One-step photochemical closed-loop recovery method for platinum-based catalyst of membrane electrode of hydrogen fuel cell

Abstract

The invention belongs to the field of platinum group metal secondary resource recovery, and discloses a one-step photochemical closed-loop recovery method for a platinum-based catalyst of a hydrogen fuel cell membrane electrode, which is a method for exciting an organic acid ferric salt to oxidize and dissolve the platinum-based catalyst of the hydrogen fuel cell membrane electrode in one step under visible light by using an organic lixivium composed of nitrogen-containing amides and chlorine-containing hydrocarbons. Compared with the prior art, the problems of environmental pollution, redundant recovery operation, high recovery cost, low platinum dissolution rate and the like are solved. According to the method for recycling platinum from the hydrogen fuel cell membrane electrode catalyst, the dissolution rate of precious metal can reach about 95%, the optimal dissolution rate can reach 99% or above, and the method is mild in operation condition, low in energy consumption, environmentally friendly, low in carbon and rich in application scene.

Description

Technical Field

[0001] This invention belongs to the field of secondary resource recycling of platinum group metals, and relates to a method for one-step photochemical dissolution of platinum from hydrogen fuel cell membrane electrode catalysts. In particular, it relates to a method for one-step oxidation dissolution of platinum catalysts for hydrogen fuel cell membrane electrodes by exciting an organic acid iron salt under visible light using an organic leachate composed of nitrogen-containing amides and chlorinated hydrocarbons. Background Technology

[0002] A hydrogen fuel cell is a highly efficient energy conversion device that directly converts hydrogen energy into electrical energy through a reaction. It enables a continuous power generation system with zero emissions and no combustion required; it is not a "battery" in the traditional sense, but rather a continuous power generation system with zero emissions and no combustion. As a core carrier of clean energy technology, hydrogen fuel cells have become a fulcrum supporting energy security, industrial upgrading, and zero-carbon transformation. In a proton exchange membrane hydrogen fuel cell, hydrogen gas is decomposed into protons and electrons under the action of a platinum-based catalyst at the anode. Protons pass through a special polymer membrane to reach the cathode, while electrons form an electric current through an external circuit. Currently, platinum catalysts account for more than 60% of the production cost of fuel cell systems, becoming one of the main bottlenecks to the large-scale popularization of hydrogen fuel cells. Efficiently recovering platinum catalysts from spent fuel cell membrane electrodes can significantly reduce dependence on newly mined platinum mines and substantially reduce raw material costs. At the same time, the energy consumption and carbon emissions of platinum recovery are only 20%-30% of those from mining primary ore, effectively reducing environmental impact. To avoid the risk of heavy metal pollution caused by improper disposal of waste catalysts, to achieve clean production of platinum resources throughout their entire life cycle, to practice the concept of circular economy, and to make hydrogen energy a truly green energy source from "cradle" to "regeneration".

[0003] The perfluorosulfonic acid resin membranes on spent membrane electrodes typically contain 2 wt%-8 wt% platinum, exhibiting extremely strong adhesion to the catalyst coating. Although traditional mechanical separation combined with calcination methods can easily damage the membrane structure, high-temperature calcination leads to a small loss of platinum, resulting in a recovery rate decrease of approximately 40%. Furthermore, high-temperature calcination releases toxic gases such as hydrogen fluoride. One-step wet solvent leaching is currently a more effective and convenient method for recovering platinum from spent membrane electrodes. Traditional leaching systems mainly consist of strong acids and strong oxidants, including the aqua regia method (HCl / HNO3), the chlorination method (HCl / Cl2), and the oxidation method (HCl / H2O2), etc. (Duclos L, Svecova L, Laforest V, Mandil G, Thivel P X. Hydrometallurgy. 2016, 160, 79-89). However, using highly corrosive solvents generates toxic waste liquid, and the platinum recovery rate is only 80%-90%. Perfluorosulfonic acid resins are extremely chemically stable and cannot be degraded by traditional processes, posing a potential risk of water pollution. Hodnik et al. proposed an induced surface potential modulation strategy. This method achieves periodic modulation of the metal surface potential through alternating exposure to ozone and carbon monoxide, thereby dissolving the platinum electrode in low-concentration hydrochloric acid. This transient platinum dissolution controls the gas-induced surface potential, thus eliminating the dependence on conductive substrates and the external circuitry inherent in traditional electrochemical dissolution. (Hodnik N, Baldizzone C, Polymeros G, Geiger S, Grote J, Cherevko S, Mingers A, Zeradjanin A, Mayrhofer KJ J. Nature Communication. 2016, 7, 13164). However, this method is highly theoretical, and further research is needed on its practical application in waste treatment. Xie et al. developed a method using decatungstate as a catalyst to oxidize platinum on a waste membrane electrode via a photocatalytic reaction in a mixture of acetonitrile and dichloromethane, thus achieving green recycling (Xie Y, Zhang T, Guo H, Ding Z, Dong S, Chen Y, Zhang J, Guan S; Xu Z, Yu H, Bian Z. Angewandte Chemie International Edition. 2025, 64, e202505651). This method requires targeted synthesis of a solid catalyst, resulting in high raw material costs, but the method of converting light energy into chemical energy to oxidize platinum warrants further investigation.

[0004] Looking at existing patents on photochemical methods for recovering platinum from catalysts, CN119876616A discloses a method for recovering the precious metal platinum from a highly hydrophobic proton exchange membrane fuel cell. This method involves pretreating the membrane electrode with an organic alkyd aqueous solvent, followed by dissolving platinum using ferric oxalate complexes and iodides. However, this is essentially a two-step process, failing to achieve the simplicity of a one-step method and increasing the number of steps in the production process. CN111809063B discloses a photocatalytic metal dissolution method, primarily using solid materials such as TiO2 as photocatalysts to photocatalytically recover platinum and other precious metals within cyano compounds or organic chlorides. However, subsequent research revealed that this method has low platinum recovery efficiency on the membrane electrode catalyst. CN115717198B discloses a method for leaching platinum group metals from spent catalysts using ultraviolet-visible light. This method uses ferric oxalate complexes / hydrogen peroxide-chloride salts as solvents to recover platinum under ultraviolet light conditions. However, the pure aqueous phase composition of this method reduces the recovery performance of hydrophobic membrane materials.

[0005] While existing technologies offer several potential wet recovery techniques for platinum from spent membrane electrode catalysts, these technologies still suffer from problems such as solvent toxicity, cumbersome processes, poor platinum leaching efficiency, limited oxidation capacity, and high production costs. Therefore, finding a green, efficient, and reusable wet recovery method for platinum from spent hydrogen fuel cell membrane electrode catalysts is crucial. Summary of the Invention

[0006] The purpose of this invention is to propose a green, efficient, and stable method for photochemical leaching of platinum from spent hydrogen fuel cell membrane electrode catalysts, and a closed-loop recovery method for using the platinum leachate in the preparation of membrane electrode catalysts, thereby achieving low-cost application of platinum in fuel cells. On the one hand, this avoids secondary pollution from hazardous waste and effectively reduces the manufacturing cost of platinum-based membrane electrodes. On the other hand, it avoids the environmental pollution caused by the use of highly corrosive and toxic chemicals.

[0007] The inventive aspect of this invention—the one-step photochemical closed-loop recovery method for platinum-based catalysts in hydrogen fuel cell membrane electrodes—lies in the phototriggered decomposition of iron salts from organic acids. • OH and other reactive free radicals can stimulate chlorine-containing organic compounds to produce compounds with higher reactivity with platinum. • Cl radicals. Simultaneously, nitrogen-containing amide reagents can act as strippers for the membrane material during platinum dissolution. This allows for one-step recovery of platinum from the membrane electrode catalyst. The noble metal dissolution rate of the method described in this invention can reach over 95%.

[0008] The technical solution of this invention:

[0009] A one-step photochemical closed-loop recovery method for platinum-based catalysts in hydrogen fuel cell membrane electrodes involves a photochemical oxidation reaction of an organic acid iron salt-nitrogen-containing amide organic compound-chlorine-containing organic compound leaching system under visible light to dissolve platinum in the membrane electrode catalyst. Simultaneously, the platinum leachate is used to prepare an electrochemical hydrogen evolution reaction membrane electrode catalyst to achieve a closed-loop recycling application of platinum resources throughout their entire life cycle.

[0010] Includes the following steps:

[0011] (1) Cut the waste membrane electrode catalyst into sheets for later use;

[0012] (2) Preparation of organic acid iron salt complex solution: Deionized water is used as solvent, organic acid and iron oxide are used as solutes, the solid-liquid ratio of organic acid to water is 5:1~200:1 g:L, the solid-liquid ratio of iron oxide to water is 3:1~20:1 g:L, and the mixture is stirred in an oil bath at 70~98 ℃ for 6~12 h at a stirring rate of 300~100 r / min to obtain an organic acid iron salt complex solution with an organic acid concentration of 15~30 g / L;

[0013] (3) Preparation of organic acid ferric salt-nitrogen-amide organic compound-organochloride leaching agent: Add the organic acid ferric salt complex solution to the mixture of nitrogen-amide organic compound and organochloride, control the volume fraction of the organic acid ferric salt complex solution to be 20~75 vol.%, control the volume fraction of nitrogen-amide organic compound to be 10~30 vol.%, and control the volume fraction of organochloride to be 15~50 vol.%; stir at 20~25℃ for 5~35 min at a stirring rate of 300~500 r / min to obtain the organic acid ferric salt-nitrogen-amide organic compound-organochloride leaching agent;

[0014] (4) Leaching of precious metals: The sheet-like waste membrane electrode catalyst obtained in step (1) is added to the organic acid iron salt complex-nitrogen-containing amide organic matter-organochloride leaching agent obtained in step (3). The sheet-like waste membrane electrode catalyst (cm 2 The ratio of organic acid iron salt complex - nitrogen-containing amide organic matter - organochlorine leaching agent (L) is 20:1~100:1. The mixture is stirred for 10~600 min under light conditions at a stirring rate of 300~500 r / min to obtain a mixture.

[0015] (5) Separation, enrichment and closed-loop utilization of precious metal recovery solution: The mixture obtained in step (4) is subjected to solid-liquid two-phase separation. The liquid phase is the precious metal recovery solution, and the solid phase is the organic acid ferrous salt precipitate and membrane carrier. After liquid-liquid separation and heating distillation of the liquid phase, the solution enriched with Pt is collected and the leachate is prepared again. This process is repeated to dissolve and recover Pt, thereby achieving Pt enrichment. The 50-80 mg·L⁻¹ obtained after enrichment is used to extract the Pt component.-1 The Pt recovery solution was recoated onto carbon paper, and the platinum loading on the carbon paper was controlled at 0.3–0.4 mg / cm³. 2 The catalyst was reduced in a hydrogen atmosphere at 300-500℃ for 3-6 h. The newly prepared hydrogen evolution membrane electrode catalyst was then vacuum dried at 30-60℃ and used for hydrogen evolution reaction stability testing. The organic acid ferrous salt precipitate was dried at 50-80℃ for 6-12 h and then calcined at 400-600℃ for 2-4 h to obtain secondary recovered iron oxide, which can be recycled as a reactant for the preparation of organic acid ferrous salt complexes.

[0016] The aforementioned spent membrane electrode catalyst is derived from spent hydrogen fuel cell membrane electrode platinum-based catalysts, and its surface coating mainly consists of Pt / C, PtRu / C, and PtCo / C (Pt 0.3~0.4 mg / cm³). 2 ).

[0017] The illumination uses a xenon lamp with a wavelength range of 300~2500nm and a light intensity of 80~300 mW / cm². 2 .

[0018] The organic acid iron salt complex is at least one of ferric oxalate, ferric citrate, and ferric tartrate.

[0019] The nitrogen-containing amide organic compound is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, and N-methylpyrrolidone.

[0020] The organochloride is at least one of dichloromethane, chloroform, carbon tetrachloride, and chlorobenzene.

[0021] The organic acid iron salt complex-nitrogen-containing amide organic compound-organochloride leaching agent can produce highly reactive substances under light conditions. • OH free radicals and • The formation process of Cl radicals, taking the ferric oxalate complex-N,N-dimethylformamide-dichloromethane system as an example, is as follows:

[0022]

[0023]

[0024]

[0025]

[0026] Ultimately, the system possesses sufficient conditions for platinum oxidation and dissolution due to the self-generated free radical reactive oxides. In this process, the organic acid-iron salt complexes act as oxidants and initiators, the nitrogen-containing amide organic compounds play a role in stripping and promoting dissolution, and the organochlorides act as oxidants and complexing agents.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) This invention utilizes the photogenerated free radical properties of organic acid iron salt complexes, enabling them to function as both metal oxidants and chlorine free radical initiators. Free radicals stimulate the generation of new chlorine free radicals from organic chlorides, while nitrogen-containing amide organics are stripped of the catalytically active layer within the membrane material during the recovery process. This effectively enhances the one-step platinum leaching capability of the system, thereby avoiding the two-step treatment of the stripping agent and achieving effective leaching and recovery of platinum from the waste (recovery rate ≥ 95%).

[0029] (2) This invention utilizes the strong binding effect and reactivity of hydroxyl radicals and chlorine radicals on platinum to obtain platinum leachate for the preparation and utilization of electrochemical hydrogen evolution membrane electrode catalyst, thereby realizing the closed-loop application of platinum recovery for efficient and stable electrode catalyst.

[0030] (3) All reagents used in this invention are chemically mild and low-cost. The reaction is carried out under normal temperature and pressure photochemical conditions, which can achieve energy conservation and emission reduction and avoid secondary pollution of the environment. The solid by-products produced can be recycled and reused and the separation operation is simple, which greatly reduces the cost of pollutant treatment and reduces resource consumption. Attached Figure Description

[0031] Figure 1 This is an actual appearance diagram of the platinum-based catalyst for an untreated, waste hydrogen fuel cell membrane electrode assembly.

[0032] Figure 2 The reaction stability of the fresh catalyst for the hydrogen evolution reaction membrane electrode prepared for platinum recovery solution; where a represents the reaction stability of the prepared membrane electrode catalyst at 500 mA·cm⁻¹. -2 The reaction stability at a current density of 5 hours, b represents the prepared membrane electrode catalyst at 200 mA·cm⁻¹. -2 The reaction stability after 10 hours of reaction at the current density. Detailed Implementation

[0033] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0034] The photochemical recovery process of platinum using the organic acid iron salt-nitrogen-containing amide organic matter-organochloride leaching system described in this invention specifically includes the following steps:

[0035] (1) Cut the membrane electrode catalyst into a certain size;

[0036] (2) Mix the waste catalyst sample obtained in step (1) with the organic acid iron salt-nitrogen-containing amide organic matter-organochloride leaching agent in an appropriate ratio, and place it under a xenon lamp (300~2500 nm, 80~300 mW / cm²). 2 Stir for an appropriate time until the reaction is complete, and a solid-liquid two-phase product is obtained.

[0037] (3) The solid-liquid products obtained in step (2) are separated by centrifugation or filtration. The liquid phase is a platinum-containing leachate, and the solid phase is a precipitate of divalent organic acid iron salt. The solid precipitate is further calcined to become raw material iron oxide.

[0038] Examples 1-22 and Comparative Examples 1-7 all use the process flow shown above.

[0039] The platinum content in the waste used in Examples 1-22 and Comparative Examples 1-7 ranged from 0.3 to 0.4 mg / cm³. 2 .

[0040] Example 1

[0041] (1) Take a membrane electrode catalyst containing 0.3 mg Pt / C as the catalyst layer and cut it into sheets for later use;

[0042] (2) Take 20 vol.% ferric oxalate complex, 30 vol.% N,N-dimethylformamide and 50 vol.% dichloromethane, mix them evenly to form the membrane electrode platinum catalyst leaching agent;

[0043] (3) Mix the leaching system obtained in step (2) with the waste prepared in step (1) until homogeneous. Stir under visible light for 300 min at a stirring rate of 300 r / min.

[0044] (4) The product obtained in step (3) is subjected to solid-liquid two-phase separation. The liquid phase is collected in a reagent bottle and recorded as platinum leaching solution. A certain amount of the precious metal leaching solution is recoated onto a 1.0 cm layer. 2 On carbon paper, after reduction at 400℃ under a hydrogen atmosphere for 3 h, the platinum loading was 0.3 mg / cm³. 2 The newly prepared hydrogen evolution membrane electrode catalyst was then vacuum dried at 60 °C and used for hydrogen evolution reaction stability testing. The solid phase consisted of ferrous oxalate and the membrane support, which were dried at 60 °C for 12 h and then calcined at 500 °C for 4 h to obtain secondary recovered iron oxide.

[0045] Example 2

[0046] In this embodiment, the volume fraction of the added iron oxalate complex in Example 1 was replaced from 20 vol.% to 55 vol.%, and the volume fraction of the added dichloromethane was replaced from 50 vol.% to 15 vol.%, while other conditions were exactly the same as in Example 1.

[0047] Example 3

[0048] In this embodiment, the volume fraction of the added iron oxalate complex in Example 1 was replaced from 20 vol.% to 40 vol.%, and the volume fraction of the added N,N-dimethylformamide was replaced from 30 vol.% to 10 vol.%, while other conditions were exactly the same as in Example 1.

[0049] Example 4

[0050] In this embodiment, the volume fraction of the added iron oxalate complex in Example 1 was replaced from 20 vol.% to 75 vol.%, the volume fraction of the added N,N-dimethylformamide was replaced from 30 vol.% to 10 vol.%, and the volume fraction of the added dichloromethane was replaced from 50 vol.% to 15 vol.%, while other conditions were exactly the same as in Example 1.

[0051] Example 5

[0052] In this embodiment, the volume fraction of the ferric oxalate complex in the solution of Example 1 was replaced from 20 vol.% to 40 vol.%, and the volume fraction of dichloromethane was replaced from 50 vol.% to 30 vol.%, while other conditions were exactly the same as in Example 1.

[0053] Example 6

[0054] In this embodiment, the volume fraction of the added iron oxalate complex in Example 1 was replaced from 20 vol.% to 60 vol.%, the volume fraction of the added N,N-dimethylformamide was replaced from 30 vol.% to 10 vol.%, and the volume fraction of the added dichloromethane was replaced from 50 vol.% to 30 vol.%, while other conditions were exactly the same as in Example 1.

[0055] Example 7

[0056] In this embodiment, the volume fraction of the added iron oxalate complex in Example 1 was replaced from 20 vol.% to 65 vol.%, the volume fraction of the added N,N-dimethylformamide was replaced from 30 vol.% to 20 vol.%, and the volume fraction of the added dichloromethane was replaced from 50 vol.% to 15 vol.%, while other conditions were exactly the same as in Example 1.

[0057] Example 8

[0058] In this embodiment, the volume fraction of the added iron oxalate complex in Example 1 was replaced from 20 vol.% to 30 vol.%, and the volume fraction of the added N,N-dimethylformamide was replaced from 30 vol.% to 20 vol.%, while other conditions were exactly the same as in Example 1.

[0059] Example 9

[0060] In this embodiment, the illumination of the entire visible light wavelength range in Embodiment 1 is replaced with actual sunlight illumination, while other conditions are exactly the same as in Embodiment 1.

[0061] Example 10

[0062] In this embodiment, the ferric oxalate complex in Example 1 is replaced with the ferric citrate complex, and all other conditions are exactly the same as in Example 1.

[0063] Example 11

[0064] In this embodiment, the ferric oxalate complex in Example 1 is replaced with the ferric tartrate complex, and all other conditions are exactly the same as in Example 1.

[0065] Example 12

[0066] In this embodiment, N,N-dimethylformamide (DMF) in Example 1 is replaced with N,N-dimethylacetamide (DMA), and all other conditions are exactly the same as in Example 1.

[0067] Example 13

[0068] In this embodiment, N,N-dimethylformamide (DMF) in Example 1 is replaced with N,N-diethylformamide (DEF), and all other conditions are exactly the same as in Example 1.

[0069] Example 14

[0070] In this embodiment, N,N-dimethylformamide (DMF) in Example 1 is replaced with N-methylpyrrolidone (NMP), and all other conditions are exactly the same as in Example 1.

[0071] Example 15

[0072] In this embodiment, dichloromethane (CH2Cl2) in Example 1 is replaced with chloroform (CHCl3), and all other conditions are exactly the same as in Example 1.

[0073] Example 16

[0074] In this embodiment, dichloromethane (CH2Cl2) in Example 1 is replaced with carbon tetrachloride (CCl4), and all other conditions are exactly the same as in Example 1.

[0075] Example 17

[0076] In this embodiment, dichloromethane (CH2Cl2) in Example 1 is replaced with chlorobenzene (PhCl), and all other conditions are exactly the same as in Example 1.

[0077] Example 18

[0078] This embodiment will use Pt / C (Pt 0.3 mg / cm³) from Example 1. 2 The membrane electrode catalyst with PtRu / C (Pt 0.3 mg / cm³) as the catalyst layer was replaced with a catalyst with PtRu / C (Pt 0.3 mg / cm³). 2 The membrane electrode catalyst is the catalyst layer, and other conditions are exactly the same as in Example 1.

[0079] Example 19

[0080] This embodiment will use Pt / C (Pt 0.3 mg / cm³) from Example 1. 2 The membrane electrode catalyst with PtCo / C (Pt 0.3 mg / cm³) as the catalyst layer was replaced with a catalyst with PtCo / C (Pt 0.3 mg / cm³) as the catalyst layer. 2 The membrane electrode catalyst is the catalyst layer, and other conditions are exactly the same as in Example 1.

[0081] Example 20

[0082] In this embodiment, the light stirring in Example 1 is replaced with 10 min instead of 300 min, while other conditions are exactly the same as in Example 1.

[0083] Example 21

[0084] In this embodiment, the light stirring in Example 1 is replaced with 150 min instead of 300 min, while other conditions are exactly the same as in Example 1.

[0085] Example 22

[0086] In this embodiment, the light stirring in Example 1 is replaced with 600 min instead of 300 min, while other conditions are exactly the same as in Example 1.

[0087] Comparative Example 1

[0088] Compared with Example 1, this comparative example did not add ferric oxalate (0 vol.%), and all other conditions were exactly the same as in Example 1.

[0089] Comparative Example 2

[0090] Compared with Example 1, this comparative example did not contain N,N-dimethylformamide (DMF) (0 vol.%), and all other conditions were exactly the same as in Example 1.

[0091] Comparative Example 3

[0092] Compared with Example 1, this comparative example did not add dichloromethane (CH2Cl2) (0 vol.%), and all other conditions were exactly the same as in Example 1.

[0093] Comparative Example 4

[0094] Compared with Example 1, this comparative example was reacted in the dark without the addition of light, while all other conditions were exactly the same as in Example 1.

[0095] Comparative Example 5

[0096] Compared with Example 1, dichloromethane (CH2Cl2) in this comparative example was replaced with sodium chloride (NaCl), while all other conditions were exactly the same as in Example 1.

[0097] Comparative Example 6

[0098] Compared to Example 17, this comparative example uses N,N-dimethylformamide (DMF) instead of urea, while all other conditions are exactly the same as in Example 1.

[0099] The precious metal recovery solutions obtained in Examples 1-22 and Comparative Examples 1-6 were detected by inductively coupled plasma optical emission spectrometry (ICP-OES), and the precious metal dissolution rate was calculated.

[0100] The formula for calculating the leaching rate of precious metals is as follows:

[0101]

[0102] The photocatalytic dissolution conditions of the methods described in Examples 1-22 and Comparative Examples 1-6 are shown in Table 1:

[0103] Table 1

[0104]

[0105] The dissolution rates of precious metals in the methods described in Examples 1-22 and Comparative Examples 1-6 are shown in Table 2:

[0106] Table 2

[0107]

[0108] Comparative Examples 1-8 show that the present invention uses ferric oxalate complex, N,N-dimethylformamide, and dichloromethane in volume ratios of 20-75 vol.%, 10-30 vol.%, and 15-50 vol.%, respectively. The optimal recovery rate (vol.%) is not less than 99%, and the average recovery rate is greater than 95%. Comparisons with Examples 1 and 9 show that this system can achieve a platinum recovery rate close to 99% even under sunlight. Comparisons with Examples 1, 10, and 11 show that as the acidity of the organic acid changes, the recovery rate of its organic acid iron salt complex for platinum decreases to approximately 95-96%, with ferric oxalate being the optimal organic acid iron salt. Comparisons with Examples 1 and 12-14 show that N,N-dimethylformamide is the most suitable nitrogen-containing amide organic compound. Comparisons with Examples 1 and 15-17 show that dichloromethane is the most suitable organochlorine. Comparisons with Examples 1, 18, and 19 show that this method is generally applicable to the recovery of different types of platinum-based membrane electrode catalysts, with a recovery rate close to 99%. Comparisons with Examples 20-22 show that the platinum recovery rate increases with reaction time, exhibiting a rapid reaction phase from 10 to 150 min, a stable reaction phase from 150 to 300 min, and a stable recovery phase from 300 to 600 min. The reaction is in its final stage. Comparative Examples 1 and 1-4 show that organic acid iron salts, nitrogen-containing amide organic compounds, organic chlorides, and light conditions are key factors for the efficient dissolution of platinum using this method. Comparative Examples 1 and 5 show that inorganic chlorides have a limited effect in this leaching system, while organic chlorides are more suitable. Comparative Examples 1 and 6 show that nitrogen-containing organic compounds generally cannot promote platinum dissolution.

[0109] As can be seen from the test results of the above embodiments and comparative examples, the method for recovering platinum from the platinum-based catalyst of the hydrogen fuel cell membrane electrode according to the present invention can achieve a platinum dissolution rate of over 95%, with the optimal dissolution rate reaching over 99%. At the same time, the method of the present invention has mild operating conditions, low energy consumption, is green and low-carbon, and has a wide range of applicable scenarios.

[0110] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A one-step photochemical closed-loop recovery method for platinum-based catalysts in hydrogen fuel cell membrane electrode assemblies, characterized in that, Includes the following steps: (1) Cut the waste membrane electrode catalyst into sheets for later use; (2) Preparation of organic acid iron salt complex solution: Deionized water is used as solvent, organic acid and iron oxide are used as solutes, the solid-liquid ratio of organic acid to water is 5:1~200:1 g:L, the solid-liquid ratio of iron oxide to water is 3:1~20:1 g:L, and the mixture is stirred in an oil bath at 70~98 ℃ for 6~12 h at a stirring rate of 300~100 r / min to obtain an organic acid iron salt complex solution with an organic acid concentration of 15~30 g / L; (3) Preparation of organic acid ferric salt-nitrogen-amide organic compound-organochloride leaching agent: Add the organic acid ferric salt complex solution to the mixture of nitrogen-amide organic compound and organochloride, control the volume fraction of the organic acid ferric salt complex solution to be 20~75 vol.%, control the volume fraction of nitrogen-amide organic compound to be 10~30 vol.%, and control the volume fraction of organochloride to be 15~50 vol.%; stir at 20~25℃ for 5~35 min at a stirring rate of 300~500 r / min to obtain the organic acid ferric salt-nitrogen-amide organic compound-organochloride leaching agent; (4) Leaching of precious metals: The sheet-like waste membrane electrode catalyst obtained in step (1) is added to the organic acid iron salt complex-nitrogen-containing amide organic matter-organochloride leaching agent obtained in step (3). The sheet-like waste membrane electrode catalyst cm 2 The ratio of organic acid iron salt complex - nitrogen-containing amide organic matter - organochloride leaching agent L is 20:1~100:

1. The mixture is stirred for 10~600 min under light conditions at a stirring rate of 300~500 r / min to obtain a mixture. (5) Separation, enrichment and closed-loop utilization of precious metal recovery liquid: The mixture obtained in step (4) is subjected to solid-liquid two-phase separation. The liquid phase is precious metal recovery liquid, and the solid phase is organic acid divalent iron salt precipitate and membrane carrier. After liquid-liquid separation and heating distillation of the liquid phase, the solution enriched with Pt component is collected and the leachate is prepared again. This process is repeated to dissolve and recover Pt to achieve enrichment. The enriched 50-80 mg·L -1 The Pt recovery solution was recoated onto carbon paper, and the platinum loading on the carbon paper was controlled at 0.3–0.4 mg / cm³. 2 The catalyst was reduced in a hydrogen atmosphere at 300-500℃ for 3-6 h; then the newly prepared hydrogen evolution membrane electrode catalyst was dried under vacuum at 30-60℃ and used for hydrogen evolution reaction stability testing. After drying the organic acid ferrous salt precipitate at 50-80℃ for 6-12 h, it is calcined at 400-600℃ for 2-4 h to obtain secondary recovered iron oxide, which can be recycled as a reactant for preparing organic acid ferrous salt complexes.

2. The one-step photochemical closed-loop recovery method for platinum-based catalysts in hydrogen fuel cell membrane electrodes according to claim 1, characterized in that, The spent membrane electrode catalyst is derived from the platinum-based catalyst of the spent hydrogen fuel cell membrane electrode, and its surface coating is mainly composed of Pt / C, PtRu / C and PtCo / C.

3. The one-step photochemical closed-loop recovery method for platinum-based catalysts in hydrogen fuel cell membrane electrodes according to claim 1, characterized in that, The illumination uses a xenon lamp with a wavelength range of 300~2500nm and a light intensity of 80~300 mW / cm². 2 .

4. The one-step photochemical closed-loop recovery method for platinum-based catalysts in hydrogen fuel cell membrane electrodes according to claim 1, characterized in that, The organic acid iron salt complex is at least one of ferric oxalate, ferric citrate, and ferric tartrate.

5. The one-step photochemical closed-loop recovery method for platinum-based catalysts in hydrogen fuel cell membrane electrodes according to claim 1, characterized in that, The nitrogen-containing amide organic compound is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, and N-methylpyrrolidone.

6. The one-step photochemical closed-loop recovery method for platinum-based catalysts in hydrogen fuel cell membrane electrodes according to claim 1, characterized in that, The organochloride is at least one of dichloromethane, chloroform, carbon tetrachloride, and chlorobenzene.

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