Cyano-bridged high-entropy material as well as preparation method and application thereof

Abstract

The invention discloses a cyano-bridged high-entropy material as well as a preparation method and application thereof. The preparation method of the cyano-bridged high-entropy material comprises the following steps: step 1, dissolving manganese acetate, cobalt acetate, cupric acetate and zinc acetate in ultrapure water, and adding PVP and sodium citrate to prepare a solution A; step 2, dissolving potassium nickelocyanate in ultrapure water to prepare a solution B, pouring the solution B into the container filled with the solution A after the solution B and the solution A are dissolved, introducing argon after the solution B and the solution A are mixed, discharging air in the container, and sealing to obtain a mixed solution A and B; and 3, transferring the container filled with the AB mixed solution into a hydrothermal reaction kettle, carrying out heating reaction at 50-80 DEG C for 14-18 hours, and then washing and drying to obtain the cyano-bridged high-entropy material. The invention provides the application of the cyano-bridged high-entropy material as a photocatalyst in hydrogen production by visible light photocatalytic decomposition of water, and the performance of hydrogen production by photocatalytic decomposition of water is effectively improved.

Description

TECHNICAL FIELD

[0001] The application relates to a cyanide-bridged high-entropy material and a preparation method thereof and application thereof in hydrogen production by water photolysis. BACKGROUND

[0002] With the transformation of global energy structure towards cleanization, hydrogen energy is regarded as a key energy carrier due to its zero-carbon emission characteristics, and the water photolysis hydrogen production technology has become the core direction of the hydrogen energy strategy due to its cleanness and sustainability. The photocatalytic hydrogen production (H2) on semiconductor materials represents an important way for the production of green hydrogen. However, the current water photolysis hydrogen production still faces the following challenges: high carrier recombination rate, insufficient wide-spectrum response, poor photocatalytic stability and the like. The development of photocatalysts with excellent physical and chemical properties is the key to realizing efficient solar hydrogen production, and therefore has become the main research focus in this field. Cyanide-bridged framework is a kind of porous or layered structure material formed by connecting metal ions with cyanide (-CN) as bridging ligand, which has shown remarkable advantages in the field of photocatalysis in recent years. As a new emerging photocatalyst, it has many unique advantages compared with traditional semiconductor photocatalysts. First, structural tunability and active site design: the cyanide-bridged framework can flexibly regulate the topological structure and electronic properties of the framework by selecting different metal ions (such as Fe , Co , Cu , Ni 2+ and the like) and organic ligands. Second, excellent light absorption and charge transport performance: the metal-to-ligand charge transfer (MLCT) characteristics of the cyanide-bridged complex enable it to have strong absorption in the visible light or even near-infrared region, for example, the light response range of the Fe-CN-Cu system can reach 400-800 nm; third, efficient charge separation: the cyanide as an electron transport channel can accelerate the migration of photo-generated electrons from the photosensitive group (such as metalloporphyrin) to the catalytically active site, reduce the recombination of photo-generated electrons and holes, and improve the carrier lifetime. In recent years, high-entropy materials (HEMs) have shown broad application prospects in the fields of catalysis, energy, environment and the like due to their adjustable composition, rich active centers, unsaturated coordination and structural stability and the like. The concept of "high entropy" was first proposed by Yeh and Cantor in high-entropy alloys (HEAs), wherein HEAs are usually defined as alloys containing a relatively high concentration (5-35 at.%) of multiple elements instead of traditional single main composition, and the limitation of multiple atomic species in the same lattice realizes the significant expansion of the tuning range of the catalytically active sites through the enhanced entropy contribution. In addition, the significant lattice distortion in HEMs reduces the energy of the whole system, thereby being beneficial to the activation and transmission of active species.

[0003] It is a challenging work to optimize the photocatalytic hydrogen production performance of the cyanide bridging framework again in combination with the high-entropy concept, which can provide certain reference significance for the subsequent research of high-entropy materials in the field of photocatalytic hydrogen production. SUMMARY

[0004] In order to solve the problems such as high carrier recombination rate and poor photocatalytic stability in the current hydrogen production by water photolysis, the application provides a cyanide-bridged high-entropy material (MnCoCuZn)Ni(CN)4, a preparation method thereof and an application thereof in hydrogen production by water photolysis. Experimental results show that the synergistic effect of multiple metals and the lattice distortion of high-entropy materials can significantly accelerate charge transfer and enhance light absorption capacity, thereby obtaining maximum photocatalytic activity under visible light and maintaining long photocatalytic stability, thereby effectively improving the photocatalytic hydrogen production performance.

[0005] The technical solutions of the application are described below

[0006] In a first aspect, the application provides a preparation method of a cyanide-bridged high-entropy material, comprising the following steps: Step 1: Dissolve Mn(CH3COO)2·4H2O, Co(CH3COO)2·4H2O, Cu(CH3COO)2·H2O and Zn(CH3COO)2·H2O in ultrapure water, add PVP and sodium citrate to prepare A liquid, wherein 0.1-0.2 g of Mn(CH3COO)2·4H2O, 2.0-4.0 g of PVP and 0.8-1.0 g of sodium citrate are added per 60 mL of ultrapure water; Step 2: Dissolve K2Ni(CN)4 in ultrapure water to prepare B liquid, wherein the feeding ratio of K2Ni(CN)4 to ultrapure water is 3.0-3.5 mmol:20 mL. After dissolution, pour the B liquid into the container containing the A liquid, and after mixing, introduce argon to discharge the air in the container and seal it to obtain AB mixed liquid; Step 3: Transfer the container containing the AB mixed liquid to a hydrothermal reaction kettle, heat at 50-80℃ for 14-18 hours, then wash and dry to obtain a cyanide-bridged high-entropy material; The feeding molar ratio of Mn(CH3COO)2·4H2O, Co(CH3COO)2·4H2O, Cu(CH3COO)2·H2O, Zn(CH3COO)2·H2O and K2Ni(CN)4 is 1:1.3-1.5:1.3-1.5:1.2-1.4:5.2-5.4.

[0007] Preferably, in step 3, the reaction temperature is 50℃ and the reaction time is 16h.

[0008] Preferably, in step 3, the washing is repeated alternately with ethanol and ultrapure water.

[0009] Preferably, in step 3, the drying refers to natural air drying at room temperature, and the air drying time is 48-50h.

[0010] In a second aspect, the present application provides a cyanide-bridged high-entropy material prepared by the preparation method of the first aspect.

[0011] In a third aspect, the present application provides an application of the cyanide-bridged high-entropy material of the second aspect as a photocatalyst in the photocatalytic decomposition of water to produce hydrogen under visible light.

[0012] The application can be specifically implemented by the following operation: the cyanide-bridged high-entropy material is used as a photocatalyst, ruthenium bipyridine is used as a photosensitizer, triethanolamine (TEOA) is used as a sacrificial agent, and a uniform suspension is formed by dispersing in a mixed solvent of DMF and water, and hydrogen is generated by decomposing water under an argon atmosphere and visible light irradiation.

[0013] In some embodiments, the volume ratio of DMF to water in the mixed solvent of DMF and water is 3-5:1, preferably 4:1, and 1.0-2.0 mg of photocatalyst, 9.0-10.0 mg of photosensitizer and 1.0-2.0 mg of sacrificial agent are added per 10 mL of mixed solvent of DMF and water.

[0014] In some embodiments, the visible light is provided by a xenon lamp (λ>420nm) as a light source.

[0015] Compared with the prior art, the present application has the following beneficial effects: The present application introduces the concept of high-entropy into cyanide-bridged materials, limits multiple atomic species in the same lattice, significantly expands the tuning range of catalytic active sites through enhanced entropy contribution, and effectively improves the performance of water photolysis to produce hydrogen through the synergistic effect of metals. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The X-ray powder diffraction comparison chart of the high-entropy materials (MnCoCuZn)(Ni(CN)4) (HEM-1, HEM-2) prepared in Examples 1 and 2 and the comparative sample CoNi(CN)4 (Co-Ni); Figure 2 The infrared comparison chart of the high-entropy materials (HEM-1, HEM-2) prepared in Examples 1 and 2 and the comparative sample Co-Ni; Figure 3 The scanning electron microscope chart of the high-entropy materials (HEM-1, HEM-2) prepared in Examples 1 and 2 and the comparative sample Co-Ni; Figure 4The sample element distribution map obtained by transmission electron microscopy of the high-entropy material (HEM-1) prepared in Example 1; Figure 5 The element energy spectrum information (EDS) obtained by transmission electron microscopy of the high-entropy material (HEM-1) prepared in Example 1; Figure 6 The light emission spectrum (PL) comparison chart of the high-entropy material (HEM-1) prepared in Example 1 and its comparative sample Co-Ni; Figure 7 The photocatalytic water decomposition hydrogen production performance chart of the high-entropy material (HEM-1) prepared in Example 1 and its comparative sample Co-Ni. DETAILED DESCRIPTION

[0017] The application will be further described below by examples, which only illustrate the method of the application and do not limit the scope of application of the application.

[0018] Example 1

[0019] The preparation of a high-entropy material bridged by cyanide is completed according to the following steps: I. Preparation: Mn(CH3COO)2·4H2O, Co(CH3COO)2·4H2O, Cu(CH3COO)2·H2O, Zn(CH3COO)2·H2O, the mass is 0.138g, 0.196g, 0.160g, 0.147g respectively, dissolved in 60ml of ultrapure water, after stirring at a stirring speed of 600r / min for 30min, 0.8g of sodium citrate and 4.0g of PVP (number average molecular weight 40000) are added, and after stirring at a stirring speed of 600r / min for 30min, it is recorded as A liquid, and the next step is carried out; II. Preparation of high-entropy material: take potassium nickel cyanide K2Ni(CN)4 0.72g dissolved in 20ml of ultrapure water, record as B liquid, pour B liquid into A liquid and place in a 100ml blue cap bottle, introduce argon to expel air and seal, transfer to a hydrothermal reaction kettle, place in a 50℃ oven and heat for 16h, then wash repeatedly with ethanol and ultrapure water for two times, and air dry for 48h to obtain a high-entropy material, recorded as HEM-1.

[0020] Example 2

[0021] The preparation of a high-entropy material bridged by cyanide is completed according to the following steps: I. Preparation: Mn(CH3COO)2·4H2O, Co(CH3COO)2·4H2O, Cu(CH3COO)2·H2O, Zn(CH3COO)2·H2O, the mass is 0.138g, 0.196g, 0.16g, 0.147g respectively, dissolved in 60ml ultrapure water, after stirring at a stirring speed of 600r / min for 30min, 0.6g of sodium citrate and 4.0g of PVP (number average molecular weight 40000) were added, and the mixture was stirred at a stirring speed of 600r / min for 30min, and was recorded as A liquid, and the next step was carried out; II. Preparation of high-entropy material: 0.72g of potassium nickelocyanide K2Ni(CN)4 was dissolved in 20ml of ultrapure water, and was recorded as B liquid. B liquid was poured into A liquid and placed in a 100ml blue cap bottle. After argon was introduced to replace air, the bottle was sealed and transferred to a hydrothermal reaction kettle. The bottle was heated at 50℃ for 8h, and then washed repeatedly with ethanol and ultrapure water for two times. After natural air drying for 48h, a high-entropy material was obtained, and was recorded as HEM-2.

[0022] Comparative Example 1

[0023] The present comparative example provides a cyano-bridged photocatalyst and a preparation method thereof, comprising the following steps: (1) 0.3g of cobalt acetate Co(CH3COO)2·4H2O was dissolved in 20ml of ultrapure water, 0.25g of sodium citrate and 1.0g of PVP were added, and the mixture was fully dissolved to obtain A liquid; (2) 0.36g of potassium nickelocyanide was dissolved in 20ml of ultrapure water, and was recorded as B liquid; (3) B liquid was poured into the prepared A liquid, and was placed on a magnetic stirrer with a stirring speed of 500r / min. After stirring for 8h, the mixture was washed repeatedly by centrifugation with ethanol and ultrapure water for three times, and was naturally air dried for 48h to obtain a comparative sample CoNi(CN)4. Experimental Example 3: The structure of the photocatalysts prepared in Example 1, Example 2 and Comparative Example 1 was tested.

[0024] As shown in Figure 1 FIG. 1, the XRD of the high-entropy material and the comparative sample Co-Ni is shown in the figure. The comparative sample Co-Ni has strong characteristic peaks at 20.2°, 24.8°, 30.1° and 35.2°, while the high-entropy material (HEM-1, HEM-2) has very strong diffraction peaks at 17.2°, 24.4°, 34.6° and 38.9°, and the peak intensity of HEM-1 is obviously higher than that of HEM-2. Since the reaction period of HEM-2 is shorter, it is speculated that HEM-2 is a reaction intermediate of HEM-1. It is also found that unlike the single component Co-Ni, the high-entropy material forms a completely new phase; As shown inFigure 2 As shown, the FTIR spectra of the high-entropy materials (HEM-1, HEM-2) and the control sample Co-Ni show that the three samples have the same characteristic peak, specifically, at 2153 cm⁻¹. -1 The nearby peak is related to the stretching vibration of the -CN functional group, 1623 cm⁻¹. -1 and 3500cm -1 The nearby peaks are related to the stretching vibrations of the -OH functional group; The above results indicate that the -CN functional group was retained during the synthesis of the high-entropy material, proving that the material has a cyano-bridged structure. The characteristic peak of -OH indicates that the high-entropy material retains coordinated water and interlayer water, consistent with the single-component Co-Ni. like Figure 3 As shown in the figure, the scanning electron microscope schematic diagram of the high-entropy material shows the morphology of the high-entropy sample. The results show that the high-entropy material has a cubic structure with a size of about 500 nanometers and a uniform size distribution. The single component Co-Ni has a sheet-like structure with a size of about 2 micrometers. like Figure 4 , 5 As shown, the transmission electron microscope mapping and elemental energy dispersive spectroscopy (EDS) schematic diagram of the high entropy material (HEM-1) are shown. The results show that the Mn, Co, Ni, Cu, Zn, C, N and O elements are relatively uniformly distributed in the high entropy material, which proves that the multi-metal has successfully entered the cyano-bridging framework. like Figure 6 As shown, the photoluminescence (PL) spectra of the high-entropy material HEM-1 and the control sample Co-Ni were used to evaluate the transport and separation efficiency of photoexcited charge carriers. It can be noted that the PL peak intensity of the high-entropy material is significantly reduced compared to Co-Ni with a single metal element, confirming a significant decrease in the overall PL emission intensity. This result indicates that the vacancies generated by the lattice distortion of the high-entropy material, as well as the multi-metal synergistic effect—the cocktail effect—effectively reduce the recombination of photogenerated charge carriers.

[0025] Experimental Example 4: This experimental example tests the photocatalytic hydrogen production performance of the photocatalysts prepared in Example 1 and Comparative Example 1.

[0026] This embodiment measures and analyzes the photocatalytic hydrogen production rate of the high-entropy material (HEM-1) prepared in Example 1 and the Co-Ni photocatalyst prepared in Comparative Example 1.

[0027] Photocatalytic H2 hydrogen production measurement system: The photocatalytic water splitting hydrogen production experiment involved in this embodiment was carried out in a 500mL top-transparent irradiation reaction glass container, which was connected to a closed gas circulation and evacuation system (Labsolar-6A, Beijing Bofei Technology Co., Ltd.).

[0028] During the experiment, 2 mg of photocatalyst and 9 mg of photosensitizer (ruthenium bipyridine) were dispersed in 10 mL of solvent (DMF:H2O=4:1), and 1 ml of sacrificial agent triethanolamine (TEOA) was added. Before irradiation with a 300 W xenon lamp with a filter (λ≥420 nm) as a visible light source, the mixed solution was injected into the photocatalytic reaction container, vacuumed several times to remove air and other gases, and the photocatalytic decomposition of water to produce hydrogen test was carried out under argon conditions. During the photocatalytic reaction process, the solution should be continuously stirred, and the reaction temperature was maintained at 25°C by circulating cooling water. The generated hydrogen was detected by a gas chromatograph with nitrogen as the carrier gas.

[0029] The photocatalytic hydrogen evolution performance of the prepared photocatalyst under visible light (λ≥420 nm) was evaluated: Results analysis: As shown in Figure 7 , the performance comparison chart of the high-entropy material (HEM-1) and the comparative sample Co-Ni for the photocatalytic decomposition of water to produce hydrogen, the hydrogen production rate of the comparative sample Co-Ni was 16.15 mmol·h- 1 ·g- 1 , while the hydrogen production rate of the high-entropy material was 24.93 mmol·h- 1 ·g- 1 , which was significantly improved by 1.5 times, proving that the introduction of the high-entropy concept into the photocatalyst significantly expanded the tuning range of the catalytic active sites through the enhanced entropy contribution of the same lattice, and the synergistic effect of multiple metals could significantly improve the performance of the photocatalytic decomposition of water to produce hydrogen.

Claims

1. A method of making a cyano-bridged high-entropy material, characterized by: The preparation method comprises the following steps: Step 1: Mn(CH3COO)2·4H2O, Co(CH3COO)2·4H2O, Cu(CH3COO)2·H2O and Zn(CH3COO)2·H2O are dissolved in ultrapure water, PVP and sodium citrate are added to prepare A liquid, wherein 0.1-0.2 g of Mn(CH3COO)2·4H2O, 2.0-4.0 g of PVP and 0.8-1.0 g of sodium citrate are added to 60 mL of ultrapure water; Step 2: K2Ni(CN)4 is dissolved in ultrapure water to prepare B liquid, wherein the feeding ratio of K2Ni(CN)4 to ultrapure water is 3.0-3.5 mmol: 20 mL, after dissolution, the B liquid is poured into a container containing the A liquid, after mixing, argon is introduced to remove the air in the container, and then sealed to obtain AB mixed liquid; Step 3: The container containing the AB mixed liquid is transferred to a hydrothermal reaction kettle, heated at 50-80℃ for 14-18 hours, then washed and dried to obtain a cyan-bridged high-entropy material; The feeding molar ratio of Mn(CH3COO)2·4H2O, Co(CH3COO)2·4H2O, Cu(CH3COO)2·H2O, Zn(CH3COO)2·H2O and K2Ni(CN)4 is 1:1.3-1.5:1.3-1.5:1.2-1.4:5.2-5.

4.

2. The production method according to claim 1, characterized by: In step 3, the reaction temperature is 50℃, and the reaction time is 16h.

3. The production method according to claim 1, wherein: In step 3, the washing is repeated alternately with ethanol and ultrapure water.

4. The production method according to claim 1, wherein: In step 3, the drying refers to natural air drying at room temperature, and the air drying time is 48-50h.

5. A cyan-bridged high-entropy material prepared by the preparation method of any one of claims 1-4.

6. Application of the cyan-bridged high-entropy material of claim 5 as a photocatalyst in visible light photocatalytic decomposition of water to produce hydrogen.

7. Use according to claim 6, wherein: The application specifically adopts the following operation: the cyan-bridged high-entropy material is used as a photocatalyst, ruthenium bipyridine is used as a photosensitizer, and triethanolamine is used as a sacrificial agent, which are dispersed in a mixed solvent of DMF and water to form a uniform suspension, and hydrogen is generated by decomposing water under argon atmosphere and visible light irradiation.

8. Use according to claim 7, wherein: The volume ratio of DMF to water in the mixed solvent of DMF and water is 3-5:1, 1.0-2.0 mg of photocatalyst, 9.0-10.0 mg of photosensitizer and 1.0-2.0 mg of sacrificial agent are added to every 10 mL of mixed solvent of DMF and water.

9. The use according to claim 7, wherein: The visible light is provided by a xenon lamp as a light source.

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