A koh-loaded molybdenum disulfide photothermal catalyst, a preparation method and application thereof

Abstract

The application discloses a KOH-loaded molybdenum disulfide photothermal catalyst and a preparation method and application thereof, relates to the technical field of photothermal catalytic reduction of CO2, and specifically comprises the following steps: obtaining a homogeneous solution by taking ammonium molybdate tetrahydrate and thiourea as raw materials, obtaining a mixed solution after hydrothermal treatment, performing centrifugal treatment, washing treatment and drying treatment, and then performing one-time calcination treatment to obtain molybdenum disulfide powder, and finally loading KOH to obtain the KOH-loaded molybdenum disulfide photothermal catalyst. The preparation method of the catalyst uses MoS2 with edge coordination unsaturation as a supporting carrier, and through loading of KOH, MoS2 is changed from inert basal plane dominance to high-activity defect structure / alkaline basal plane, the alkaline basal plane makes it easier to adsorb CO2 molecules, form intermediate products, and inhibit the phenomenon that the catalyst is deactivated due to sulfur oxidation loss in the catalytic process. Therefore, the photothermal catalyst has great potential in the reduction of CO2.

Description

Technical Field

[0001] This invention relates to the field of photothermal catalytic reduction of CO2, and more specifically, to a KOH-supported molybdenum disulfide photothermal catalyst, its preparation method, and its application. Background Technology

[0002] With the increasing global energy demand and the growing severity of environmental challenges, developing renewable energy and reducing carbon dioxide (CO2) emissions have become critical global issues. Traditional use of fossil fuels not only leads to greenhouse gas emissions but also causes a series of environmental problems such as global climate change and air pollution. Therefore, finding sustainable energy alternatives and effectively utilizing CO2 has become a research focus in recent years. However, due to the stable structure of CO2, it is difficult to activate and participate in reactions, resulting in limited effectiveness of these methods and failing to solve the fundamental problems. In recent years, research on CO2 conversion technologies has increased significantly, with electrochemical reduction, thermocatalytic conversion, and photothermal catalysis being among the most promising methods. Of these technologies, photothermal catalysis has attracted considerable attention due to its unique advantages. This technology combines light and heat energy, effectively promoting electron transfer and reactant conversion in the catalytic reaction process, thereby achieving a highly efficient CO2 conversion process. It converts the almost limitless solar energy in nature into usable chemical energy, achieving CO2 conversion and utilization without consuming fossil fuels. The core of photothermal catalysis is the selection and design of the catalyst; the performance of the catalyst directly affects the reaction efficiency and product selectivity. Therefore, designing a highly efficient CO2 reduction photothermal catalyst is crucial to achieving this goal.

[0003] Molybdenum disulfide (MoS2) is a widely used metal sulfide in thermocatalysis, frequently applied in hydrogenation and deoxygenation reactions. MoS2 possesses a hexagonal layered structure, with Mo atoms in a fully saturated coordination state between layers. Specifically, each Mo atom is bonded to one of the three nearest sulfur atoms, and each sulfur atom is bonded to one of the six surrounding Mo atoms. These layers are bound together by van der Waals forces. The atoms with fully saturated coordination on the basal planes of MoS2 are chemically inert, while a few edge sites become catalytically active sites due to their unsaturated coordination. Therefore, activating the inert basal planes to enhance the catalytic activity of MoS2 is of great significance. Thus, there is an urgent need to provide a preparation method to improve the activity and selectivity of the catalyst for the photothermal reduction of CO2. Summary of the Invention

[0004] To further improve the photothermal catalytic reduction performance of MoS2 for CO2, this invention provides a KOH-supported MoS2 photothermal catalyst prepared by KOH treatment, its preparation method, and its application in photothermal catalytic reduction of CO2.

[0005] The first aspect of this invention provides a method for preparing a KOH-supported molybdenum disulfide photothermal catalyst, the preparation method specifically comprising the following steps:

[0006] S1. Add ammonium molybdate tetrahydrate and thiourea to deionized water and stir to obtain homogeneous solution A;

[0007] S2. The homogeneous solution A obtained in step S1 is subjected to hydrothermal treatment to obtain mixed solution B;

[0008] S3. After centrifuging the mixed solution B obtained in step S2, the precipitate is washed and dried in sequence, and finally calcined once to obtain molybdenum disulfide powder.

[0009] S4. Add the molybdenum disulfide powder obtained in step S3 to deionized water, then add potassium hydroxide solution dropwise, and stir and dry in sequence to obtain black powder. After a second calcination of the black powder, obtain KOH-supported molybdenum disulfide photothermal catalyst.

[0010] Compared with existing technologies, this invention provides a simple method for preparing a KOH-supported MoS2 photothermal catalyst, enabling the controllable synthesis of MoS2 as a support and KOH anchored on the support. Strong alkaline solution KOH and edge-coordinated unsaturated MoS2 are used as KOH and MoS2, respectively. + Regarding the source of the support, KOH can convert Mo at high temperatures. 6+ Restored to Mo 4+ And prevent Mo 4+ Further oxidation ensures the stability of the active site.

[0011] In one possible implementation, in step S1, the molar ratio of ammonium molybdate tetrahydrate to thiourea is 1:(27-33).

[0012] Compared with existing technologies, this ratio precisely matches the sulfur source supply required to form the ideal MoS2 crystal structure, ensuring that molybdenum atoms are fully sulfidated to build a stable layered framework, while avoiding the formation of impurity phases or unreacted residues due to excessive thiourea. At the same time, this stoichiometric ratio is conducive to the formation of a uniform precursor solution during the hydrothermal process, laying the foundation for obtaining MoS2 nanosheets with high crystallinity, high specific surface area and fully exposed edge active sites, thereby synergistically improving the photothermal responsiveness and sulfur vacancy controllability of the final catalyst.

[0013] In one possible implementation, the specific parameters of the hydrothermal treatment in step S2 are as follows: temperature 200-220 ℃, time 5.5-6.5 h.

[0014] Compared with existing technologies, this temperature and time window synergistically optimizes the crystallinity and microstructure of MoS2—ensuring sufficient hydrothermal reaction kinetics to form a stable layered crystal structure while avoiding nanosheet stacking or structural defects caused by overgrowth; at the same time, it precisely matches the precursor decomposition and self-assembly process, promoting the directional growth of three-dimensional flower-like nanosheets, thereby maximizing the exposure of edge active sites and constructing efficient mass transfer channels, providing an ideal support substrate for subsequent sulfur vacancy construction and photothermal synergistic catalysis.

[0015] In one possible implementation, the centrifugation parameters in step S3 are as follows: rotation speed of 450-600 rpm and time of 20-30 min.

[0016] Compared with existing technologies, this range precisely matches the sedimentation kinetics of molybdenum disulfide nanomaterials—appropriate rotation speed ensures efficient separation of solid-phase precipitates in hydrothermal products, avoiding impurity residues caused by low speed or damage to the nanosheet structure caused by high speed; the simultaneously optimized centrifugation time ensures sufficient phase separation while maximizing the preservation of the open morphology and edge active sites of the three-dimensional flower-like nanosheets, providing a high specific surface area and low aggregation support substrate for subsequent KOH modification, thereby synergistically improving the sulfur vacancy formation efficiency and catalytic activity stability.

[0017] In one possible implementation, the drying parameters in step S3 are as follows: temperature 50-70℃, time 10-13 h.

[0018] Compared with the prior art, the present invention uses the above-mentioned drying parameters. The temperature and appropriate duration work together to ensure the physicochemical stability of the molybdenum disulfide nanostructure. The low temperature range (50-70℃) effectively removes residual solvent (water / ethanol) and avoids sulfur loss or nanosheet oxidation caused by high temperature. The simultaneously optimized drying time (10-13h) ensures sufficient dehydration while maximally suppressing the agglomeration or microcracks caused by rapid shrinkage of the nanosheets. This maintains the open pore structure and edge active site integrity of the high specific surface area carrier substrate, providing an ideal active site substrate for the efficient construction of sulfur vacancies and photothermal catalytic interfacial reaction in subsequent KOH modification.

[0019] In one possible implementation, in step S3, the primary calcination treatment is carried out in a tubular furnace, and the parameters of the primary calcination treatment are as follows: the temperature is raised to 200-400 ℃ at a heating rate of 5-10 ℃ / min for 2-2.5 h, and nitrogen gas is continuously introduced during the calcination treatment.

[0020] Compared with existing technologies, this gradient temperature and precise duration synergistically optimize the lattice activation and defect control of MoS2—the low-temperature region (from 200 °C) effectively removes residual impurities and avoids high-temperature sulfur loss, while the high-temperature end (up to 400 °C) fully activates basal atomic bonds without destroying the layered framework; simultaneous introduction of nitrogen creates an oxygen-deficient environment, precisely suppressing sulfur oxidation and stabilizing Mo. 4+ The valence state is determined to construct high concentrations of sulfur vacancies while maintaining the integrity of the edge unsaturated coordination structure. At the same time, the appropriate calcination time (2-2.5 h) under nitrogen atmosphere ensures that the crystal reconstruction is fully completed, laying a low defect energy barrier support for the subsequent KOH insertion into the interlayer to expand the active interface (K-Mo-S structure), and ultimately synergistically improving the electron transfer efficiency and CO2 reduction stability of the photothermal catalyst.

[0021] In one possible implementation, in step S4, the mass ratio of potassium hydroxide in the potassium hydroxide solution to the mass of molybdenum disulfide powder is (0.08-0.12):1.

[0022] Compared with existing technologies, the advantages of using potassium hydroxide in this invention are:

[0023] 1. The strong alkalinity of KOH promotes the activation of CO2. CO2 is an acidic gas, and strong bases (such as KOH) interact with it more readily: CO2 chemisorption is enhanced. KOH provides OH- - It can react directly with CO2 to produce carbonates (such as potassium carbonate) or formates (HCOO). - This lowers the energy barrier for CO2 activation. Other potassium salts (such as KCl and KNO3) lack strongly basic sites and have a weaker ability to adsorb CO2. It also promotes the breaking of C=O bonds. In hydrogenation reactions (such as the reduction of CO2 to CO or CH4), the basic sites of KOH can polarize the C=O bonds, making them easier to break.

[0024] 2. Synergistic effect of KOH and MoS2: MoS2 is a typical transition metal sulfide, and its catalytic performance depends on the edge Mo-S active sites. The introduction of KOH can optimize these sites and regulate the electronic structure of MoS2: K + The electron donor effect can increase the electron density of the conduction band of MoS2, promoting the reduction of CO2 (e.g., CO2 + e-). - →CO2 - Other potassium salts (such as K2SO4) cannot effectively modulate the electronic properties of MoS2.

[0025] 3. Formation of sulfur vacancies: During high-temperature treatment, KOH reacts with sulfur atoms on the surface of MoS2 to generate K2S, leaving sulfur vacancies. These vacancies are key sites for CO2 adsorption and activation. Neutral potassium salts (such as KCl) are unlikely to induce the formation of sulfur vacancies.

[0026] 4. Decomposition of potassium salts and high-temperature decomposition of KOH formed by the active phase: Under the reaction conditions, KOH partially decomposes into K₂O or K₂O. + These species interact with MoS2 to form highly active interfaces (such as K-Mo-OS structures). However, salts such as potassium carbonate have high decomposition temperatures, making it difficult to release active components under mild conditions.

[0027] In one possible implementation, in step S4, the secondary calcination treatment is carried out in a tube furnace, and the parameters of the secondary calcination treatment are as follows: the temperature is raised to 250-350 ℃ at a heating rate of 5-10 ℃ / min for 2-2.5 h, and the atmosphere is nitrogen.

[0028] The second objective of this invention is to provide a KOH-supported molybdenum disulfide photothermal catalyst, prepared by the above-described method.

[0029] Compared with existing technologies, this invention constructs a highly efficient insoluble catalyst applicable to the photothermal catalytic reduction of CO2 by loading KOH to adjust the atomic configuration. This transforms MoS2 from an inert basal plane-dominated structure to a highly active defect structure. Specifically, after loading KOH, a K-Mo-S mixed interface structure is formed, where K... + Insertion of molybdenum disulfide into the interlayer space increases the interlayer spacing, and the embedded K + It can compensate for the negative charge of sulfur vacancies, reduce the defect formation energy, and promote the formation of more sulfur vacancies. In the K-Mo-S structure, K + In synergy with sulfur vacancies, this catalyst optimizes CO2 adsorption and activation and promotes the adsorption and conversion of intermediate carboxyl groups and carbon monoxide, surpassing edge-coordinated unsaturated MoS2 in selectivity and activity during photothermal catalytic CO2 reduction. Compared to MoS2, in this catalyst, the loading of KOH increases sulfur vacancy formation without affecting the original edge-coordinated unsaturated state.

[0030] The third objective of this invention is to provide the application of the KOH-supported molybdenum disulfide photothermal catalyst in the field of photocatalytic CO2 reduction.

[0031] Compared with existing technologies, the preparation method of this invention uses MoS2 as a support and adds KOH during the synthesis process to construct a photothermal catalyst with an alkaline basal surface, which makes it easier to adsorb CO2 molecules and form the intermediate product (HCO3). -This effectively improves reduction efficiency. MoS2 inherently possesses advantages such as multi-electron transfer capability, excellent light and heat absorption, and unsaturated coordination at its edges. Furthermore, loading with KOH increases the interlayer spacing of MoS2, reducing stacking layers and exposing more active sites. It also suppresses catalyst deactivation due to sulfur oxidation during catalysis. Therefore, KOH-supported MoS2 photothermal catalysts have great potential for CO2 reduction. Attached Figure Description

[0032] Figure 1 X-ray diffraction comparison patterns of 10% KOH-MoS2 prepared in Example 1 and MoS2 prepared in Comparative Example 1;

[0033] Figure 2 Scanning electron microscope (SEM) images of 10% KOH-MoS2 prepared in Example 1 and MoS2 prepared in Comparative Example 1.

[0034] Figure 3 X-ray photoelectron spectra of 10% KOH-MoS2 prepared in Example 1 and MoS2 prepared in Comparative Example 1;

[0035] Figure 4 Comparative graphs show the performance of photothermal catalysts prepared in Comparative Example 1 (Material A), Example 1 (Material B), Comparative Example 2 (Material C), Comparative Example 3 (Material D), and Comparative Example 4 (Material E).

[0036] Figure 5 The performance comparison charts show the photothermal catalysts prepared in Example 1 (Material B), Comparative Example 5 (Material F), Comparative Example 6 (Material G), Comparative Example 7 (Material H), Comparative Example 8 (Material I), and Comparative Example 9 (Material J). Detailed Implementation

[0037] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the claims of the present invention.

[0038] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0039] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some instances, terms having a conventional meaning are defined herein for clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments shall be performed according to the manufacturer's instructions and parameters.

[0040] In this invention, the photothermal reduction of CO2 is carried out in a micro-photothermal catalytic microreactor system (Beijing Zhongjiao Jinyuan CEL-GPPCM). A 300W xenon lamp (PLS-SXE300+) is used as the light source, and the product is detected by Agilent online gas chromatography for gas analysis.

[0041] Gas chromatography analysis conditions: The Agilent GC-8860 online analytical gas chromatograph is equipped with a flame ionization detector (FID) and a thermal conductivity detector (TCD) to detect the CH4 and CO generated in the reaction.

[0042] It is worth mentioning that in the following embodiments, since the CO2 reduction process mainly generates two products, CO and CH4, and because the generation of CH4 and CO is in fierce competition, resulting in reduced selectivity, the target product is CO.

[0043] This invention provides a KOH-supported molybdenum disulfide photothermal catalyst, its preparation method, and its application. The preparation method of the molybdenum disulfide photothermal catalyst specifically includes the following steps:

[0044] S1. Add ammonium molybdate tetrahydrate and thiourea to deionized water and stir to obtain homogeneous solution A. The molar ratio of ammonium molybdate tetrahydrate to thiourea is 1:(27-33). The stirring can be magnetic stirring for about 20-30 minutes.

[0045] S2. The homogeneous solution A obtained in step S1 is subjected to hydrothermal treatment to obtain mixed solution B. The specific parameters of the hydrothermal treatment are as follows: temperature is 200-220 ℃, and time is 5.5-6.5 h.

[0046] S3. After centrifuging the mixed solution B obtained in step S2, the precipitate is washed and dried sequentially, and finally calcined once to obtain molybdenum disulfide powder. The centrifugation parameters are as follows: rotation speed 450-600 rpm, time 20-30 min; the drying parameters are as follows: temperature 50-70 ℃, time 10-13 h; the first calcination is carried out in a tube furnace, and the parameters of the first calcination are as follows: heating to 200-400 ℃ at a heating rate of 5-10 ℃ / min, time 2-2.5 h, and nitrogen gas is continuously introduced during the calcination process.

[0047] S4. Add the molybdenum disulfide powder obtained in step S3 to deionized water, and then add potassium hydroxide solution dropwise. The mass ratio of potassium hydroxide to molybdenum disulfide powder in the potassium hydroxide solution is (0.08-0.12):1. Then, stir and dry the mixture to obtain a black powder. The black powder is then subjected to a second calcination treatment to obtain a KOH-supported molybdenum disulfide photothermal catalyst. The second calcination treatment is carried out in a tube furnace, and the parameters of the second calcination treatment are as follows: the temperature is increased to 250-350 ℃ at a heating rate of 5-10 ℃ / min for 2-2.5 h, and the atmosphere is nitrogen.

[0048] In the specific preparation process, the washing process in step S3 is as follows: the product is washed sequentially with deionized water and 95% ethanol solution, and the washing is performed at least 3 times.

[0049] In step S4, the drying parameters can be the same as in step S3, i.e., the temperature is 50-70℃ and the time is 10-13h.

[0050] The KOH-supported molybdenum disulfide photothermal catalyst prepared by this invention can be used in the field of photocatalytic CO2 reduction.

[0051] Example 1

[0052] This embodiment provides a KOH-supported molybdenum disulfide photothermal catalyst, which is prepared by the following method:

[0053] S1. Add 0.83 g ammonium molybdate tetrahydrate and 1.52 g thiourea to 24 ml of deionized water and stir magnetically for 30 min to form a homogeneous solution, thus obtaining solution A;

[0054] S2. Pour the solution A obtained in step S1 into a 50 ml reaction vessel and hydrothermally heat it at 210 ℃ for 6 h to obtain a mixed solution B.

[0055] S3. Centrifuge mixture B at 450 rpm for 20 min. Wash the resulting black precipitate three times with deionized water and 95% ethanol, then dry it at 60 °C for 12 h. Grind the dried sample into a black powder. Take 200 mg of the black powder and centrifuge at 5 °C / min under a N2 atmosphere. -1 The temperature was heated to 300 °C at a certain rate and calcined at this high temperature for 2 hours. After cooling to room temperature, black powder MoS2 was obtained.

[0056] S4. Take 100 mg of the black powder MoS2 obtained in step S3 and disperse it in 10 ml of deionized water. Stir magnetically until evenly dispersed, then add 5 ml of potassium hydroxide solution (0.002 g·ml). -1 After magnetic stirring for 10 min, it was then heated at 60℃ at 600 r·min. -1 Stirring and drying at a certain rate, collect the dried black powder A; then, under a N2 atmosphere, stir at 5℃·min. -1 The solution was heated to 300°C at a certain rate and calcined at this high temperature for 2 hours. After cooling to room temperature, a black powder was obtained, named 10%KOH-MoS2, and labeled as material B.

[0057] Example 2

[0058] This embodiment provides a KOH-supported molybdenum disulfide photothermal catalyst, which is prepared by the following method:

[0059] S1. Add 0.83 g of ammonium molybdate tetrahydrate and 1.68 g of thiourea to 24 ml of deionized water and stir magnetically for 20 min to form a homogeneous solution, thus obtaining solution A;

[0060] S2. Pour the solution A obtained in step S1 into a 50 ml reaction vessel and hydrothermally heat it at 200 ℃ for 5.5 h to obtain a mixed solution B.

[0061] S3. Centrifuge mixture B at 500 rpm for 25 min. Wash the resulting black precipitate three times with deionized water and 95% ethanol, then dry it at 50℃ for 13 h. Grind the dried sample into a black powder. Take 200 mg of the black powder and centrifuge it at 8℃·min under a N2 atmosphere. -1 The solution was heated to 200 °C at a certain rate and calcined at this high temperature for 2.2 h. After cooling to room temperature, a black powder MoS2 was obtained.

[0062] S4. Take 100 mg of the black powder MoS2 obtained in step S3 and disperse it in 10 ml of deionized water. Stir magnetically until evenly dispersed, then add 6 ml of potassium hydroxide solution (0.002 g·ml). -1After magnetic stirring for 10 min, the mixture was then heated at 50°C at 600 r·min. -1 Stirring and drying at a certain rate, collect the dried black powder A; then, under a N2 atmosphere, stir at 8℃·min. -1 The solution was heated to 250°C at a certain rate and calcined at this high temperature for 2 hours. After cooling to room temperature, a black powder was obtained.

[0063] Example 3

[0064] This embodiment provides a KOH-supported molybdenum disulfide photothermal catalyst, which is prepared by the following method:

[0065] S1. Add 0.83 g of ammonium molybdate tetrahydrate and 1.52 g of thiourea to 24 ml of deionized water and stir magnetically for 25 min to form a homogeneous solution, thus obtaining solution A;

[0066] S2. Pour the solution A obtained in step S1 into a 50 ml reaction vessel and hydrothermally heat it at 220 ℃ for 6.5 h to obtain a mixed solution B.

[0067] S3. Centrifuge mixture B at 600 rpm for 30 min. Wash the resulting black precipitate three times with deionized water and 95% ethanol, then dry it at 70 °C for 10 h. Grind the dried sample into a black powder. Take 200 mg of the black powder and centrifuge it at 10 °C / min under a N2 atmosphere. -1 The mixture was heated to 400 °C at a certain rate and calcined at this high temperature for 2.5 h. After cooling to room temperature, a black powder MoS2 was obtained.

[0068] S4. Take 100 mg of the black powder MoS2 obtained in step S3 and disperse it in 10 ml of deionized water. Stir magnetically until evenly dispersed, then add 4 ml of potassium hydroxide solution (0.002 g·ml). -1 After magnetic stirring for 10 min, the mixture was then heated at 50°C at 600 r·min. -1 The mixture was stirred and dried at a rate of [missing information], and the dried black powder A was collected. Black powder A was then subjected to [missing information] ℃·min under a N2 atmosphere. -1 The solution was heated to 350 °C at a certain rate and calcined at this high temperature for 2.5 h. After cooling to room temperature, a black powder was obtained.

[0069] Comparative Example 1

[0070] This comparative example provides a molybdenum disulfide photocatalyst, which differs from Example 1 only in that step S4 is omitted in this comparative example. The specific preparation steps are as follows:

[0071] S1. Add 0.83 g ammonium molybdate tetrahydrate and 1.52 g thiourea to 24 ml of deionized water and stir magnetically for 30 min to form a homogeneous solution, thus obtaining solution A;

[0072] S2. Pour the solution A obtained in step S1 into a 50 ml reaction vessel and hydrothermally heat it at 210 ℃ for 6 h to obtain a mixed solution B.

[0073] S3. Centrifuge mixture B at 450 rpm for 20 min. Wash the resulting black precipitate three times with deionized water and 95% ethanol, then dry it at 60 °C for 12 h. Grind the dried sample into a black powder. Take 200 mg of the black powder and centrifuge at 5 °C / min under a N2 atmosphere. -1 The mixture was heated to 300 °C at a certain rate and calcined at this high temperature for 2 hours. After cooling to room temperature, a black powder, MoS2, was obtained and labeled as material A.

[0074] Comparative Example 2

[0075] This comparative example provides a KOH-supported molybdenum disulfide photothermal catalyst, labeled as material C. The only difference from Example 1 is that in step S4 of this comparative example, the mass of KOH is 2 mg. The rest is the same as in Example 1 and will not be repeated here.

[0076] Comparative Example 3

[0077] This comparative example provides a KOH-supported molybdenum disulfide photothermal catalyst, labeled as material D. The only difference from Example 1 is that in step S4 of this comparative example, the mass of KOH is 5 mg. The rest is the same as in Example 1 and will not be repeated here.

[0078] Comparative Example 4

[0079] This comparative example provides a KOH-supported molybdenum disulfide photothermal catalyst, labeled as Material E. The only difference from Example 1 is that in step S4 of this comparative example, the mass of KOH is 15 mg. The rest is the same as in Example 1 and will not be repeated here.

[0080] Comparative Example 5

[0081] This comparative example provides a KOH-supported molybdenum disulfide photothermal catalyst, labeled as material F. The only difference from Example 1 is that in step S4 of this comparative example, the calcination temperature is 500 °C. The rest is the same as in Example 1, and will not be repeated here.

[0082] Comparative Example 6

[0083] This comparative example provides a KOH-supported molybdenum disulfide photothermal catalyst, labeled as material G. The only difference from Example 1 is that the calcination temperature in step S4 of this comparative example is 400 °C. The rest is the same as in Example 1 and will not be repeated here.

[0084] Comparative Example 7

[0085] This comparative example provides a KOH-supported molybdenum disulfide photothermal catalyst, labeled as material H. The only difference from Example 1 is that the calcination temperature in step S4 of this comparative example is 380 °C. The rest is the same as in Example 1 and will not be repeated here.

[0086] Comparative Example 8

[0087] This comparative example provides a KOH-supported molybdenum disulfide photothermal catalyst, labeled as Material I. The only difference from Example 1 is that the calcination temperature in step S4 of this comparative example is 230 °C. The rest is the same as in Example 1 and will not be repeated here.

[0088] Comparative Example 9

[0089] This comparative example provides a KOH-supported molybdenum disulfide photothermal catalyst, labeled as material J. The only difference from Example 1 is that in step S4 of this comparative example, the calcination temperature is 200 °C. The rest is the same as in Example 1 and will not be repeated here.

[0090] Performance testing:

[0091] The materials obtained in Example 1 and Comparative Example 1 were subjected to photothermal catalytic reduction of CO2 under visible light irradiation. The specific implementation steps are as follows:

[0092] The entire reaction is carried out in a gas-solid reaction system. In a typical procedure, 0.2 g of quartz sand is packed into a quartz glass tube, followed by 20 mg of prepared material B or material A. The quartz tube is then fixed in the reaction apparatus, and argon gas is introduced until the pressure reaches 100 kPa. This pressure is maintained for 10-15 min, after which the pressure is released. A mixture of CO2 and H2 is introduced, and the xenon lamp is turned on. The products CO and CH4 are detected hourly using an online gas chromatograph.

[0093] This invention uses MoS2 as a precursor to explore the photothermal catalytic performance of KOH with different loading contents, in order to obtain the optimal photothermal catalytic performance of CO2.

[0094] Figure 1The X-ray diffraction (XRD) patterns of 10% KOH-MoS2 prepared in Example 1 and MoS2 prepared in Comparative Example 1 are shown in comparison. The results indicate that the XRD characteristic peak positions of 10% KOH-MoS2 prepared in Example 1 remain essentially unchanged, indicating that the KOH-supported catalyst can still maintain a good crystal structure. Furthermore, the characteristic peak intensity of the KOH-supported catalyst is higher than that of the pure MoS2 catalyst, suggesting that the 10% KOH-MoS2 prepared in Example 1 is beneficial for the enrichment of active sites due to the edge effect. In addition, the diffraction peaks of the (002) plane of MoS2 prepared in Comparative Example 1 and 10% KOH-MoS2 prepared in Example 1 show slight shifts, which may be due to the KOH-supported catalyst. + The defects are caused by lattice distortion resulting from the replacement of some atoms in MoS2 or their entry into interstitial sites, indicating the presence of defects on the inert basal surface.

[0095] Figure 2 The images show scanning electron microscope (SEM) images of 10% KOH-MoS2 prepared in Example 1 and MoS2 prepared in Comparative Example 1, where (a) is an SEM image of MoS2 prepared in Comparative Example 1 and (b) is an SEM image of 10% KOH-MoS2 prepared in Example 1; from Figure 2 As can be seen from the scanning electron microscope images of the MoS2 catalyst before and after KOH loading, it exhibits a three-dimensional flower-like nanosheet structure. These nanosheets are interconnected, forming a three-dimensional flower-like network. This network overcomes the disordered stacking of the MoS2 layers by exposing numerous active edge sites and increasing the specific surface area, thereby reducing the diffusion pathways of reactants and surface charges.

[0096] Figure 3 X-ray photoelectron spectroscopy (XPS) of 10% KOH-MoS2 prepared in Example 1 and MoS2 prepared in Comparative Example 1 are shown. All representative spectra of Mo 3d and S 2s after calibration at the standard C 1s peak at 284.6 eV are displayed. The fitting criteria included three aspects: (a) the spin-orbit splitting energy is fixed; (b) each peak corresponds to the full width at half maximum (FWHM); and (c) the peak area ratio of each doublet is determined according to the spin-state degeneracy. Based on these fitting criteria, the elemental coordination structure of MoS2 is clearly described.

[0097] Mo 3d 5 / 2 and Mo 3d 3 / 2 The two characteristic peaks at 229.7 and 232.8 eV represent Mo. 4+ Tiny Mo atoms were observed at 233.0 and 236.0 eV. 6+ Peak. Mo after KOH loading modification 4+The peak positions shift towards lower binding energies, at 229.4 and 232.3 eV, respectively. This indicates that the number of S vacancies on the catalyst surface increases after KOH loading. The S 2p vacancies at 162.6 and 163.7 eV are attributed to unsaturated S. 2- or terminal S2 2- S 2p 3 / 2 and S 2p 1 / 2 The orbitals, after being loaded with KOH, shift towards lower binding energies, reaching 162.0 and 163.2 eV. This indicates that a portion of the S... 2- and S2 2- The S-vacancy is formed by moving it out from the inert basal surface.

[0098] Figure 4 This is a performance comparison chart of the photothermal catalysts prepared in Comparative Example 1 (Material A), Example 1 (Material B), Comparative Example 2 (Material C), Comparative Example 3 (Material D), and Comparative Example 4 (Material E). Figure 4 It can be seen that the CO evolution rate in the photothermal catalytic CO2 reduction reaction of the 10% KOH-MoS2 catalyst prepared in Example 1 of this invention is 4.25 mmol g. -1 h -1 The selectivity was as high as 99.8%, far exceeding the activity and selectivity of pure MoS2 photothermal catalytic CO2 reduction (0.59 mmol g). -1 h -1 (and 96.3%). This further illustrates that the 10% KOH-MoS2 photothermal catalyst prepared using the preparation parameters of this invention can achieve highly efficient photocatalytic CO2 reduction.

[0099] Figure 5 This is a performance comparison chart of the photothermal catalysts prepared in Example 1 (Material B), Comparative Example 5 (Material F), Comparative Example 6 (Material G), Comparative Example 7 (Material H), Comparative Example 8 (Material I), and Comparative Example 9 (Material J). Figure 5 It can be seen that the CO evolution rate in the photothermal catalytic CO2 reduction reaction of the 10% KOH-MoS2 catalyst prepared in Example 1 of this invention is 4.25 mmol g. -1 h -1 The selectivity reached 99.8%, exceeding the catalytic activity of 10% KOH-MoS2 photothermal catalysts prepared at other calcination temperatures (the highest performance of others was 4.11 mmol g). -1 h -1 (and 98.3% selectivity).

[0100] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing a KOH-supported molybdenum disulfide photothermal catalyst, characterized in that, Specifically, the steps include the following: S1. Add 0.83 g ammonium molybdate tetrahydrate and 1.52 g thiourea to 24 ml of deionized water and stir magnetically for 30 min to form a homogeneous solution, thus obtaining solution A; S2. Pour the solution A obtained in step S1 into a 50 ml reaction vessel and hydrothermally heat it at 210 ℃ for 6 h to obtain a mixed solution B. S3. Centrifuge mixture B at 450 rpm for 20 min. Wash the resulting black precipitate three times with deionized water and 95% ethanol, then dry it at 60 °C for 12 h. Grind the dried sample into a black powder. Take 200 mg of the black powder and centrifuge at 5 °C / min under a N2 atmosphere. -1 The temperature was heated to 300 °C at a certain rate and calcined at this high temperature for 2 hours. After cooling to room temperature, black powder MoS2 was obtained. S4. Take 100 mg of the black powder MoS2 obtained in step S3, disperse it in 10 ml of deionized water, stir magnetically until evenly dispersed, and add dropwise 5 ml of water containing 0.002 g·ml⁻¹. -1 A potassium hydroxide solution was prepared, magnetically stirred for 10 min, and then heated at 60°C at 600 r·min. -1 Stirring and drying at a certain rate, collect the dried black powder A; then, under a N2 atmosphere, stir at 5℃·min. -1 The solution is heated to 300°C at a certain rate and calcined at this high temperature for 2 hours, then cooled to room temperature to obtain the final product.

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