An Ag2S / Cd 0.5 Zn 0.5 S photocatalytic material, preparation method and application thereof

Abstract

The application provides an Ag2S / Cd 0.5 Zn 0.5 The application relates to a S-type photocatalytic material, a preparation method and application thereof, and belongs to the technical field of photocatalytic decomposition of water to produce hydrogen. In view of the problems of serious photocarrier recombination and photo-corrosion of a Cd0.5Zn0.5S solid solution photocatalytic material, CZS nanorods with different crystallinity and sulfur vacancy concentration are prepared by a hydrothermal method by adjusting a synthesis temperature, and S-type heterojunction is constructed by loading Ag2S nanoparticles. The built-in electric field formed between Ag2S and CZS is designed to drive the photo-generated electrons to follow the S-type transfer path, efficient spatial separation of the photocarriers is realized, and the strong oxidation-reduction capacity of the system is reserved. The synergistic strategy significantly improves the visible light response and structural stability, and provides a feasible idea for interface engineering design of sulfide-based photocatalytic materials.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic water splitting for hydrogen production, and particularly to an Ag2S / Cd... 0.5 Zn 0.5 S photocatalytic materials, their preparation methods, and applications. Background Technology

[0002] Solar-driven photocatalytic water splitting for hydrogen production is an ideal way to directly convert clean and renewable solar energy into high-energy-density chemical energy (hydrogen energy). Due to its abundant resources, environmentally friendly reaction process, and huge energy conversion potential, it is widely regarded by the academic community as a core component of the future clean energy system. The core key to photocatalytic water splitting for hydrogen production lies in the design and development of high-performance photocatalysts. Since Fujishima and Honda first discovered water splitting on TiO2 photoelectrodes in 1972, researchers worldwide have conducted extensive research on optimizing the performance of photocatalysts, studying various types of semiconductor materials such as oxides, sulfides, and nitrides. Among them, metal sulfides have attracted much attention in the field of photocatalytic hydrogen evolution due to their suitable bandgap, excellent visible light response characteristics, and unique electronic structure. Cd, in particular, has been a key component in this field. 0.5 Zn 0.5 S(CZS) solid solutions combine the excellent visible light absorption of CdS with the high conduction band position (stronger reducing power) of ZnS, showing broad application prospects in the field of photocatalytic hydrogen evolution. However, single CZS materials still face two major bottlenecks: first, photogenerated electron-hole pairs recombine easily, leading to low quantum efficiency; second, under long-term illumination, sulfur ions are easily oxidized by photogenerated holes, causing photocorrosion and poor stability. Therefore, how to suppress carrier recombination and improve material stability is the core scientific problem for promoting the practical application of CZS, and also a current research hotspot and challenge in the field of photocatalysis. Introducing co-catalysts is one of the effective strategies to improve the above problems.

[0003] Ag₂S, as a narrow bandgap semiconductor (approximately 1.0 eV), possesses unique physicochemical properties, offering an ideal solution to the aforementioned problems. It exhibits broad-spectrum absorption characteristics in the visible to near-infrared region, enabling full utilization of solar energy resources. Simultaneously, Ag₂S possesses excellent electron-accepting capabilities, effectively capturing photogenerated electrons. Research shows that combining Ag₂S with CZS can form an S-scheme heterojunction. Under illumination, photogenerated electrons in the Ag₂S conduction band migrate to the CZS valence band, recombine with photogenerated holes in the CZS valence band, while the strongly oxidizing holes retained in the CZS valence band and the strongly reducing electrons retained in the Ag₂S conduction band participate in oxidation and reduction reactions, respectively. This charge transfer pathway not only effectively separates charge carriers but also avoids the loss of redox capabilities. However, according to the formation rules of S-scheme heterojunctions, the crystallinity, defect states, and band structure of the carrier have a decisive influence on the charge transfer efficiency at the heterojunction interface. Summary of the Invention

[0004] The purpose of this invention is to provide an Ag2S / Cd 0.5 Zn 0.5 S photocatalytic materials, their preparation methods, and applications are used to solve the above-mentioned technical problems.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides an Ag2S / Cd 0.5 Zn 0.5 The preparation method of S photocatalytic material includes the following steps: Step 1) Zinc source, cadmium source, sulfur source and ethylenediamine aqueous solution are mixed according to stoichiometric ratio to obtain a mixed solution. The obtained mixed solution is transferred to a reaction vessel and heated for reaction. After natural cooling, the obtained product is centrifuged, washed, and finally dried to obtain Cd. 0.5 Zn 0.5 S powder; Step 2) Dissolve the silver source and sulfur source in solvents according to the stoichiometric ratio of Ag2S. Mix the two solutions and react them. Then wash, centrifuge and dry them in sequence to obtain Ag2S nanoparticles. Step 3) Add Cd 0.5 Zn 0.5 S powder and Ag2S nanoparticles were mixed evenly in a solvent, stirred, and then subjected to a hydrothermal reaction. After the reaction was completed, the mixture was allowed to cool naturally, and then washed and dried sequentially to obtain Ag2S / Cd. 0.5 Zn 0.5 S photocatalytic materials; The Ag2S / Cd 0.5 Zn 0.5In S photocatalytic materials, Ag2S and Cd 0.5 Zn 0.5 The mass ratio of S is 0.03~0.1:1.

[0006] Furthermore, in step 1), the mixing is carried out under stirring conditions for 2-3 hours; The heating temperature is 150~250℃, and the heating time is 20~25h; The drying temperature is 50~80℃, and the drying time is 10~15h.

[0007] Furthermore, in step 1), the cadmium source includes one or more of cadmium acetate, cadmium nitrate, and cadmium chloride; the zinc source includes one or more of zinc acetate, zinc nitrate, and zinc chloride; and the sulfur source includes one or more of thiourea, thioacetamide, and sodium sulfide.

[0008] Furthermore, in step 2), the silver source includes one or more of silver nitrate, silver acetate, and silver ammonia complexes; the sulfur source includes one or more of sodium sulfide, thioacetamide, thiourea, and sodium hydrosulfide. The mixing is carried out under stirring conditions for 5 to 20 minutes; The drying process is carried out under light-protected conditions for 10-15 hours.

[0009] Furthermore, in step 3), the mixing is carried out under stirring conditions for 2-3 hours; The hydrothermal reaction is carried out at a temperature of 100-150℃ for 2-5 hours.

[0010] Furthermore, in step 3), the drying temperature is 50~80℃ and the drying time is 10~15h.

[0011] This invention provides an Ag2S / Cd prepared by the above preparation method. 0.5 Zn 0.5 S photocatalytic materials.

[0012] The present invention also provides the above-mentioned Ag2S / Cd 0.5 Zn 0.5 Application of S photocatalytic materials in photocatalytic hydrogen evolution.

[0013] The beneficial effects of this invention are: This invention utilizes a hydrothermal method to prepare CZS nanorods with different structures at 170 °C and 220 °C, respectively, and then loads Ag₂S nanoparticles onto their surfaces, successfully constructing an Ag₂S / CZS heterojunction photocatalytic system. The effects of hydrothermal temperature on the crystallinity, dispersibility, and sulfur vacancy concentration of the CZS support were systematically investigated, elucidating the intrinsic relationship between temperature, defects, and activity. The results show that the CZS synthesized at 220 °C exhibits higher crystallinity and more sulfur vacancies, making it a superior substrate material for photocatalytic hydrogen evolution in this invention. Under visible light, this system, using Na₂S / Na₂SO₃ as a sacrificial agent, achieves highly efficient photocatalytic hydrogen evolution performance. Various characterization techniques were used to systematically study the crystal structure, surface chemical state, microstructure, optical properties, and band structure of the material. This study focused on investigating the photocatalytic hydrogen evolution performance of Ag₂S / CZS composite catalysts at different hydrothermal temperatures, revealing the microscopic mechanism by which the built-in electric field at the S-type heterojunction interface drives the migration and recombination of photogenerated electrons from the Ag₂S conduction band to the CZS valence band. This synergistic mechanism significantly promotes the spatial separation of photogenerated carriers, greatly enhancing the photocatalytic hydrogen evolution performance. Attached Figure Description

[0014] Figure 1 The images show the morphology and microstructure of the obtained samples, including: (a) TEM image of CZS at 220℃; (b) TEM image of Ag2S; (c) TEM image of 5%Ag2S / CZS at 220℃; (d) HRTEM image of CZS at 220℃; (e) HRTEM image of Ag2S; (f) HRTEM image of 5%Ag2S / CZS at 220℃; and (gj) HAADF-STEM pattern of 5%Ag2S / CZS at 220℃, where (g) Zn, (h) Cd, (i) S, and (j) Ag. Figure 2 The nitrogen adsorption-desorption isotherms and related pore size distributions of the obtained samples are shown, where (a) 170℃ CZS, (b) 170℃ 5%Ag2S / CZS, (c) 220℃ CZS and (d) 220℃ 5%Ag2S / CZS. Figure 3 (a) TPCD curves and (b) EIS Nyquist plots for samples CZS at 170℃, 5%Ag2S / CZS at 170℃, CZS at 220℃, 5%Ag2S / CZS at 220℃, and Ag2S. Figure 4 The visible light hydrogen evolution rate characterization diagrams for CZS, Ag2S, 3%Ag2S / CZS, 5%Ag2S / CZS and 7%Ag2S / CZS at different temperatures are shown, where (a) 220℃ and (b) 170℃. Figure 5The hydrogen evolution activity characterization diagram of 5% Ag2S / CZS at 220℃ in different sacrificial agents obtained in Example 1 is shown. Detailed Implementation

[0015] This invention provides an Ag2S / Cd 0.5 Zn 0.5 The preparation method of S photocatalytic material includes the following steps: Step 1) Zinc source, cadmium source, sulfur source and ethylenediamine aqueous solution are mixed according to stoichiometric ratio to obtain a mixed solution. The obtained mixed solution is transferred to a reaction vessel and heated for reaction. After natural cooling, the obtained product is centrifuged, washed, and finally dried to obtain Cd. 0.5 Zn 0.5 S powder; Step 2) Dissolve the silver source and sulfur source in solvents according to the stoichiometric ratio of Ag2S. Mix the two solutions and react them. Then wash, centrifuge and dry them in sequence to obtain Ag2S nanoparticles. Step 3) Add Cd 0.5 Zn 0.5 S powder and Ag2S nanoparticles were mixed evenly in a solvent, stirred, and then subjected to a hydrothermal reaction. After the reaction was completed, the mixture was allowed to cool naturally, and then washed and dried sequentially to obtain Ag2S / Cd. 0.5 Zn 0.5 S photocatalytic materials; The Ag2S / Cd 0.5 Zn 0.5 In S photocatalytic materials, Ag2S and Cd 0.5 Zn 0.5 The mass ratio of S is 0.03~0.1:1.

[0016] In this invention, the Ag2S / Cd 0.5 Zn 0.5 In S photocatalytic materials, Ag2S and Cd 0.5 Zn 0.5 The preferred mass ratio of S is 0.05 to 0.07:1.

[0017] In this invention, in step 1), the mixing is carried out under stirring conditions, and the stirring time is 2-3 hours, preferably 2.5 hours; The heating temperature is 150~250℃, preferably 180~220℃; the heating time is 20~25h, preferably 22~24h. The drying temperature is 50~80℃, preferably 60℃; the drying time is 10~15h, preferably 12~14h.

[0018] In this invention, in step 1), the cadmium source includes one or more of cadmium acetate, cadmium nitrate, and cadmium chloride, preferably cadmium acetate or cadmium nitrate, and more preferably cadmium acetate; the zinc source includes one or more of zinc acetate, zinc nitrate, and zinc chloride, preferably zinc acetate or zinc nitrate, and more preferably zinc acetate; the sulfur source includes one or more of thiourea, thioacetamide, and sodium sulfide, preferably thiourea or thioacetamide, and more preferably thiourea.

[0019] In this invention, in step 2), the silver source includes one or more of silver nitrate, silver acetate, and silver ammonia complexes, preferably silver nitrate; the sulfur source includes one or more of sodium sulfide, thioacetamide, thiourea, and sodium hydrosulfide, preferably sodium sulfide. The mixing is carried out under stirring conditions, and the stirring time is 5-20 min, preferably 8-15 min, and more preferably 10 min; The drying is carried out under light-protected conditions for 10-15 hours, preferably 12 hours.

[0020] In this invention, in step 3), the mixing is carried out under stirring conditions, and the stirring time is 2-3 hours, preferably 2.5 hours; The temperature of the hydrothermal reaction is 100~150℃, preferably 120~140℃; the reaction time is 2~5h, preferably 3~4h.

[0021] In this invention, in step 3), the drying temperature is 50~80℃, preferably 60~70℃; the drying time is 10~15h, preferably 12~14h.

[0022] This invention provides an Ag2S / Cd prepared by the above preparation method. 0.5 Zn 0.5 S photocatalytic materials.

[0023] The present invention also provides the above-mentioned Ag2S / Cd 0.5 Zn 0.5 Application of S photocatalytic materials in photocatalytic hydrogen evolution.

[0024] In this invention, the various reagents and materials used are shown in Table 1, and the experimental instruments are shown in Table 2.

[0025] Table 1. Reagents used in the experiment, their specifications, and manufacturers.

[0026] Table 2. Models and Manufacturers of Experimental Instruments

[0027] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0028] Example 1

[0029] 2 mmol zinc acetate dihydrate, 2 mmol cadmium acetate dihydrate, and 30 mmol thiourea were added to 60 mL of ethylenediamine-water solution (ethylenediamine to water volume ratio 2:1) and stirred for 2 h. The mixture was then transferred to a 100 mL Teflon-lined stainless steel reactor and reacted at 220 °C for 22 h. After the reaction, the reactor was allowed to cool naturally to room temperature. The solution was repeatedly washed with deionized water and ethanol, and the precipitate was collected by centrifugation and dried at 60 °C for 12 h to obtain Cd. 0.5 Zn 0.5 S powder, denoted as CZS; 2.72 g of silver nitrate was added to 40 mL of deionized water and stirred for 30 min to form solution A. 1.92 g of sodium sulfide nonahydrate (Na₂S·9H₂O) was added to 40 mL of deionized water to form solution B. Solutions A and B were mixed and stirred for 5 min. The mixture was washed three times with ethanol, centrifuged, and vacuum dried in the dark for 12 h to obtain Ag₂S nanoparticles. 100 mg of CZS and 5 mg of Ag₂S nanoparticles were mixed in 20 mL of deionized water and stirred for 2 h. The mixture was then transferred to a 50 mL Teflon-lined stainless steel reactor and reacted at 120 °C for 2 h. The mixture was washed repeatedly with deionized water and ethanol, and the precipitate was collected by centrifugation and dried at 60 °C for 12 h in a vacuum drying oven to obtain Ag₂S-modified CZS. The mass of Ag₂S was 5% of CZS, and the resulting catalyst was labeled as 5% Ag₂S / CZS.

[0030] Example 2

[0031] Unlike Example 1, in this example, 100 mg of CZS and 3 mg of Ag2S nanoparticles were used to prepare the catalyst, and the resulting catalyst was denoted as 3%Ag2S / CZS.

[0032] Example 3

[0033] Unlike Example 1, in this example, 100 mg of CZS and 7 mg of Ag2S nanoparticles were used to prepare the catalyst, and the resulting catalyst was denoted as 7%Ag2S / CZS.

[0034] Example 4

[0035] Unlike Example 1, in this example, 2 mmol of zinc acetate dihydrate, 2 mmol of cadmium acetate dihydrate, and 30 mmol of thiourea were added to 60 mL of ethylenediamine-water solution (ethylenediamine to water volume ratio of 2:1) and stirred for 2 h. Subsequently, the mixture was transferred to a 100 mL Teflon-lined stainless steel reactor and reacted at 170 °C for 22 h. After the reaction, the reactor was allowed to cool naturally to room temperature. The mixture was repeatedly washed with deionized water and ethanol, and the precipitate was collected by centrifugation and dried at 60 °C for 12 h to obtain Cd. 0.5 Zn 0.5 S powder; Take 100mg of Cd 0.5 Zn 0.5 The catalyst was prepared by combining S powder and 5 mg of Ag2S nanoparticles obtained in Example 1. The resulting catalyst was designated as 170℃ 5%Ag2S / CZS.

[0036] 1) Morphological and microstructural characteristics

[0037] (1) The microstructure, size, lattice fringes and exposed crystal faces of the catalyst prepared in Example 1 were observed by means of transmission electron microscopy (FEI Tecnai G20, Hillsboro, USA) and high-power transmission electron microscopy (HRTEM).

[0038] (2) Scanning electron microscope (SEM)

[0039] The microstructure, structure, and particle size of the samples obtained in Example 1 were observed using a scanning electron microscope (Sigma 300, Zeiss, Germany). Before testing, the samples were coated on conductive adhesive, sputtered with gold for 60 seconds, and then cleaned. The accelerating voltage was 350 V to 30 kV, and the working distance was 5 to 10 mm.

[0040] like Figure 1 As shown, the synthesized CZS sample consists of nanorods with an average length of approximately 300 nm. At 220 °C, the length of the nanorods increases, and the particles are relatively uniform and well-dispersed. Ag₂S / CZS exhibits clear lattice fringes, with a lattice spacing of 0.33 nm attributable to the (002) crystal plane of the CZS solid solution, and a lattice spacing of 0.24 nm corresponding to the (220) crystal plane of Ag₂S. HAADF-STEM mode indicates the coexistence of Ag, Zn, Cd, and S elements in the composite material, and that the elements exhibit a uniform distribution.

[0041] (3) Effect of specific surface area on photocatalytic activity

[0042] The specific surface area and related pore size distribution of CZS at 170℃, 5%Ag₂S / CZS at 170℃, CZS at 220℃, and 5%Ag₂S / CZS at 220℃ were characterized. Figure 2 As shown, the results indicate that although a higher specific surface area can increase the number of active sites and provide more surface for catalytic reactions, the increase in specific surface area is often accompanied by a large number of crystal defects, the formation of amorphous regions, or excessive grain fragmentation. Therefore, the resulting introduction of charge recombination centers can offset or even outweigh the benefits of increased surface area, ultimately leading to a decline in performance. Although the sample at 220℃ has a smaller specific surface area, it has higher crystallinity, fewer defects, a higher density of effective active sites, and better charge separation efficiency.

[0043] 2) Photoelectrochemical performance testing methods

[0044] In the three-electrode system, different photocatalysts were deposited on 5 mm × 5 mm ITO conductive glass as working electrodes, platinum (Pt) as counter electrodes, and silver / silver chloride (Ag / AgCl) electrodes as reference electrodes. The main methods for measuring photoelectrochemical performance included electrochemical impedance spectroscopy, transient photocurrent, and Mott-Schottky analysis.

[0045] Preparation of the working electrode: Weigh 10 mg of catalyst sample and add it to 300 μL of anhydrous ethanol. Disperse the sample by sonication for 5 min to ensure uniform dispersion. Then, divide the resulting suspension into three portions, each 10 μL, and uniformly drop-coat it onto ITO conductive glass, with a coating area of ​​5 mm × 5 mm. After coating, place the ITO glass in a clean petri dish and air-dry it at room temperature to obtain the working electrode.

[0046] (1) Electrochemical impedance spectroscopy (EIS)

[0047] EIS testing was used to study electrode process kinetics and electrode surface phenomena. The test was conducted at a 0 V bias (vs. Ag / AgCl) with 100 mL of 0.5 M anhydrous sodium sulfate (Na₂SO₄) solution as the electrolyte. The frequency range was 1000 Hz to 1 MHz, and the AC signal amplitude was 5 mV.

[0048] (2) Transient photocurrent measurement (TPCD)

[0049] When a semiconductor electrode is irradiated with visible light and the incident light energy is greater than the band gap, valence band electrons transition to the conduction band and migrate along the conduction wire to the other electrode, generating a photocurrent. The photocurrent intensity is affected by the incident light intensity and semiconductor properties. Photocurrent measurement can be used to analyze the generation efficiency and recombination behavior of photogenerated carriers. TPCD testing used a 300 W xenon lamp as the light source, 100 mL of 0.5 M Na2SO4 solution as the electrolyte, with both illumination and light-shielding times of 20 s, and a test bias voltage of 0 V.

[0050] like Figure 3 As shown in (a), the TPCD curves indicate that the photocurrent density of 5%Ag₂S / CZS at 220℃ is significantly higher than that of CZS at 170℃, 5%Ag₂S / CZS at 170℃, CZS at 220℃, and Ag₂S. This demonstrates that the introduction of Ag₂S enables effective separation of photogenerated carriers, resulting in more photogenerated electrons on the surface of the composite material, further accelerating the separation and transfer of photogenerated charges. Furthermore, as... Figure 3 (b) EIS test results show that 220 ℃ 5%Ag2S / CZS exhibits a smaller radius of curvature in the Nyquist plot and has a lower charge transfer resistance compared to other catalysts. Its electrons can be transferred to protons more quickly, thereby improving the transport efficiency of photogenerated carriers.

[0051] (3) Mott-Schottky test

[0052] The Mott-Schottky assay is used to evaluate the electrochemical properties of semiconductors, including semiconductor type, carrier concentration, and flat band potential. Combined with UV-vis DRS, the conduction and valence band positions can be deduced. The assay was performed in 100 mL of 0.5 M Na₂SO₄ electrolyte solution at frequencies of 500 Hz, 1000 Hz, and 1500 Hz.

[0053] The positive slope of the Mott-Schottky plots for CZS and Ag₂S at 220℃ indicates that both samples are n-type semiconductors. The Et of CZS and Ag₂S at 220℃ can be obtained from the intercepts on the horizontal axis. FB The values ​​are -0.50 V and -0.52 V vs. Ag / AgCl, respectively. After conversion, the conduction band (CB) values ​​of CZS and Ag2S at 220℃ are -0.40 V and -0.42 V, respectively, and the valence band (VB) values ​​are 1.16 V and 0.9 V, respectively.

[0054] 2) Photocatalytic hydrogen evolution activity and stability

[0055] The photocatalytic hydrogen evolution reaction was conducted using a fully automated online micro-gas analysis system (Labsolar-6A). A 300 W xenon lamp (HSX-F300) was used as a simulated solar light source. 20 mg of photocatalyst was uniformly dispersed in 100 mL of a 0.25 M sodium sulfide (Na₂S) / 0.35 M sodium sulfite (Na₂SO₃) aqueous solution and kept in suspension using a magnetic stirrer under visible light (λ>420 nm) irradiation. The reaction temperature was maintained at 25 °C using a water-cooling system. Before the start of the photocatalytic hydrogen evolution reaction, the entire reaction system was thoroughly evacuated to remove dissolved gases. The hydrogen production was quantitatively analyzed online using a gas chromatograph (GC-9790Ⅱ) equipped with a thermal conductivity detector and a 5 Å molecular sieve column, with argon as the carrier gas. Samples were injected hourly for a total of 3 hours, and the photocatalytic hydrogen evolution activity of the catalyst was evaluated based on the hydrogen production rate.

[0056] After 3 hours of photocatalytic reaction, the xenon lamp was turned off. The catalyst was then collected, centrifuged, dried, and the photocatalytic reaction test was repeated. Each cycle lasted 3 hours, and a total of 5 cycles were conducted, for a total of 15 hours of photocatalytic reaction, in order to evaluate the photocatalytic stability of the photocatalyst.

[0057] like Figure 4 As shown in (a), the 5% Ag₂S / CZS composite photocatalyst at 220℃ exhibited the best photocatalytic hydrogen evolution performance, with a hydrogen evolution rate of 78.31 mmol·g⁻¹. -1 ·h -1 The values ​​were 220℃ CZS (36.70 mmol·g). -1 ·h -1 ), Ag2S (2.40 mmol·g -1 ·h -1 ) 2.13 times and 36.76 times.

[0058] After five rounds of stability tests, 5%Ag2S / CZS at 170 ℃ retained only 62.00% of its initial photocatalytic hydrogen evolution activity, while 5%Ag2S / CZS at 220 ℃ maintained 78.54% of its activity. The stability decreased slightly, possibly due to photocorrosion of the catalyst.

[0059] 20 mg of the 5% Ag2S / CZS composite photocatalyst prepared in Example 1 at 220℃ was uniformly dispersed in different sacrificial agents, and the results were as follows: Figure 5 As shown in the figure. The results indicate that when a 0.25 M Na₂S / 0.35 M Na₂SO₃ mixed solution is used as a sacrificial agent, the catalyst exhibits the best hydrogen evolution activity, with a hydrogen evolution rate of 78.31 mmol·g⁻¹. -1 ·h -1When a 10 vol% lactic acid solution was used as a sacrificial agent, the hydrogen evolution rate was 3.19 mmol·g. -1 ·h -1 When 0.1 M ascorbic acid solution was used as a sacrificial agent, the hydrogen evolution rate was 2.91 mmol·g. -1 ·h -1 When a 10 vol% triethanolamine solution was used as a sacrificial agent, the hydrogen evolution rate was 1.90 mmol·g. -1 ·h -1 When a 10 vol% methanol solution was used as a sacrificial agent, the hydrogen evolution rate was 0.57 mmol·g. -1 ·h -1 .

[0060] As can be seen from the above embodiments, the present invention provides an Ag2S / Cd 0.5 Zn 0.5 This invention successfully prepared Ag₂S / CZS composite photocatalysts using a simple method, and investigated the effects of hydrothermal temperature on the crystal structure, microstructure, and photocatalytic hydrogen evolution performance of CZS. The results showed that CZS prepared at 220℃ exhibited a nanorod morphology of approximately 300 nm in size. This structure effectively inhibited nanoparticle aggregation, shortened the photogenerated carrier transport distance, and improved the utilization rate of visible light within the material, demonstrating superior photocatalytic activity. Analysis using various characterization methods revealed that increasing the hydrothermal temperature effectively narrowed the band gap of CZS, promoting the formation of an S-shaped heterojunction with interleaved bands between Ag₂S and CZS. This enabled efficient separation of photogenerated carriers while maximizing the preservation of the system's redox capabilities. The narrow band gap of Ag₂S extended the light absorption range of the composite material into the near-infrared region, and the formation of the S-shaped heterojunction with CZS synergistically promoted interfacial electron transport.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An Ag2S / Cd 0.5 Zn 0.5 The method for preparing S photocatalytic materials is characterized by... Includes the following steps: Step 1) Zinc source, cadmium source, sulfur source and ethylenediamine aqueous solution are mixed according to stoichiometric ratio to obtain a mixed solution. The obtained mixed solution is transferred to a reaction vessel and heated for reaction. After natural cooling, the obtained product is centrifuged, washed, and finally dried to obtain Cd. 0.5 Zn 0.5 S powder; Step 2) Dissolve the silver source and sulfur source in solvents according to the stoichiometric ratio of Ag2S. Mix the two solutions and react them. Then wash, centrifuge and dry them in sequence to obtain Ag2S nanoparticles. Step 3) Place Cd 0.5 Zn 0.5 S powder and Ag2S nanoparticles were mixed evenly in a solvent, stirred, and then subjected to a hydrothermal reaction. After the reaction was completed, the mixture was allowed to cool naturally, and then washed and dried sequentially to obtain Ag2S / Cd. 0.5 Zn 0.5 S photocatalytic materials; The Ag2S / Cd 0.5 Zn 0.5 In S photocatalytic materials, Ag2S and Cd 0.5 Zn 0.5 The mass ratio of S is 0.03~0.1:

1.

2. An Ag₂S / Cd mixture according to claim 1 0.5 Zn 0.5 The method for preparing S photocatalytic materials is characterized by... In step 1), the mixing is carried out under stirring conditions for 2-3 hours; The heating temperature is 150~250℃, and the heating time is 20~25h; The drying temperature is 50~80℃, and the drying time is 10~15h.

3. An Ag₂S / Cd mixture according to claim 1 or 2 0.5 Zn 0.5 The method for preparing S photocatalytic materials is characterized by... In step 1), the cadmium source includes one or more of cadmium acetate, cadmium nitrate, and cadmium chloride; the zinc source includes one or more of zinc acetate, zinc nitrate, and zinc chloride; and the sulfur source includes one or more of thiourea, thioacetamide, and sodium sulfide.

4. An Ag₂S / Cd mixture according to claim 3 0.5 Zn 0.5 The method for preparing S photocatalytic materials is characterized by... In step 2), the silver source includes one or more of silver nitrate, silver acetate, and silver ammonia complexes; the sulfur source includes one or more of sodium sulfide, thioacetamide, thiourea, and sodium hydrosulfide. The mixing is carried out under stirring conditions for 5 to 20 minutes; The drying process is carried out under light-protected conditions for 10-15 hours.

5. An Ag2S / Cd according to claim 1 or 4 0.5 Zn 0.5 The method for preparing S photocatalytic materials is characterized by... In step 3), the mixing is carried out under stirring conditions for 2-3 hours; The hydrothermal reaction is carried out at a temperature of 100-150℃ for 2-5 hours.

6. An Ag₂S / Cd according to claim 5 0.5 Zn 0.5 The method for preparing S photocatalytic materials is characterized by... In step 3), the drying temperature is 50~80℃ and the drying time is 10~15h.

7. The Ag₂S / Cd prepared by the preparation method according to any one of claims 1 to 6 0.5 Zn 0.5 S photocatalytic materials.

8. The Ag2S / Cd according to claim 7 0.5 Zn 0.5 Application of S photocatalytic materials in photocatalytic hydrogen evolution.

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