A method for preparing a monatomic photocatalyst from lithium ion battery waste material, and products and applications thereof

Abstract

The application discloses a method for preparing a single-atom photocatalyst from lithium ion battery waste, and products and applications thereof. The method comprises the following steps: pretreating waste ternary lithium batteries to obtain waste containing positive and negative electrode materials; performing oxygen-free roasting on the waste; performing selective extraction on the waste by using carbon dioxide water; filtering to obtain a filtrate and waste residue; evaporating and crystallizing the filtrate to obtain lithium carbonate; performing acid leaching on the waste residue to obtain a mixed metal solution; reacting the mixed metal solution with melamine and sulfuric acid to form a supramolecular precursor; and performing oxygen-free roasting on the precursor to obtain a single-atom photocatalyst. The method directly utilizes waste lithium ion batteries to prepare a high-performance single-atom photocatalyst, avoids a complicated metal separation and recovery process, and simultaneously obtains two high-value-added products, namely, lithium carbonate and a single-atom photocatalyst, and has important environmental, economic and social significance. Moreover, the method has the characteristics of low raw material cost, simple process and easy industrial application.

Description

Technical Field

[0001] This invention belongs to the field of waste lithium battery resource utilization and catalytic materials, and specifically relates to a method, product and application of preparing single-atom photocatalysts using waste lithium-ion batteries as raw materials. Background Technology

[0002] Lithium-ion batteries are widely used in electric vehicles, energy storage stations, and other fields due to their advantages such as high energy density, long cycle life, and fast charge / discharge speed. Especially with the booming development of the new energy industry, the demand for lithium-ion batteries is increasing rapidly. However, this has led to a large number of waste batteries needing disposal. It is estimated that by 2030, the global amount of waste lithium-ion batteries will exceed 11 million tons, representing a market worth hundreds of billions of dollars. Since the organic electrolytes, heavy metals, and lithium salts contained in waste lithium-ion batteries can cause serious environmental pollution, their recycling is of great practical significance. Current recycling steps typically include: pretreatment, metal leaching, metal separation, and purification. For ternary lithium batteries, a leaching solution containing lithium, nickel, cobalt, and manganese is usually obtained. Subsequent separation and purification processes require complex steps, resulting in high costs and low product recovery rates. To address this issue, directly using recycled waste lithium-ion batteries to produce other high-value-added products has become a focus of research in recent years.

[0003] Photocatalysis technology has wide applications in the energy and environmental fields. Because it can directly utilize solar energy, it is considered a green technology. Developing efficient, stable, and low-cost photocatalytic materials has become crucial in this field. The most common photocatalyst is nano-titanium dioxide, but its light utilization is limited, only absorbing the ultraviolet portion of sunlight, thus restricting its applications. In recent years, carbon nitride has attracted attention due to its good visible light absorption capacity. However, it exhibits poor catalytic performance due to a lack of active sites, difficulty in electron-hole separation, and easy recombination. Therefore, finding new methods to improve the catalytic activity of carbon nitride remains a major challenge.

[0004] Currently, there is a lack of a method to directly synthesize single-atom-loaded photocatalysts from lithium battery waste without the need for metal separation. Summary of the Invention

[0005] The primary objective of this invention is to overcome the shortcomings and deficiencies of existing technologies and provide a method for preparing single-atom photocatalysts using lithium-ion battery waste as raw material. This method first utilizes a carbothermal reduction-water leaching lithium extraction process to recover high-value-added lithium carbonate, and then recovers a nickel-cobalt-manganese mixed metal solution through acid leaching. Next, the mixed metal solution is directly added to a solution containing melamine and dilute sulfuric acid for a hydrothermal reaction to synthesize a supramolecular precursor. Through anaerobic calcination, the supramolecular precursor is then converted into a single-atom photocatalyst consisting of nickel-cobalt-manganese mixed single-atom components co-supported with carbon nitride nanosheets. This process solves the current complex separation process required in lithium battery recycling, and the prepared high-value-added single-atom photocatalyst exhibits excellent performance in photocatalytic hydrogen production, overcoming the problem of low photocatalytic efficiency in traditional catalysts. This process is simple, low-cost, and low-polluting, converting waste ternary lithium batteries into high-value-added lithium carbonate and single-atom photocatalysts, and has great industrial application potential.

[0006] Another object of the present invention is to provide a single-atom photocatalyst obtained by the above method.

[0007] Another object of the present invention is to provide the application of the above-mentioned single-atom photocatalyst.

[0008] The objective of this invention is achieved through the following technical solution: a method for preparing single-atom photocatalysts using lithium-ion battery waste as raw material, comprising the following steps:

[0009] (1) Pre-treatment of waste batteries: The recycled waste ternary lithium batteries are dried, crushed and sorted to obtain waste containing positive electrode materials and negative electrode materials;

[0010] (2) Recovering lithium carbonate: The waste obtained in step (1) is roasted at high temperature under anaerobic conditions. Then, the roasted product is extracted for lithium by water leaching. During the water leaching process, CO2 is continuously introduced to promote the dissolution of lithium ions. The leachate containing lithium ions and the waste residue containing nickel, cobalt and manganese are obtained by filtration. The leachate is evaporated, crystallized and filtered to obtain white powdered lithium carbonate.

[0011] (3) Preparation of single-atom photocatalysts:

[0012] A. The waste residue containing nickel, cobalt and manganese obtained in step (2) is leached in sulfuric acid solution and filtered to obtain a mixed metal solution containing nickel, cobalt and manganese and carbon slag.

[0013] B. Melamine, sulfuric acid, water, and the mixed metal solution containing nickel, cobalt, and manganese obtained in step A are mixed and reacted; this reaction partially converts melamine into cyanuric acid, forming a mixture.

[0014] C. The mixture obtained in step B is subjected to a hydrothermal reaction, and the precipitate is separated from the product; the precipitate is washed and dried to obtain a supramolecular precursor;

[0015] D. The supramolecular precursor obtained in step C is calcined at high temperature under anaerobic conditions to obtain a single-atom photocatalyst.

[0016] The drying temperature in step (1) is preferably 250-350°C; more preferably 300°C.

[0017] The crushing process described in step (1) is preferably mechanical crushing.

[0018] The oxygen-free conditions described in step (2) are preferably obtained by filling with an inert gas.

[0019] The inert gas is one or both of nitrogen or helium; more preferably nitrogen.

[0020] The conditions for high-temperature calcination in step (2) are preferably calcination at 700-850°C for 1-5 hours; more preferably calcination at 800°C for 3-5 hours; and even more preferably calcination at 800°C for 4 hours.

[0021] The CO2 flow rate in step (2) is preferably 30-80 mL / min per liter of water; more preferably 50-80 mL / min per liter of water.

[0022] The water is preferably added at a ratio of water to waste (L:g) of 1:30 to 70; more preferably at a ratio of water to waste (L:g) of 1:50.

[0023] The leaching conditions described in step (2) are preferably 1 to 3 hours at room temperature; more preferably 2 hours at room temperature.

[0024] The concentration of the sulfuric acid solution mentioned in step (3)A is preferably 2.0 to 6.0 mol / L; more preferably 4.0 mol / L.

[0025] The amount of sulfuric acid solution used in step (3)A is preferably calculated as 40-80g:1L for waste residue containing nickel, cobalt, and manganese and sulfuric acid solution; more preferably calculated as 60g:1L for waste residue containing nickel, cobalt, and manganese and sulfuric acid solution.

[0026] The leaching temperature in step (3)A is preferably 60-90°C; more preferably 80°C.

[0027] The leaching time in step (3)A is preferably 2 to 4 hours; more preferably 3 hours.

[0028] The melamine, sulfuric acid, water, and the mixed metal solution containing nickel, cobalt, and manganese obtained in step (3)B are preferably mixed in the ratio of (6-10)g:(1-5)mL:(80-120)mL:(0.1-4.0)mL; more preferably in the ratio of (7-9)g:(2-4)mL:(90-110)mL:(0.1-2.0)mL; and most preferably in the ratio of 8g:3mL:100mL:(0.1-1.0)mL.

[0029] The sulfuric acid mentioned in step (3)B is sulfuric acid with a concentration of 98% by volume.

[0030] The reaction conditions described in step (3)B are preferably 60-90°C for 30-120 min; more preferably 80°C for 60 min.

[0031] Step (3)B is more preferably: melamine and sulfuric acid are added to water and mixed to carry out a pre-reaction, and then the mixed metal solution containing nickel, cobalt and manganese obtained in step A is added to continue the reaction.

[0032] The preferred pre-reaction conditions are a reaction at 60–100°C for 5–15 min; more preferably, a reaction at 80°C for 10 min.

[0033] The preferred conditions for the continued reaction are a reaction at 60–100°C for 25–55 min; more preferably, a reaction at 80°C for 50 min.

[0034] The hydrothermal reaction conditions described in step (3)C are preferably 160-200°C for 1-24 hours; more preferably 180°C for 20 hours.

[0035] The preferred solvent for washing in step (3)C is deionized water.

[0036] The number of washes in step (3)C is preferably 1 to 5 times; more preferably 3 times.

[0037] The oxygen-free conditions described in step (3)D are preferably obtained by filling with an inert gas.

[0038] The inert gas is one or both of nitrogen or helium; more preferably nitrogen.

[0039] The preferred conditions for high-temperature calcination in step (3)D are calcination at 500-600°C for 2-6 hours; more preferably, calcination at 550°C for 4 hours.

[0040] A single-atom photocatalyst was prepared by the above method. This single-atom photocatalyst can achieve photocatalytic hydrogen production, exhibits good responsiveness to visible light, has a stable structure that is not easily deactivated, good cycle stability, and low synthesis cost.

[0041] The application of the above-mentioned single-atom photocatalysts in photocatalytic hydrogen production.

[0042] The light is preferably sunlight.

[0043] Compared with existing technologies, the present invention has the following advantages and beneficial effects:

[0044] (1) This invention uses waste materials from discarded ternary lithium batteries as raw materials to directly prepare high-value-added single-atom catalysts. The synthesis cost is low and much lower than that of traditional platinum catalysts.

[0045] (2) Mixed metals (nickel, cobalt, manganese) are difficult to separate during lithium battery recycling due to their similar chemical properties, which usually results in high costs. This invention utilizes multi-metal co-loading to avoid the metal separation process.

[0046] (3) The single-atom supported nanosheet photocatalyst prepared in this invention can achieve a significant improvement in catalytic performance with extremely low loading, and has great atom economy;

[0047] (4) The catalytic performance of the multi-metal co-supported nanosheet catalyst is greatly improved. Attached Figure Description

[0048] Figure 1 This is a process route diagram for preparing single-atom photocatalysts using lithium battery waste as raw materials according to the present invention.

[0049] Figure 2 This is a transmission electron microscope image with spherical aberration correction of the single-atom photocatalyst prepared in Example 2.

[0050] Figure 3 The images shown are electron microscope (EM) images of the single-atom photocatalyst prepared in Example 2; where a is a scanning electron microscope (SEM-EDS) image and b is a transmission electron microscope (TEM-EDS) image.

[0051] Figure 4 The image shows the X-ray diffraction (XRD) pattern of the single-atom photocatalyst prepared in this invention; where BCN represents bulk carbon nitride, UCN represents ultrathin carbon nitride nanosheets, and NiCoMn-UCN represents mixed metal-ultrathin carbon nitride nanosheets.

[0052] Figure 5 The image shows the photocatalytic hydrogen production effect of the catalyst prepared in this invention; where BCN represents bulk carbon nitride, UCN represents ultrathin carbon nitride nanosheets, and NiCoMn-UCN represents mixed metal-ultrathin carbon nitride nanosheets.

[0053] Figure 6 The experimental results of photocatalytic hydrogen production cycle of the single-atom photocatalyst prepared in Example 2 are shown.

[0054] Figure 7 The image shows the photocatalytic hydrogen production effect of the single-atom photocatalyst prepared in this invention under different metal loadings.

[0055] Figure 8 This is an X-ray diffraction (XRD) pattern of the lithium carbonate recovered in this invention. Detailed Implementation

[0056] The present invention will be described in detail below with reference to specific embodiments and examples, thereby making the advantages and various effects of the present invention more clearly apparent. Those skilled in the art should understand that these specific embodiments and examples are for illustrative purposes only and are not intended to limit the present invention.

[0057] Throughout this specification, unless otherwise specified, the terminology used herein should be understood as having the meaning commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the event of any conflict, this specification shall prevail.

[0058] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be obtained by purchasing them from the market or by existing methods.

[0059] Example 1

[0060] A method for preparing single-atom photocatalysts using lithium-ion battery waste as raw material, the process flow diagram is as follows: Figure 1 The details are as follows:

[0061] (1) Battery pretreatment: The recycled waste ternary lithium batteries are dried at 300°C to remove the electrolyte, and then the battery shell and current collector are removed by mechanical crushing and sorting to obtain mixed waste containing positive electrode material and negative electrode material.

[0062] (2) Lithium carbonate recovery: After roasting the mixed waste at 800℃ for 4 hours in a nitrogen atmosphere, water is added at room temperature at a solid-liquid ratio of 50 g / L. The leaching reaction is carried out through water, and carbon dioxide gas is continuously introduced during the leaching process (the flow rate is 60 mL / min per liter of water). After the reaction is carried out for 2 hours, the lithium-containing leachate and nickel-cobalt-manganese-containing waste residue are recovered by filtration. Finally, the lithium carbonate in the leachate is recovered by evaporation crystallization and hot filtration.

[0063] (3) Preparation of single-atom photocatalyst: After washing and drying the nickel-cobalt-manganese waste residue, it was subjected to acid leaching reaction with sulfuric acid solution. The sulfuric acid concentration was 4.0M (M is the abbreviation for mol / L), the solid-liquid ratio was 60g / L, and the reaction was carried out at 80℃ for 3h with rapid stirring. Then, the mixed metal solution containing nickel, cobalt and manganese and solid carbon slag were obtained by filtration. 8g of melamine and 3mL of sulfuric acid (volume fraction 98%) were added to 100mL of water and stirred rapidly at 80℃ for 10min. Then, 0.1mL of the aforementioned mixed metal solution was added and the reaction was continued for 50min to obtain the reaction solution. The reaction solution was transferred to a high-pressure reactor and reacted at 180℃ for 20h. Then, it was filtered, washed three times with deionized water, and dried to obtain a white powder. The white powder was calcined at 550℃ for 4h under a nitrogen atmosphere to obtain a light yellow material, i.e., a single-atom photocatalyst.

[0064] Example 2

[0065] This embodiment is basically the same as Embodiment 1, except that the amount of mixed metal solution added is 0.5 mL.

[0066] Example 3

[0067] This embodiment is basically the same as Embodiment 1, except that the amount of mixed metal solution added is 1.0 mL.

[0068] Example 4

[0069] This embodiment is basically the same as Embodiment 1, except that the amount of mixed metal solution added is 2.0 mL.

[0070] Example 5

[0071] This embodiment is basically the same as Embodiment 1, except that the amount of mixed metal solution added is 4.0 mL.

[0072] Comparative Example 1

[0073] 8g of melamine was calcined at 550°C for 4 hours under a nitrogen atmosphere to obtain a pale yellow material, which was blocky carbon nitride (BCN). This comparative example differs from Example 1 in that no mixed metal solution was added during the material synthesis process; and no acid reaction treatment or hydrothermal reaction treatment was performed.

[0074] Comparative Example 2

[0075] 8g of melamine and 3mL of sulfuric acid were added to 100mL of water and stirred rapidly at 80℃ for 60min to obtain a reaction solution. The reaction solution was transferred to a high-pressure reactor and reacted at 180℃ for 20h. The mixture was then filtered, washed, and dried to obtain a white powder. The white powder was calcined at 550℃ for 4h under a nitrogen atmosphere to obtain a pale yellow material, which is ultrathin carbon nitride nanosheets (UCN). This comparative example differs from Example 1 in that no mixed metal solution was added during the material synthesis process.

[0076] The substances obtained from the examples and comparative examples were tested:

[0077] Figure 2 Aberration-corrected transmission electron microscope image of the single-atom photocatalyst prepared in Example 2; by Figure 2 It can be seen that the prepared material exhibits a two-dimensional ultrathin nanostructure, and the metal is loaded on the surface of the carrier in the form of single atoms.

[0078] Figure 3 The images shown are scanning electron microscope (SEM-EDS) and transmission electron microscope (TEM-EDS) images of the single-atom photocatalyst prepared in Example 2; Figure 3 It can be seen that no nano-metal particles were formed in the prepared material, which is a single-atom catalyst, and the carbon nitride support is an ultrathin nanosheet structure.

[0079] Figure 4 The X-ray diffraction (XRD) patterns of the catalysts prepared in this invention (corresponding to Example 2, Comparative Example 1, and Comparative Example 2); by Figure 4 It can be seen that compared with UCN, the crystallinity of the ultrathin carbon nitride nanosheets (NiCoMn-UCN) decreases, which is due to the increased interlayer spacing. The absorption peak of the nanosheets loaded with single atoms is enhanced and shifted to the right, which confirms that single-atom metals have entered the layers of the material.

[0080] The photocatalytic hydrogen production performance of the catalyst prepared above was tested on a photocatalytic hydrogen production system (Beijing Perfect Light Co., Ltd., Labsolar-6A) coupled with a gas chromatograph (GC9790II, TCD, FULI). High-purity argon was used as the carrier gas in the reaction process. First, 20 mg of the synthesized photocatalyst was dispersed in 100 mL of methanol-water solution (20 wt%), with methanol acting as the electron donor. 1 wt% Pt was precipitated onto the photocatalyst using an H2PtCl6 aqueous solution via in-situ photodeposition as a co-catalyst. In the reaction system, a xenon lamp (Perfect Light PLSSXE300C) equipped with an AM 1.5G filter was used as the light source to simulate sunlight. Vacuuming was performed multiple times before the reaction to remove air. During the reaction, the amount of hydrogen produced was measured periodically using a gas chromatograph. The temperature of the reaction system was maintained at approximately 4°C using circulating cooling water.

[0081] Figure 5 The photocatalytic hydrogen production effect of the catalyst prepared in this invention (corresponding to Example 2, Comparative Example 1, and Comparative Example 2); by Figure 5 It can be seen that the photocatalytic hydrogen production efficiency of the synthesized single-atom supported nanosheet catalyst is significantly improved.

[0082] Figure 6 The experimental results of photocatalytic hydrogen production cycle of the single-atom photocatalyst prepared in Example 2 (corresponding to Example 2); by Figure 6 It can be seen that the efficiency of the synthesized single-atom supported nanosheet catalyst did not decrease after multiple cycles.

[0083] Figure 7 The photocatalytic hydrogen production effect of the single-atom photocatalyst prepared in this invention under different metal loadings (corresponding to Examples 1-5, Comparative Example 2); by Figure 7 It can be seen that the metal loading has a significant impact on the catalytic performance of the catalyst, and it first increases and then decreases with the increase of the loading.

[0084] Figure 8 The X-ray diffraction (XRD) patterns of lithium carbonate recovered in this invention (corresponding to Examples 1-5); by Figure 8 It can be seen that the recovered lithium carbonate and commercially available lithium carbonate have similar absorption peaks and no impurity peaks, indicating that the recovered product has high purity.

[0085] In summary, this invention utilizes waste ternary lithium-ion batteries as raw materials to recover high-value-added lithium carbonate and synthesize a single-atom photocatalyst, significantly improving the performance of the photocatalyst in catalytic hydrogen production. Compared with traditional wet recycling processes, this process prioritizes lithium extraction while using a nickel-cobalt-manganese mixture to synthesize the single-atom catalyst, avoiding complex metal separation processes. Furthermore, this process utilizes the graphite anode from waste batteries as a carbon source, avoiding the use of hydrogen peroxide in traditional processes and greatly reducing production costs. Compared with conventional methods, this invention has advantages such as low cost, simple operation, short process, high economic benefits, and green sustainability, and has significant implications for environmental protection, resource recycling, and social sustainable development.

[0086] Finally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0087] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0088] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing single-atom photocatalysts using lithium-ion battery waste as raw material, characterized in that... Includes the following steps: (1) Pre-treatment of waste batteries: The waste ternary lithium batteries obtained from recycling are dried, crushed and sorted to obtain waste containing positive electrode materials and negative electrode materials; (2) Recovering lithium carbonate: The waste obtained in step (1) is roasted at high temperature under anaerobic conditions. Then, the roasted product is extracted by water leaching to extract lithium. During the water leaching process, CO2 is continuously introduced to promote the dissolution of lithium ions. Then, the leachate containing lithium ions and the waste residue containing nickel, cobalt and manganese are obtained by filtration. The leachate is evaporated, crystallized and filtered to obtain white powdered lithium carbonate. (3) Preparation of single-atom photocatalysts: A. The waste residue containing nickel, cobalt and manganese obtained in step (2) is leached in sulfuric acid solution and filtered to obtain a mixed metal solution containing nickel, cobalt and manganese and carbon slag. B. Melamine, sulfuric acid, water, and the mixed metal solution containing nickel, cobalt, and manganese obtained in step A are mixed and reacted; this reaction partially converts melamine into cyanuric acid, forming a mixture. C. The mixture obtained in step B is subjected to a hydrothermal reaction, and the precipitate is separated from the product; the precipitate is washed and dried to obtain a supramolecular precursor; D. The supramolecular precursor obtained in step C is calcined at high temperature under oxygen-free conditions to obtain a single-atom photocatalyst. The melamine, sulfuric acid, water, and the mixed metal solution containing nickel, cobalt, and manganese obtained in step (3)B shall be mixed in the following ratio: (6-10) g: (1-5) mL: (80-120) mL: (0.1-4.0) mL. The sulfuric acid mentioned in step (3)B is sulfuric acid with a concentration of 98% by volume; The reaction conditions described in step (3)B are: reaction at 60-90℃ for 30-120 min; The hydrothermal reaction conditions described in step (3) C are: reaction at 160–200 °C for 1–24 h; The high-temperature roasting conditions described in step (3) D are roasting at 500-600℃ for 2-6 hours.

2. The method for preparing single-atom photocatalysts using lithium-ion battery waste as raw material according to claim 1, characterized in that: The drying temperature described in step (1) is 250–350°C; The crushing described in step (1) is mechanical crushing; The oxygen-free conditions described in step (2) are obtained by filling the gas with an inert gas; The washing solvent mentioned in step (3)C is deionized water; The number of washes described in step (3) C is 1 to 5; The oxygen-free conditions described in step (3) D are obtained by filling with an inert gas.

3. The method for preparing single-atom photocatalysts using lithium-ion battery waste as raw material according to claim 2, characterized in that: The inert gas is one or both of nitrogen and helium.

4. The method for preparing single-atom photocatalysts using lithium-ion battery waste as raw material according to claim 1, characterized in that: The high-temperature calcination conditions described in step (2) are calcination at 700-850℃ for 1-5 hours; The CO2 flow rate mentioned in step (2) is 30-80 mL / min per liter of water. The amount of water used is calculated as follows: water:waste = 1L: 30-70g. The leaching conditions described in step (2) are a reaction at room temperature for 1 to 3 hours.

5. The method for preparing single-atom photocatalysts using lithium-ion battery waste as raw material according to claim 1, characterized in that: The concentration of the sulfuric acid solution mentioned in step (3)A is 2.0–6.0 mol / L; The amount of sulfuric acid solution used in step (3)A is calculated based on the ratio of waste residue containing nickel, cobalt, and manganese to sulfuric acid solution = 40-80g: 1L; The leaching temperature described in step (3)A is 60–90°C; The leaching time mentioned in step (3)A is 2 to 4 hours.

6. The method for preparing single-atom photocatalysts using lithium-ion battery waste as raw material according to claim 1, characterized in that: Step (3)B is: melamine and sulfuric acid are added to water and mixed to carry out a pre-reaction, and then the mixed metal solution containing nickel, cobalt and manganese obtained in step A is added to continue the reaction.

7. The method for preparing single-atom photocatalysts from lithium-ion battery waste according to claim 6, characterized in that: The pre-reaction conditions are: reaction at 60–90°C for 5–15 minutes; The conditions for continued reaction are 60–90°C for 25–55 min.

8. A single-atom photocatalyst, characterized in that: It is prepared by the method described in any one of claims 1 to 7.

9. The application of the single-atom photocatalyst according to claim 8 in photocatalytic hydrogen production.

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