridium species using solid / liquid separation (e.g., filtration or centrifugation) to obtain the ionomer dispersion for recycling. The remaining solid iridium material can be directly reused in the CCM production process or purified before reuse. Alternatively, the catalyst layer ionomer can be dispersed prior to platinum leaching to obtain a mixed PGM residue for further processing.

[0069] In one such example, spent catalyst bed material is subjected to an HCl / oxidant (e.g., chlorine) treatment to leach platinum, and optionally ruthenium, if present in the spent catalyst bed material. The liquor from this treatment can then be treated to remove base metals such as nickel and cobalt (e.g., using a cation exchange resin), followed by Ru removal via distillation or other processes, and then directly into a Pt purification process stream to recover Pt. The residual spent catalyst bed material from the leaching can undergo a process involving heating / autoclaving the material in a solvent (e.g., an alcohol solvent) to disperse the ionomer. The ionomer dispersion can then be separated from the Ir-containing solids by filtration or centrifugation. The ionomer dispersion can then proceed to further processing or be recycled back to produce new CCMs, either as pure or blended materials. Examples of processes for recycling perfluorosulfonic acid ionomers are described in U.S. Pat. No. 7,255,798 and WO 2016 / 156815. Due to its inherent stability, the Ir catalyst can be reused without further treatment, or the Ir solids can be purified to recover the Ir metal.

[0070] In the above process, the platinum leaching step is performed on the spent catalyst bed material before the ionomer dispersion step. However, in an alternative method, the ionomer dispersion is performed before the platinum leaching step. In this case, the spent catalyst bed material can be heated to high temperatures in a solvent (e.g., an alcohol solvent) and optionally autoclaved to disperse the ionomer. The resulting slurry is subjected to solid / liquid separation (e.g., by either filtration or centrifugation). The solution, containing the dispersed ionomer, is then further processed and recycled back to produce new CCM. The PGM residue may be dried to ensure complete removal of the organic solvent before undergoing the HCl / chlorine leaching process as described above. The liquor from the leaching can be treated to remove base metals such as Ni and / or Co (e.g., with a cation exchange resin) and Ru removal (e.g., via a distillation process), and the remaining platinum-containing solution can then be fed to a Pt purification process stream to recover Pt as described above. The residue from the leaching process still contains the Ir catalyst, which remains largely unchanged due to its stability. This can be processed to directly reuse the Ir catalyst material (eg, IrOx) or the residue can be purified to recover the Ir.

[0071] Disposal of waste dispersion medium After treating the membrane to recover the membrane ionomer and / or treating the catalyst layer slurry to disperse and recover the first and second catalyst layer ionomers, a waste dispersion medium is produced, containing solvent and fluorine-containing species such as soluble fluorine-containing organic compounds, soluble fluoride species, and / or insoluble fluorine-containing species such as insoluble metal fluorides. The waste dispersion medium can be treated to reduce the concentration of fluorine-containing species in the solvent, after which the solvent can be safely disposed of or recycled for reuse in processing additional membrane and / or catalyst layer slurry materials. Treatment of the waste dispersion medium may include contacting the waste dispersion medium with a solid adsorbent and / or ion exchange medium to reduce the concentration of fluorine-containing species in the solvent and, optionally, to reduce the concentration of residual metal cations in the solvent. The waste dispersion medium may also be subjected to cross-flow filtration or ultrafiltration, for example, before contacting the waste dispersion medium with an adsorbent such as activated carbon and / or before contacting the waste dispersion medium with one or more ion exchange media.

[0072] In light of the above, this specification also provides a treatment method for a dispersing medium (e.g., water, aqueous alkaline solution, or water / alcohol mixture) used in recycling ionomer from CCM membrane components and / or catalyst layer components. The used dispersing medium can be contacted with a capture medium such as a cationic ion exchange resin and, optionally, an anionic ion exchange resin and / or activated carbon. The resulting treated used dispersing medium has reduced levels of low molecular weight soluble organic compounds, such as fluorinated or partially fluorinated sulfonic or carboxylic acids, and (optionally) reduced levels of residual cations, such as iron, nickel, copper, and chromium. The treated dispersing medium can then be reused in a closed-loop system or safely disposed of. Optionally, the used dispersing medium can first be subjected to a cross-flow filtration or ultrafiltration step to concentrate impurities before trapping and disposing of the fluorine-containing impurities. The ion exchange resin can be regenerated. The waste stream can be concentrated and disposed of by thermal decomposition (e.g., using a thermal oxidizer). The activated carbon column can also be thermally decomposed at the end of its life.

[0073] Figure 6 shows an example process flow for waste carrier fluid treatment. Advantages of this waste carrier fluid treatment method include reduced emissions resulting from the recycling of ionomer from production scrap and / or end-of-life fuel cell and / or water electrolyzer CCM components. Reduced water consumption is also advantageous.

[0074] Examples of solid media that can be used to extract fluorine-containing species from waste dispersion media include adsorbents such as carbon-based adsorbents, such as activated carbon, silica-based adsorbents, metal-based adsorbents, and / or ion-exchange resins that can adsorb / react with F. Ion-exchange resins include, for example, zirconium or aluminum preloaded chelating resins with amino-methylphosphonic acid functional groups, strong basic anion-exchange resins containing quaternary ammonium functional groups, and metal ion (e.g., Fe)-containing resins. 3+ , Al 3+ , Ce 3+ , and / or La 3+ Examples of suitable adsorbents include iminodiacetic acid-functionalized cation exchange resins preloaded with fluorine, or cryptand ligands. The adsorbent may be a silica-based adsorbent, e.g., a glass material such as a barium-silicate glass material, which may be provided in glass powder form. Fluorine-containing waste dispersion medium can be passed through a packed column or bed of such adsorbents to remove fluorine-containing species. The adsorbent can be periodically replaced and / or treated to remove fluorine and regenerate the adsorbent for reuse. overview

[0075] The present methodology combines operations to form a process for ionomer and PGM recovery from CCM, including delamination (and optionally comminution) of the catalyst layer from the bulk membrane, to produce a more concentrated ionomer-containing membrane stream and a more concentrated PGM-containing catalyst layer stream from which the PGMs can be more effectively leached, while also allowing for recovery of the catalyst layer ionomer.

[0076] Provided that the alcohol / water solvent system is present, by adjusting the conditions (type / concentration of alcohol, temperature, pressure, time, agitation), it is possible to process the CCM (or MEA) to achieve one or more of the following results: 1. Delamination of the catalyst layer only. 2. Delamination of the catalyst layer with dispersion of ionomer selective to the catalyst layer ionomer. 3. Delamination of the catalyst layers with complete dispersion of the ionomer in all three components (membrane, anode, and cathode catalyst layers).

[0077] The process may be preceded and / or followed by one or more of the following steps: 4. Leaching of PGMs from the catalyst bed. 5. Dispersion of ionomer from PGM leaching catalyst bed. 6. Dispersion of ionomer from the membrane.

[0078] Conditions can be adjusted to achieve the desired results. Of particular note here is the purpose of using an alcohol / water mixture. Previous work has focused on selective PGM separation and recycling, e.g., keeping anode PGM separate from cathode PGM. In contrast, here we confirm that specific alcohol / water mixtures can be used for ionomer / ionomer separation. Most ionomer recycling processes for CCMs focus on complete dispersion of all ionomers in the CCM, meaning that ionomer-to-ionomer separation must be addressed in a different way. It is likely that future CCMs will contain multiple ionomers. This method of delaminating catalyst layer ionomers from membranes provides an industrially viable approach for handling such multi-ionomer CCMs and potentially represents the best / only method for separating ionomers during scaled industrial CCM recycling processes when different ionomers are used in the catalyst layer and bulk membrane.

[0079] The drivers for PFSA recycling are generally as follows: 1. Legislation - Stricter regulation of PFA use due to their persistence in the environment. 2. Economics - The cost of ionomers can be comparable to the cost of precious metals in PEM products. 3. Environmental sustainability – Current routes to PGM recovery involve incineration, which releases high levels of toxic and corrosive HF and an associated CO2 footprint.

[0080] Establishing an industrially viable PFSA recycling process will enhance the attractiveness of hydrogen technology using CCMs and provide an opportunity for a circular, closed-loop recycling pathway for hydrogen technology products. More specifically, the present invention provides a methodology for mixed ionomer recycling that has flexibility for scale-up challenges and future recycled waste material streams.

[0081] While the present invention has been particularly shown and described with reference to specific embodiments, it will be understood by those skilled in the art that various changes in form and details can be made therein without departing from the scope of the invention as defined by the appended claims.

Claims

1. 1. A method for recycling a spent catalyst coated membrane, the spent catalyst coated membrane comprising: a membrane comprising a membrane ionomer; a first catalyst layer disposed on one side of the membrane, the first catalyst layer comprising a first catalyst and a first catalyst layer ionomer; and a second catalyst layer disposed on an opposite side of the membrane, the second catalyst layer comprising a second catalyst and a second catalyst layer ionomer, the method comprising: contacting the spent catalyst coated membrane with a solvent to delaminate both the first and second catalyst layers from the membrane without dispersing the membrane, wherein the first and second catalyst layers form a catalyst layer slurry comprising the first catalyst, the first catalyst layer ionomer, the second catalyst, and the second catalyst layer ionomer; Separating the membrane from the catalyst layer slurry; treating the membrane to recover the membrane ionomer; treating the catalyst layer slurry to disperse and recover the first and second catalyst layer ionomers in a solvent, and separating and recovering the first and second catalysts or components thereof.

2. said treating said catalyst layer slurry heating the catalyst layer slurry to disperse the first and second catalyst layer ionomers and form an ionomer dispersion having solid first and second catalyst materials disposed therein; separating the solid first and second catalyst materials from the ionomer dispersion; treating the ionomer dispersion to recover the first and second catalyst layer ionomers; and treating the solid first and second catalytic materials to separate and recover the first and second catalytic materials or components thereof.

3. 3. The method of claim 2, wherein heating the catalyst layer slurry to disperse the first and second catalyst layer ionomers is performed in the same solvent as used to delaminate the first and second catalyst layers from the membrane.

4. 3. The method of claim 2, wherein heating the catalyst layer slurry to disperse the first and second catalyst layer ionomers is performed in a solvent different from a solvent used to delaminate the first and second catalyst layers from the membrane.

5. 5. The method of claim 2, wherein the step of heating the catalyst layer slurry to disperse the first and second catalyst layer ionomers is conducted at a higher temperature than the step of contacting the spent catalyst coated membrane with the solvent to delaminate both the first and second catalyst layers from the membrane without dispersing the membrane.

6. 6. The method of any one of claims 2 to 5, wherein the step of heating the catalyst layer slurry to disperse the first and second catalyst layer ionomers in the solvent is carried out at elevated pressure in an autoclave.

7. 7. The method of any one of claims 1 to 6, wherein treating the catalyst layer slurry further comprises converting the first and second catalyst layer ionomers to a salt form.

8. 8. The method of claim 7, further comprising converting the salt forms of the first and second catalyst layer ionomers back to acid forms by proton exchange.

9. The method of any one of claims 1 to 8, wherein the ionomer dispersion is subjected to ion exchange to remove metal contaminants.

10. 10. The method of any one of claims 1 to 9, wherein the first and second catalyst layer ionomers are recovered from the ionomer dispersion as a blend of the first and second catalyst layer ionomers.

11. The method of any one of claims 1 to 9, wherein the ionomer dispersion is treated to separate the first and second catalyst layer ionomers.

12. 12. The method of any one of claims 1 to 11, wherein the solvent used to delaminate both the first and second catalyst layers from the membrane is a mixture of alcohol and water, wherein the alcohol in the mixture of alcohol and water is selected from n-butanol, n-propanol, i-propanol, or ethanol.

13. 13. The method of claim 12, wherein the mixture of alcohol and water has a volume ratio of alcohol:water of at least 50:50, 60:40, or 70:30; or no more than 95:5, 90:10, or 85:15, or within a range defined by any combination of the foregoing lower and upper limits.

14. 14. The method of any one of claims 1 to 13, wherein the solvent used to delaminate both the first and second catalyst layers from the membrane comprises a base, optionally a metal hydroxide or ammonium solution, to convert the first and second catalyst layer ionomers and the membrane ionomer to a salt form.

15. 15. The method of any one of claims 1 to 14, wherein the solvent is optionally agitated by ultrasonic treatment when contacting the spent catalyst coated membrane with the solvent to delaminate both the first and second catalyst layers from the membrane.

16. The method of any one of claims 1 to 15, wherein the membrane ionomer is different from one or both of the first catalyst layer ionomer and the second catalyst layer ionomer.

17. The method of any one of claims 1 to 16, wherein the first catalyst layer ionomer is different from the second catalyst layer ionomer.

18. The method of any one of claims 1 to 17, wherein the first catalyst comprises platinum, palladium, and / or ruthenium.

19. The method of any one of claims 1 to 18, wherein the second catalyst comprises iridium.

20. 20. The method of any one of claims 1 to 19, wherein the step of treating the solid first and second catalytic materials comprises treating with a heated solution comprising an acid and an oxidizing agent, wherein platinum, palladium, rhodium, and / or ruthenium are leached into the solution, and the solution is separated from the remaining solid components.

21. 21. The method of any one of claims 1 to 20, wherein the step of treating the solid first and second catalytic materials comprises treating with a heated solution comprising an acid and a reducing agent, wherein iridium is leached into the solution, and the solution is separated from the remaining solid components.

22. 21. The method of claim 20, wherein a solid iridium-containing catalytic material is recovered after the leaching of the platinum, palladium, and / or ruthenium and the dispersion of the ionomer.

23. 23. The method of any one of claims 1 to 22, wherein after processing the membrane to recover the membrane ionomer and / or processing the catalyst layer slurry to disperse and recover the first and second catalyst layer ionomers, a spent dispersion medium comprising solvent and fluorine-containing species is produced, the spent dispersion medium is treated to reduce the concentration of fluorine-containing species in the solvent, and the solvent is then discarded or recycled for reuse in processing additional membrane and / or catalyst layer slurry material.

24. 24. The method of claim 23, wherein the treating the spent dispersion medium to reduce the concentration of fluorine-containing species in the solvent comprises one or both of contacting the spent dispersion medium with a solid adsorbent and contacting the spent dispersion medium with one or more ion exchange media.

25. 25. The method of claim 23 or 24, wherein the waste dispersion medium is subjected to cross-flow filtration or ultrafiltration.

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