Preparation and application of a sandwich-type polyacid-based metal-organic hybrid material

Abstract

This invention relates to the preparation and application of a sandwich-type polyacid-based metal-organic hybrid material. The purpose of this invention is to solve the problems of poor stability and low conductivity of polyacid-based hybrid materials as electrode materials for hydrogen evolution in water electrolysis. It provides a method for preparing an electrode material that can improve the performance of hydrogen evolution in water electrolysis. The chemical formula of the sandwich-type polyacid-based metal-organic hybrid material of this invention is C0. 24 H 148 Cu4P 127 Mo 24 N 24 O 127 The synthesis method involves preparing sodium molybdate, copper sulfate, ethylenediaminetetraacetic acid, phosphoric acid, and deionized water via a hydrothermal self-assembly principle. This sandwich-type polyacid-based organometallic hybrid material C... 24 H 148 Cu4P 127 Mo 24 N 24 O 127 As a precursor, a copper-molybdenum bimetallic derivative electrode material Cu2S-MoS2@CC was prepared and applied to the catalytic electrolysis of water for hydrogen evolution reaction. The electrode material was used at a current density of 10 mA / cm². 2 The overpotential of the Cu2S-MoS2@CC material is 87 mV, and the Tafel slope is 31.9 mV dec. ‑1 The material exhibits an electrochemically active area of ​​83.28 mV and can continuously evolve hydrogen for 24 hours. This invention provides a technical route for the preparation of polyacid-based organometallic hybrid materials and for the preparation of polyacid-based metal-based dual-metal compound catalysts for hydrogen evolution through water electrolysis.

Description

Technical Field

[0001] This invention relates to a method for preparing and applying a sandwich-type polyacid-based metal-organic hybrid material. Background Technology

[0002] Energy, along with materials and information, is one of the three pillars of modern science and technology, serving as the material foundation for human societal development. In recent years, with the rapid development of global socio-economic development and industrialization, human demand for energy has been increasing. The reserves of traditional non-renewable energy sources, such as coal, oil, and natural gas, are gradually depleting, and the environmental pollution and greenhouse effect they cause during use are becoming increasingly prominent, posing a significant challenge to human society in its pursuit of sustainable development. Hydrogen, as a potential green energy carrier and possessing extremely high energy density (143 MJ / kg), is currently considered one of the leading energy sources capable of mitigating the excessive use of fossil fuels and serving as a key component of the future energy framework. Electrolysis of water is an effective method for producing hydrogen; the hydrogen evolution reaction (HER) in an acidic medium produces 4H₂O. + + 4e − →2H₂, which in an alkaline medium is 4H₂O + 4e⁻ − →2H2+ 4OH − This reaction process requires a high activation energy, and adding a highly active HER electrocatalyst is a feasible way to reduce energy consumption. The electrocatalyst is one of the key factors determining the efficiency and cost of catalytic hydrogen production. Precious metal catalysts such as platinum have been widely used in previous water electrolysis hydrogen production processes. These catalysts have excellent electrocatalytic performance, but their low global reserves and high cost indirectly increase the cost of hydrogen production, thus hindering the development of hydrogen energy.

[0003] In recent years, significant progress has been made in exploring non-precious metal electrocatalysts such as carbides, nitrides, oxides, phosphides, sulfides, selenides, and carbon-based materials. Among these newly developed electrocatalysts, molybdenum disulfide (MoS2) catalysts have attracted considerable attention due to their unique graphite-like two-dimensional (2D) structure, hydrogen adsorption free energy close to that of Pt, suitable Gibbs free energy, and low cost. MoS2 is a potentially ideal electrocatalyst for hydrogen production. However, MoS2 alone exhibits poor conductivity and limited exposure of active sites, restricting its inherent catalytic performance. The intrinsic activity of the unsaturated Mo- and S- edges can be enhanced by introducing a second metal sulfide, modifying individual MoS2 materials into composite nanostructures with more active sites to improve the hydrogen evolution performance of bimetallic sulfides in water electrolysis. Alternatively, MoS2-based composite materials can be combined with highly conductive matrices, such as carbon cloth (CC), carbon fiber paper (CF), and nickel foam (NF), to improve conductivity while preventing material aggregation. Carbon cloth is widely used as an ideal conductive matrix for loading active materials due to its stability over a wide pH range (including acidic and alkaline solutions) and its ease of modification.

[0004] Polyacid-based organometallic precursors are ideal pre-assembly platforms for synthesizing various bimetallic electrocatalysts. They can provide a variety of transition metals, and due to their fixed structure and high crystallinity, they can facilitate the formation of bimetallic sources with specific ratios. However, existing copper-molybdenum polyacid-based organometallic compounds generally suffer from low copper-molybdenum content, resulting in bimetallic sulfide electrode materials with low catalytic activity in water electrolysis for hydrogen evolution. Therefore, preparing novel polyacid-based organometallic compounds, especially those with high copper-molybdenum ratios, to improve the HER catalytic activity of their derived bimetallic electrocatalysts remains a technical challenge in the field of water electrolysis for hydrogen evolution. Summary of the Invention

[0005] The purpose of this invention is to address the problems of poor stability and low conductivity of polyacid-based hybrid materials as electrode materials for hydrogen evolution in water electrolysis. To improve their hydrogen evolution performance in water electrolysis, this invention provides a method for preparing and applying a sandwich-type polyacid-based metal-organic hybrid material.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0007] 1. Preparation of reaction solution with pH value of 4~4.5: Add appropriate amounts of sodium molybdate, copper sulfate, ethylenediaminetetraacetic acid and phosphoric acid to distilled water and stir evenly. Then adjust the pH value to 4~4.5 to obtain a reaction solution with pH value of 4~4.5.

[0008] The molar ratio of sodium molybdate to copper sulfate mentioned in step one is (0.25-0.3):(0.25-0.35).

[0009] The molar ratio of sodium molybdate to ethylenediaminetetraacetic acid mentioned in step one is (0.25-0.3):(0.6-0.7).

[0010] The volume ratio of sodium molybdate to phosphoric acid in step one is (0.25-0.3) mmol: (1-3) mL;

[0011] The molar ratio of sodium molybdate to distilled water in step one is (0.25-0.3) mmol: (10-15) mL;

[0012] 2. The reaction solution with a pH of 4-4.5 prepared in step 1 is transferred to a polytetrafluoroethylene reactor and reacted at 160℃ for 4 days. After the reaction solution is cooled to room temperature, it is washed to obtain reddish-brown blocky crystals, which is a sandwich-type polyacid-based organometallic hybrid material. The chemical formula of this hybrid material is (C2H4N2H6). 12 {Cu4[Mo6O 12 (OH)3]4}{PO4}8{HPO4}8·2H3O·H2O, wherein C2H4N2H6 is ethylenediamine; the crystals are reddish-brown and massive in appearance; the crystal system is triclinic; the space group is […]. P -1; cell parameters are a =13.4175(6) Å, b =23.9015(10) Å, c =26.8323(12) Å, α=111.9630(10)°, β=103.5640(10)°, γ=93.1980(10)°, V =7659.1(6) Å 3 ;

[0013] The synthesized crystal was subjected to X-ray single-crystal testing, and the structural analysis data are shown in Table 1.

[0014] Table 1 Crystal Data

[0015] Chemical formula <![CDATA[C 24 A 148 Cu4P 127 Mo 24 N 24 O 127 ]]> molecular weight 5857.64 Crystal system Triclinic Space Group P-1 a / Å 13.4175(6) b / Å 23.9015(10) c / Å 26.8323(12) α / deg 111.9630(10) β / deg 103.5640(10) γ / deg 93.1980(10) <![CDATA[V / Å 3 ]]> 7659.1(6) Z 2 <![CDATA[D calcd / g cm −3 ]]> 2.42 T / K 293(2) Refl. Unique 26717 <![CDATA[R int ]]> 0.0334 <![CDATA[GOF on F 2 ]]> 1.003 <![CDATA[R1 / wR2[I>2 σ(I)] a, b ]]> 0.0838 / 0.2673

[0016] a R 1 = ∑║ F o │-│ F c ║ / ∑│ F o │, b wR 2 = {∑[ w ( F o 2 - F c 2 ) 2 ] / ∑[ w ( F o 2 ) 2 ]} 1 / 2

[0017] III. Method for preparing a sandwich-type polyacid-based metal-organic hybrid material for hydrogen evolution by water electrolysis: 100 mg of the material prepared in Example 1 and 100 mg of thiourea were mixed evenly and dissolved in 30 mL of distilled water. The mixture was stirred thoroughly for 60 min. The reaction solution was then transferred to a 50 mL polytetrafluoroethylene reactor and reacted at 200 °C for 24 h. After the temperature of the reaction solution was lowered to room temperature, it was washed to obtain a black bimetallic sulfide crystalline material Cu2S-MoS2.

[0018] In step three, the stirring and mixing reaction time at room temperature is 0.5-1 h.

[0019] In step three, the molar ratio of copper-molybdenum polyacid metal-organic hybrid material to thiourea is 1:(140-160).

[0020] In step three, the hydrothermal reaction temperature is 180-200 ℃, and the time is 24 h.

[0021] IV. 5 mg of bimetallic sulfide Cu2S-MoS2 crystalline material was dissolved in 375 mL of distilled water, 125 mL of ethanol, and 10 μL of Nafion solution to prepare a slurry. The slurry was ultrasonicated for 2 h to obtain a uniformly dispersed mixture. This mixture was then drop-coated onto both sides of a pre-weighed, pre-treated carbon cloth (0.0323 g), and dried at room temperature to obtain the working electrode Cu2S-MoS2@CC, used for electrochemical testing. The carbon cloth loading was 10 mg.

[0022] In step four, the volume of the mixture transferred by the pipette is 30-50 μL.

[0023] In step four, the carbon cloth is ultrasonicated with acetone, ethanol, and distilled water for 30 min each, then treated with an appropriate amount of nitric acid in a reaction vessel at 100 degrees Celsius for 2 h, cooled to room temperature, cleaned with distilled water, and dried at 60 degrees Celsius for later use.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] I. This invention is the first to successfully prepare a sandwich-type polyacid-based organometallic hybrid material using simple inorganic raw materials such as sodium molybdate, copper sulfate, ethylenediaminetetraacetic acid, and phosphoric acid via a one-step hydrothermal synthesis method. Single-crystal X-ray diffraction results show that the unit cell of this material is composed of {Cu4[(Mo6O]2}} 12 Composed of (OH)3]4}{PO4}8{HPO4}8 units, protonated ethylenediamine, protonated water, and lattice water, its structure contains four types of crystallographic copper ions. Each copper ion forms a six-coordinate octahedral structure with six adjacent oxygen atoms. Six molybdenum atoms coordinate with different oxygen atoms to form six-coordinate octahedral structures, forming a six-membered ring. The Mo-Mo bond length ranges from 2.585 to 2.597 Å. Four different phosphorus atoms are on one side of the six-membered ring. One phosphorus atom is in the middle and connected to the ring by three μ-3 oxygen atoms, while the other three phosphorus atoms are connected to the ring by μ-2 oxygen atoms around the ring. Each phosphorus atom has a tetrahedral structure. The coordination of phosphorus atoms on the other side of the six-membered ring is the same as on this side. The basic unit of this compound contains four types of CuP4Mo6O 31 The monomers are in a relative relationship. They are respectively connected to [Mo6P4O] 31 The building blocks constitute Cu[Mo6P4]2 dimer.

[0026] In addition, this sandwich-type polyacid-based metal-organic hybrid material contains a large number of water molecules and ethylenediamine. These water molecules and ethylenediamine can bind isolated Cu[P4Mo6O] through hydrogen bonding. 31 The series connection of polyacid anion clusters gives the polyacid-based metal-organic hybrid material a two-dimensional structure, which expands the electron and proton conduction pathway from isolated polyacid clusters to polyacid-water-polyacid conduction. This increase in multiple electron / proton transport channels can improve the conductivity of the hybrid material.

[0027] II. This invention starts with simple inorganic raw materials such as sodium molybdate, copper sulfate, ethylenediaminetetraacetic acid, and phosphoric acid, and forms a multi-acid-based organometallic compound (H3NCH2CH2NH3) within a certain acidity and temperature range through the "self-assembly principle". 12 {Cu4[Mo6O 12 The raw material price is relatively low, and the yield is relatively high, based on 80% molybdenum.

[0028] III. The polyacid-based organometallic compound is composed of {Cu4[Mo6O] 12 The compound consists of [OH)3]4}{PO4}8{HPO4}8 units, protonated ethylenediamine, protonated water, and lattice water. The basic unit of this compound contains four CuP4Mo6 monomers, with copper respectively bonded to [Mo6P4O] 31]2 The building blocks are composed of Cu[Mo6P4O 31 MoS2 dimer. The molar ratio of copper to molybdenum is 1:12. While providing bimetallic molybdenum and copper, the higher proportion of molybdenum optimizes the morphology and / or electronic structure of MoS2, thereby improving the catalytic activity of HER.

[0029] IV. A sandwich-type polyacid-based metal-organic hybrid electrode material prepared in this embodiment. Its performance at 10 mA / cm² was measured. 2 At a given current density, the overpotential is 87 mV, the Tafel is 31.9 mV / dec, and the electrochemical active area is 83.28 mF / cm². 2 This method can stably and continuously produce hydrogen through water electrolysis for 24 hours. This result indicates that this unique structure increases the electron / proton conduction pathway, making electron / proton conduction easier and faster, which is beneficial to improving the stability and conductivity of hydrogen evolution during water electrolysis. Therefore, this method provides a research model for hydrogen evolution through water electrolysis using polyacid-based organometallic hybrid materials. Attached Figure Description

[0030] Figure 1 Example 1: Cu[Mo6P4O] in a sandwich-type multi-acid-based organometallic hybrid material 31 ]2 Dimer structure;

[0031] Figure 2 Example 1: A two-dimensional structural diagram of a sandwich-type multi-acid-based metal-organic hybrid material;

[0032] Figure 3 This is a schematic diagram of hydrogen bond formation in a unit cell of a sandwich-type polyacid-based metal-organic hybrid material, as shown in the example.

[0033] Figure 4 This is a schematic diagram of hydrogen bond formation in a two-dimensional structure of a sandwich-type multi-acid-based metal-organic hybrid material, as shown in the example. The sky-blue octahedron is copper, the dark blue octahedron is molybdenum, and the pink tetrahedron is phosphorus.

[0034] Figure 5 Example 1: A schematic diagram of hydrogen bond formation in the two-dimensional structure of a sandwich-type multi-acid-based metal-organic hybrid material.

[0035] Figure 6 The infrared spectrum of a sandwich-type polyacid-based metal-organic hybrid material is shown in the example.

[0036] Figure 7 Example 1: X-ray powder diffraction pattern of Cu2S-MoS2@CC, a bimetallic sulfide derived from a sandwich-type polyacid-based metal-organic hybrid material.

[0037] Figure 8 The X-ray photoelectron spectroscopy (XPS) spectrum of Cu2S-MoS2@CC obtained in Example 1 is shown below; (a) represents Cu2p, (b) represents S2p, (c) represents Mo3d, and (d) is the full XPS spectrum.

[0038] Figure 9 The images shown are scanning electron microscope (SEM) images and electron energy dispersive spectroscopy (EDS) images of Cu2S-MoS2@CC obtained in Example 1; (a)-(b) are images of Cu2S-MoS2@CC electrode material at different magnifications, and (c), (d), (e), and (f) are surface scan images of selected regions and electron energy dispersive spectroscopy images of S, Mo, and Cu.

[0039] Figure 10 The following are characterization diagrams of the hydrogen evolution performance of Cu2S-MoS2@CC and carbon cloth obtained in Example 1: (a) Comparison of overpotential between Cu2S-MoS2@CC and carbon cloth, (b) Comparison of Tafel slope between Cu2S-MoS2@CC and carbon cloth, (c) Cyclic voltammetry diagram of Cu2S-MoS2@CC, and (d) Comparison of electrochemical active area between Cu2S-MoS2@CC and carbon cloth.

[0040] Figure 11 The following are comparison diagrams of hydrogen evolution by water electrolysis of Cu2S-MoS2@CC and carbon cloth obtained in Example 1; 11(a) is a comparison diagram of AC impedance of Cu2S-MoS2@CC and carbon cloth (the equivalent circuit diagram and the enlarged AC impedance diagram in the high frequency region are inserted inside), 11(b) is a current-time stability diagram of Cu2S-MoS2@CC, 11(c) is a cyclic voltammetry diagram of carbon cloth, and 11(d) is a current-time stability diagram of carbon cloth. Detailed Implementation

[0041] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0042] Specific Implementation Method 1: This implementation method describes a sandwich-type polyacid-based metal-organic hybrid material, wherein the molecular formula of the hybrid material is C0. 24 H 148 Cu4P 127 Mo 24 N 24 O 127 Its basic structural unit contains {Cu4[(Mo6O]} 12 [OH)3]4}{PO4}4{HPO4} 12It is composed of a single unit cell, protonated ethylenediamine, protonated water, and lattice water, and contains four different crystallographic copper ions. Among them, Cu1 ions coordinate with O46, O47, and O50; Cu2 ions coordinate with O10, O11, and O13; Cu3 ions coordinate with O23, O28, and O30; and Cu4 ions coordinate with O37, O40, and O43, forming {Cu[(Mo6O]... 12 (OH)3]4}{PO4}{HPO4}4 units, forming Cu[Mo6P4O in two-dimensional space. 31 ]2. The sandwich-shaped structure, together with water molecules and ethylenediamine molecules, constitutes a sandwich-shaped polyacid-based metal-organic hybrid material.

[0043] Specific Implementation Method Two: The preparation method of the Meiji sandwich-type multi-acid-based metal-organic hybrid material electrolytic water evolution hydrogen electrode material in this embodiment is completed according to the following steps:

[0044] 1. Preparation of reaction solution with pH value of 4~4.5: Add appropriate amounts of sodium molybdate, copper sulfate, ethylenediaminetetraacetic acid and phosphoric acid to distilled water and stir evenly. Then adjust the pH value to 4~4.5 to obtain a reaction solution with pH value of 4~4.5.

[0045] The molar ratio of sodium molybdate to copper sulfate mentioned in step one is (0.25-0.3):(0.25-0.35).

[0046] The molar ratio of sodium molybdate to ethylenediaminetetraacetic acid mentioned in step one is (0.25-0.3):(0.6-0.7).

[0047] The volume ratio of sodium molybdate to phosphoric acid in step one is (0.25-0.3) mmol: (1-3) mL;

[0048] The molar ratio of sodium molybdate to distilled water in step one is (0.25-0.3) mmol: (10-15) mL;

[0049] 2. The reaction solution with a pH of 4-4.5 prepared in step 1 is transferred to a polytetrafluoroethylene reactor and reacted at 160℃ for 4 days. After the reaction solution is cooled to room temperature, it is washed to obtain reddish-brown blocky crystals, which is a sandwich-type polyacid-based organometallic hybrid material. The chemical formula of this hybrid material is (C2H4N2H6). 12 {Cu2[Mo6O 12 (OH)3]4}{PO4}8{HPO4}8·2H3O·H2O, wherein C2H4N2H6 is ethylenediamine; the crystals are reddish-brown and massive in appearance; the crystal system is triclinic; the space group is […]. P -1; cell parameters are a =13.4175(6) Å,b =23.9015(10) Å, c =26.8323(12) Å, α=111.9630(10)°, β=103.5640(10)°, γ=93.1980(10)°, V =7659.1(6) Å 3 ;

[0050] III. Method for preparing a sandwich-type polyacid-based metal-organic hybrid material for hydrogen evolution by water electrolysis: 100 mg of the material prepared in Example 1 and 100 mg of thiourea were mixed evenly and dissolved in 30 mL of distilled water. The mixture was stirred thoroughly for 60 min. The reaction solution was then transferred to a 50 mL polytetrafluoroethylene reactor and reacted at 200 °C for 24 h. After the temperature of the reaction solution was lowered to room temperature, it was washed to obtain a black bimetallic sulfide crystalline material Cu2S-MoS2.

[0051] In step three, the sandwich-type polyacid-based metal-organic hybrid material needs to be ground in an agate mortar for 1 hour before use.

[0052] IV. 5 mg of bimetallic sulfide Cu2S-MoS2 crystalline material was dissolved in 375 mL of distilled water, 125 mL of ethanol, and 10 μL of Nafion solution to prepare a slurry. The slurry was ultrasonicated for 2 h to obtain a uniformly dispersed mixture. 10 μL of this mixture was drop-coated onto both sides of a pre-weighed, pre-treated carbon cloth (0.0323 g), and dried at room temperature to obtain the working electrode Cu2S-MoS2@CC, used for electrochemical testing. The carbon cloth loading was 10 mg.

[0053] In step four, the carbon cloth needs to be ultrasonicated with acetone, ethanol, and distilled water for 30 minutes each, then treated with an appropriate amount of nitric acid in a reaction vessel at 100 degrees Celsius for 2 hours. After cooling to room temperature, it is cleaned with distilled water and dried at 60 degrees Celsius for later use. A Cu2S-MoS2 crystalline material electrode is used as the working electrode, a saturated calomel electrode as the reference electrode, and a carbon rod as the counter electrode.

[0054] Specific Implementation Method 3: A method for preparing a sandwich-type polyacid-based metal-organic hybrid material as described in step 2 of Specific Implementation Method 2, wherein the molar ratio of sodium molybdate, copper sulfate, and ethylenediaminetetraacetic acid is 1:1.04:2.36.

[0055] Specific Implementation Method Four: The difference between this implementation method and Specific Implementation Method Two is that the sodium molybdate, copper sulfate, ethylenediaminetetraacetic acid, phosphoric acid, and distilled water in step one are 0.0686 g, 0.0735 g, 0.1913 g, 2 mL, and 12 mL, respectively. Everything else is the same as in Specific Implementation Methods One to Three.

[0056] Specific Implementation Method Five: The difference between this implementation method and Specific Implementation Method Two is that the pH value of the reaction solution in step one is adjusted to 4-4.5 using ethylenediamine solution. The other steps are the same as in Specific Implementation Methods One through Four.

[0057] Specific Implementation Method Six: The difference between this implementation method and Specific Implementation Method Two is that the reaction temperature in step one is 140~160℃, and the time is 3~5 days. The other steps are the same as in Specific Implementation Methods One through Five.

[0058] Specific Implementation Method Seven: The mass ratio of the sandwich-type polyacid-based organometallic hybrid material and thiourea to the volume of distilled water prepared in step three of Specific Implementation Method One is 0.1 g:0.1 g:30 mL.

[0059] Specific Implementation Method 8: The volume ratio of the sandwich-type polyacid-based metal-organic hybrid material, ethanol, distilled water, and Nafion prepared in step four of Specific Implementation Method 1 is 5 mg: 125 mL: 375 mL: 10 μL.

[0060] The beneficial effects of the present invention are verified using the following embodiments:

[0061] This embodiment describes a method for preparing a sandwich-type multi-acid-based metal-organic hybrid material, which is implemented according to the following steps:

[0062] 1. Preparation of reaction solution with pH value of 4~4.5: Add appropriate amounts of sodium molybdate, copper sulfate, ethylenediaminetetraacetic acid and phosphoric acid to distilled water and stir evenly. Then adjust the pH value to 4~4.5 to obtain a reaction solution with pH value of 4~4.5.

[0063] The molar ratio of sodium molybdate to copper sulfate mentioned in step one is (0.25-0.3):(0.25-0.35).

[0064] The molar ratio of sodium molybdate to ethylenediaminetetraacetic acid mentioned in step one is (0.25-0.3):(0.6-0.7).

[0065] The volume ratio of sodium molybdate to phosphoric acid in step one is (0.25-0.3) mmol: (1-3) mL;

[0066] The molar ratio of sodium molybdate to distilled water in step one is (0.25-0.3) mmol: (10-15) mL;

[0067] 2. The reaction solution with a pH of 4-4.5 prepared in step 1 is transferred to a polytetrafluoroethylene reactor and reacted at 160°C for 4 days. After the temperature of the reaction solution drops to room temperature, it is washed to obtain reddish-brown blocky crystals, which is a sandwich-type polyacid-based metal-organic hybrid material.

[0068] (a) Structural determination of a sandwich-type polyacid-based metal-organic hybrid material prepared in this embodiment:

[0069] Conclusion ① X-ray crystallographic parameters: see Table 1.

[0070] Table 1 Crystal Data

[0071] Chemical formula <![CDATA[C 24 A 148 Cu4P 127 Mo 24 N 24 O 127 ]]> molecular weight 5857.64 Crystal system Triclinic Space Group P-1 a / Å 13.4175(6) b / Å 23.9015(10) c / Å 26.8323(12) α / deg 111.9630(10) β / deg 103.5640(10) γ / deg 93.1980(10) <![CDATA[V / Å 3 ]]> 7659.1(6) Z 2 <![CDATA[D calcd / g cm −3 ]]> 2.42 T / K 293(2) Refl. Unique 26717 <![CDATA[R int ]]> 0.0334 <![CDATA[GOF on F 2 ]]> 1.003 <![CDATA[R1 / wR2[I>2 σ(I)] a, b ]]> 0.0838 / 0.2673

[0072] a R 1 = ∑║ F o │-│ F c ║ / ∑│ F o │, b wR 2 = {∑[ w ( F o 2 - F c 2 ) 2 ] / ∑[ w ( F o 2 ) 2 ]} 1 / 2

[0073] Conclusion ② X-ray crystal structure description: X-ray single-crystal diffraction analysis shows that the sandwich-type polyacid-based metal-organic hybrid material is triclinic. P -1 space group. Its basic structural unit contains four copper ions and four [Mo6O] ions. 12 [OH)3]4}{PO4}8{HPO4}8 unit, one water molecule, two protonated water molecules, and twelve ethylenediamine molecules, wherein copper ions and [Mo6O 12 Oxygen atoms coordinate in the (OH)3]4}{PO4}8{HPO4}8 unit to form Cu[Mo6P4O 31 ]unit( Figure 1 Copper connects two symmetrical [Mo6P4O] atoms 31 The unit forms a sandwich-shaped Cu[Mo6P4O] unit.31 The structure has two orientations of Cu[Mo6P4O]2. 31 ]2 structures, which exhibit a relative relationship ( Figure 2 Hydrogen bonds are mainly formed in ethylenediamine molecules, water molecules, and four [Mo6O] molecules. 12 In the oxygen of the (OH)3]4}{PO4}8{HPO4}8 unit, specifically the hydrogen atom and water molecule on N16, oxygen O5W, Cu1[Mo6P4O 23 In ]2, O2O1 forms an O…H–N hydrogen bond, and the hydrogen atom on N7 and Cu1[Mo6P4O 23 ]2O98, Cu2[Mo6P4O 23 In ]2, O76 forms an O…H–N hydrogen bond, and the hydrogen atom on N17 forms a Cu1[Mo6P4O] bond. 23 In 2, O48, O94, Cu2[Mo6P4O] 23 In ]2, O76 forms an O…H–N hydrogen bond, and the hydrogen atom on N1 and Cu1[Mo6P4O 23 ]2 O103, Cu3[Mo6P4O 23 In [2], O26, O29, and O69 form O…H–N hydrogen bonds; hydrogen atoms on N3 and oxygen in O1W form O…H–N hydrogen bonds; hydrogen atoms on N13 and Cu4[Mo6P4O] 23 In 2, O42 forms an O…H–N hydrogen bond, and hydrogen atoms on N14 form Cu3[Mo6P4O 23 In ]2, O72 forms an O…H–N hydrogen bond, and hydrogen atoms on N26 are Cu4[Mo6P4O 23 In ]2, O87 forms an O…H–N hydrogen bond, and hydrogen atoms on N22 are Cu3[Mo6P4O 31 In ]2, O32 forms an O…H–N hydrogen bond, and hydrogen atoms on N21 are Cu4[Mo6P4O 23 In ]2, O124 and O3W form O…H–N hydrogen bonds ( Figure 3 These basic units are arranged in an alternating pattern in space. In this diagram, the bright blue octahedrons represent copper, the dark blue octahedrons represent molybdenum, and the pink tetrahedrons represent phosphorus. Through hydrogen bonding, each layer consists of Cu[Mo6P4O] in one direction. 31 Ultimately, a sandwich-type polyacid-based metal-organic hybrid material is formed through two-dimensional hydrogen bond connections. Figure 4 ), Figure 5 This is an atomic structure diagram of hydrogen-bonded structures in a sandwich-type polyacid-based metal-organic hybrid material.

[0074] Figure 1 Cu[Mo6P4O] is a sandwich-type multi-acid-based organometallic hybrid material. 23 ]2 Dimer structure;

[0075] Figure 2 Two-dimensional structural diagram of sandwich-type polyacid-based metal-organic hybrid material;

[0076] Figure 3 A schematic diagram of hydrogen bond formation in a unit cell of a sandwich-type polyacid-based metal-organic hybrid material;

[0077] Figure 4 This is a schematic diagram of hydrogen bond formation in the two-dimensional structure of a sandwich-type multi-acid-based metal-organic hybrid material; the sky-blue octahedron is copper, the dark blue octahedron is molybdenum, and the pink tetrahedron is phosphorus.

[0078] Figure 5 A schematic diagram of hydrogen bond formation in the two-dimensional structure of sandwich-type polyacid-based metal-organic hybrid materials;

[0079] (ii) The molecular formula of the sandwich-type polyacid-based metal-organic hybrid material prepared in Example 1 is (C2H4N2H6). 12 {Cu4[Mo6O 12 Infrared spectroscopy characterization was performed on [OH)3]4}{PO4}8{HPO4}8·2H3O·H2O to obtain the infrared spectrum of this polyacid-based organometallic hybrid material, as shown below. Figure 6 As shown. This infrared spectrum indicates that at 3326 cm⁻¹... -1 3400 cm -1 The peak is the stretching vibration peak of the OH group of water molecules, at 1650 cm⁻¹. -1 The peak is the OH bending vibration peak of the water molecule, at 1537 cm⁻¹. -1 The peak is the NH absorption vibration peak, 1066 cm⁻¹. -1 The absorption vibration frequency of PO is 940 cm⁻¹. -1 for Mo-O d The absorbed vibration frequency is 736 cm. -1 The absorption vibration frequency of Mo-O-Mo is 670 cm⁻¹. -1 for Mo-O a - The absorption vibration frequency of Cu is 895 cm⁻¹. -1 for Mo-O b -Mo's absorbed vibrational frequency.

[0080] Figure 6 The infrared spectrum of a sandwich-type polyacid-based metal-organic hybrid material is shown in the example.

[0081] (III) Powder X-ray diffraction was performed on Cu2S-MoS2@CC, a bimetallic sulfide derived from a sandwich-type polyacid-based organometallic hybrid material prepared in Example 1. The prepared Cu2S-MoS2@CC material was compared with the standard card of MoS2 (JCPDS No. 17-0744) and the standard card of Cu2S (JCPDS No. 46-1195). The strong diffraction peak at 2θ=14.2° corresponds to the characteristic peak of the (002) crystal plane of molybdenum disulfide, while the peaks at 33.5°, 39.8°, and 59.1° correspond to the (100), (103), and (110) crystal planes of molybdenum disulfide, respectively. The peaks at 2θ=26.1°, 37.2°, 45.7°, and 48.1° correspond to the (211), (204), (630), and (136) crystal planes of Cu2S, respectively. The prepared sample matches well with the standard cards of MoS2 and Cu2S, confirming that the obtained material is Cu2S-MoS2@CC.

[0082] Figure 7 Example 1: X-ray powder diffraction pattern of Cu2S-MoS2@CC, a bimetallic sulfide derived from a sandwich-type polyacid-based metal-organic hybrid material.

[0083] (iv) X-ray photoelectron spectroscopy (XPS) was performed on the bimetallic sulfide Cu2S-MoS2@CC derived from the sandwich-type polyacid-based organometallic hybrid material prepared in Example 1. The results are as follows: Figure 8 As shown in the figure, the characteristic peaks of S2p, Cu2p and Mo3d are displayed. Figure 8 (a) It can be seen that the characteristic peaks of Cu 2p appear at 932.8 eV and 952.5 eV, and these two peak positions are respectively attributed to Cu + 2p 3 / 2 and Cu + 2p 1 / 2 . Figure 8 In (b), the characteristic peaks of S 2p appear at 162.0 eV and 163.2 eV, which are attributed to S 2p. 3 / 2 and S 2p 1 / 2 This is caused by the Mo-S bonds in MoS2. Figure 8 In (c), the characteristic peaks of Mo 3d appear at 229.3 eV and 235.1 eV, which are attributed to the Mo 3d corresponding to Mo(VI) of MoS2. 5 / 2 and Mo 3d 3 / 2 The bimodal peaks, 231.8 and 234.7 eV, belong to the Mo(IV) oxidase corresponding to Mo3d in MoS2. 5 / 2 and Mo 3d 3 / 2The spectrum is bimodal. The relatively smaller peak at 226.5 eV belongs to the S 2s spectrum. Figure 8 (d) shows the characteristic peaks in the XPS full spectrum of the sample, proving that the material contains copper, molybdenum and sulfur, while the carbon may have come from the air.

[0084] Figure 8 The image shows the X-ray photoelectron spectroscopy (XPS) spectrum of Cu2S-MoS2@CC obtained in Example 1; (a) represents Cu2p, (b) represents S2p, (c) represents Mo3d, and (d) is the full XPS spectrum.

[0085] (v) Scanning electron microscopy (SEM) was performed on the bimetallic sulfide Cu2S-MoS2@CC derived from the sandwich-type polyacid-based metal-organic hybrid material prepared in Example 1. The results are as follows: Figure 9 As shown, by Figure 9 (a) and (b) at different magnifications show that Cu₂S-MoS₂@CC is a nanosphere structure with regular morphology and uniform size on carbon cloth. (c) and (d) are the electron spectra of Cu₂S-MoS₂@CC. The spectra show that the material mainly contains Mo, Cu, and S elements, which are uniformly distributed on the material. Combined with X-ray powder diffraction, the chemical composition of the nanosphere structure can be further determined to be MoS₂ and Cu₂S.

[0086] Figure 9 The images show scanning electron microscope (SEM) and electronic energy dispersive spectroscopy (EDS) images of Cu2S-MoS2@CC obtained in Example 1; (a)-(b) are images of Cu2S-MoS2@CC electrode material at different magnifications; (c), (d), (e), and (f) are surface scan images of selected regions and S, Mo, and Cu electronic energy dispersive spectroscopy images.

[0087] (vi) Electrolysis of water to produce hydrogen was performed on Cu2S-MoS2@CC, a bimetallic sulfide derived from a sandwich-type polyacid-based organometallic hybrid material prepared in Example 1. A CHI 760E workstation was used in a conventional three-electrode system to test the material's cyclic voltammetry (CV), linear sweep voltammetry (LSV), current density versus time (It) curves, electrochemical active surface area (ECSA), and electrochemical impedance spectroscopy. The Cu2S-MoS2@CC electrode was used as the working electrode in the electrochemical experiments, and a saturated calomel electrode (SCE) was used as the reference electrode. A graphite rod was used as the counter electrode. All final potentials were expressed by the Nernst equation as reversible hydrogen electrode (RHE): in 0.5 mol / L H2SO4 solution, E RHE = E SCEThe linear sweep voltammetry (LSV) was performed at a range of 0 to -1.0 V, with a scan rate of 5 mV·s. The initial voltage was +0.245 V. -1 Hydrogen bubbles formed on the catalyst surface were removed using a stable nitrogen gas flow. Stability was determined by continuous electrolysis of water to produce hydrogen over 24 hours using current-time curves. All current densities were calculated as the ratio of current to the geometric area of ​​the working electrode.

[0088] The Cu2S-MoS2@CC bimetallic sulfide crystalline material prepared in Example 1 was used as an electrode in a 0.5 M H2SO4 solution for water electrolysis hydrogen evolution test. The water electrolysis hydrogen evolution effect is as follows: Figure 10 As shown, by Figure 10 (a) is a comparison of the overpotentials of Cu2S-MoS2@CC material and carbon cloth, which shows that at a current density of 10 mA / cm²... 2 The overpotential of the Cu2S-MoS2@CC material before activation was 87 mV, while that of the bare carbon cloth was 400 mV. This indicates that the material has a certain improvement effect on hydrogen evolution in water electrolysis. This is mainly because MoS2 has a graphene-like layered structure with a large number of active sites at the layer edges. After the introduction of Cu2S, the synergistic effect of the bimetallic sulfide makes the hydrogen evolution performance higher than that of molybdenum disulfide, and it has better catalytic performance for hydrogen production in water electrolysis. Figure 10 (b) is a comparison of the Tafel slopes of Cu2S-MoS2@CC material and carbon cloth. The Tafel slope of Cu2S-MoS2@CC material is 31.9 mV dec. -1 The Tafel slope of the carbon cloth is 66.14 mV dec. -1 Generally speaking, the smaller the Tafel slope, the better the hydrogen production effect of the material through water electrolysis. Figure 10 (c) is the cyclic voltammogram of the Cu2S-MoS2@CC material. Based on the measured range of -0.635V to 0.595V, the algebraic sum of the currents corresponding to the midpoint voltage value is used as the ordinate, and different scan rates are used as the abscissa to obtain the double-layer capacitance of the material, which is proportional to the electrochemically active area. Figure 10 (d) The electrochemical active area of ​​the Cu2S-MoS2@CC material is 83.28 mF / cm². 2 The electrochemically active area of ​​the bare carbon cloth is 15.5 mF / cm². 2 The larger the electrochemical active area, the more active sites the material has, and the better the hydrogen evolution effect of water electrolysis.

[0089] Figure 10Characterization diagrams of the hydrogen evolution performance of Cu2S-MoS2@CC and carbon cloth in water electrolysis obtained in Example 1; (a) Comparison of overpotential between Cu2S-MoS2@CC and carbon cloth, (b) Comparison of Tafel slope between Cu2S-MoS2@CC and carbon cloth, (c) Cyclic voltammetry diagram of Cu2S-MoS2@CC, (d) Comparison of electrochemical active area between Cu2S-MoS2@CC and carbon cloth;

[0090] (vii) The bimetallic sulfide Cu2S-MoS2@CC derived from the sandwich-type polyacid-based metal-organic hybrid material prepared in Example 1 was subjected to AC impedance, current-time stability, and cyclic voltammetry tests. Figure 11 (a) is an AC impedance test. The diameter of the semicircle in the high-frequency region represents the transfer resistance of the catalyst, and the slope of the straight line in the low-frequency region represents the internal resistance of the material. The simulation results obtained by ZView software show that the transfer resistance and internal resistance of Cu2S-MoS2@CC material are 1.33 Ω and 0.42 Ω, respectively, which are lower than the transfer resistance of carbon cloth (2.12 Ω) and internal resistance (0.48 Ω). This indicates that the internal charge transfer of Cu2S-MoS2@CC catalyst is faster, and the hydrogen production performance of Cu2S-MoS2@CC by water electrolysis is better than that of carbon cloth. Figure 11 (b) is the water electrolysis stability test of the material. The chronopotential method is used, that is, the change of potential over time is measured. The curve of the material continuously evolving hydrogen for 24 hours has basically no change, indicating that the material has excellent electrochemical stability. Figure 11 (c) is the cyclic voltammogram of the carbon cloth at different scan rates. Figure 11 (d) shows the stability test of carbon cloth in water electrolysis. During the continuous hydrogen evolution for 24 hours, there was some shaking, indicating poor stability.

[0091] Figure 11 The figures are: 11(a) Comparison of Cu2S-MoS2@CC and carbon cloth electrolysis for hydrogen evolution in Example 1; 11(a) Comparison of AC impedance of Cu2S-MoS2@CC and carbon cloth (interspersed with equivalent circuit diagram and enlarged AC impedance diagram in the high-frequency region); 11(b) Current-time stability diagram of Cu2S-MoS2@CC; 11(c) Cyclic voltammetry diagram of carbon cloth; 11(d) Current-time stability diagram of carbon cloth.

[0092] In summary, the sandwich-type polyacid-based metal-organic hybrid material of this embodiment was successfully prepared by hydrothermal synthesis and used to prepare an electrolytic hydrogen evolution electrode material for water electrolysis. This material has a low overpotential, a small Tafel, a large electrochemical active area, excellent conductivity and stability, and is a high-performance electrolytic hydrogen evolution electrode material for water electrolysis, which also shows potential application value in the field of hydrogen energy development.

Claims

1. A sandwich-type polyacid-based metal-organic hybrid material with the molecular formula (C2H4N2H6). 12 {Cu4[Mo6O 12 (OH)3]4}{PO4}8{HPO4}8·2H3O·H2O, wherein C2H4N2H6 is ethylenediamine, the crystals are reddish-brown lumps; the crystal system is triclinic; the space group is P -1; cell parameters are a =13.4175(6) Å, b =23.9015(10) Å, c =26.8323(12)Å, α=111.9630(10)°, β=103.5640(10)°, γ=93.1980(10)°, V =7659.1(6) Å 3 .

2. A method for preparing a sandwich-type polyoxometalate-based metal-organic hybrid material, which is completed according to the following steps: I. Preparing a reaction solution with a pH value of 4-4.5: a proper amount of sodium molybdate, copper sulfate, ethylenediaminetetraacetic acid and phosphoric acid are added to distilled water and stirred uniformly, and then the pH value is adjusted to 4-4.5 to obtain a reaction solution with a pH value of 4-4.5; The molar ratio of sodium molybdate to copper sulfate in step I is (0.25-0.3):(0.25-0.35); The molar ratio of sodium molybdate to ethylenediaminetetraacetic acid in step I is (0.25-0.3):(0.6-0.7); The volume ratio of the amount of substance of sodium molybdate to phosphoric acid in step I is (0.25-0.3) mmol:(1-3) mL; The volume ratio of the amount of substance of sodium molybdate to distilled water in step I is (0.25-0.3) mmol:(10-15) mL; II. The reaction solution with pH value of 4-4.5 prepared in step I is transferred into a polytetrafluoroethylene reaction kettle, and reacted at a temperature of 160°C for 4 days. After the temperature of the reaction solution is reduced to room temperature, it is washed to obtain red-brown block crystals, i.e. a sandwich type polyoxometallic metal-organic hybrid material, and the chemical formula of the hybrid material is (C2H4N2H6) 12 {Cu4[Mo6O 12 (OH)3]4}{PO4}8{HPO4}8·2H3O·H2O, wherein C2H4N2H6 is ethylenediamine; the crystal appearance is red-brown block, respectively; the crystal system is triclinic; the space group is P -1; the unit cell parameters are a =13.4175(6) Å, b =23.9015(10) Å, c =26.8323(12) Å, α=111.9630(10)°, β=103.5640(10)°, γ=93.1980(10)°, V =7659.1(6) Å 3 .

3. The method for preparing a sandwich-type polyacid-based metal-organic hybrid material according to claim 2, characterized in that, The molar ratio of sodium molybdate, copper sulfate and ethylenediaminetetraacetic acid in step I is 1:1.04:2.

36.

4. The method for preparing a sandwich-type polyacid-based metal-organic hybrid material according to claim 2, characterized in that, The amounts of sodium molybdate, copper sulfate, ethylenediaminetetraacetic acid, phosphoric acid and distilled water in step I are 0.0686 g, 0.0735 g, 0.1913 g, 2 mL and 12 mL, respectively.

5. The method for preparing a sandwich-type three-dimensional polyacid-based metal-organic hybrid material according to claim 2, characterized in that, The process of adjusting the pH value of the reaction solution to 4-4.5 in step I is adjusted using an ethylenediamine solution.

6. A method for preparing an electrolytic water hydrogen evolution working electrode of a sandwich-type two-dimensional polyoxometalate-based metal-organic hybrid material: 100 mg of the hybrid material of claim 1 and 100 mg of thiourea are mixed uniformly and dissolved in 30 mL of distilled water, and stirred fully for 60 min, and then the reaction solution is transferred into a 50 mL polytetrafluoroethylene reactor, and reacted at a temperature of 200 ℃ for 24 h, and then the reaction solution is washed after the temperature is reduced to room temperature to obtain black bimetallic sulfide crystalline material Cu2S-MoS2; 5 mg of the bimetallic sulfide Cu2S-MoS2 crystalline material is dissolved in 375 mL of distilled water, 125 mL of ethanol and 10 μL of a Nafion solution to prepare a slurry, and the slurry is ultrasonically treated for 2 h to obtain a uniformly dispersed mixture, and 10 μL of the mixture is dropped and coated on both sides of a previously weighed and treated carbon cloth, and dried at room temperature to obtain a working electrode Cu2S-MoS2@CC, which is used for electrochemical testing, and the carbon cloth loading is 10 mg.

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