Co-based two-dimensional coordination polymer electrocatalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of electrocatalysis development, in particular to a Co-based two-dimensional coordination polymer electrocatalyst and a preparation method and application thereof. The chemical formula of the Co-based two-dimensional coordination polymer electrocatalyst is {[Co3 (H2O) 4 (5-CMOIA) 2]. 10H2O} n, an X-ray single crystal diffraction test shows that the coordination polymer belongs to a triclinic system and a P-1 space group, and the minimum asymmetric unit of the coordination polymer contains three Co (II) ions, two deprotonated (5-CMOIA) 3-ligands, four coordination water molecules and ten crystal water molecules. The Co-based two-dimensional coordination polymer has relatively high specific surface area and rich active sites, is good in dispersity in a solution, and can be applied to the field of electrocatalysis.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalytic development, and in particular to a Co-based two-dimensional coordination polymer electrocatalyst and a preparation method and application thereof. Background Art

[0002] As global energy demand continues to grow and environmental problems become increasingly severe, the development of efficient and sustainable clean energy technologies has become a top priority. Hydrogen energy is considered an ideal alternative to fossil fuels due to its high energy density and zero carbon emissions. Electrocatalytic water splitting technology decomposes water into hydrogen and oxygen through hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), which is one of the core ways to achieve green hydrogen production. However, the commercial application of this technology is limited by the high cost, low efficiency and insufficient stability of catalysts. At present, precious metal catalysts (such as Pt / C for HER, IrO 2 / RuO 2 Although non-precious metal catalysts have shown excellent performance in OER, their scarcity and high cost restrict their large-scale application. Therefore, the development of efficient, stable and economical non-precious metal catalysts has become a research focus in this field.

[0003] In recent years, metal-organic frameworks (MOFs) and coordination polymers (CPs) have shown great potential in the field of electrocatalysis due to their structural tunability, high specific surface area and abundant active sites. MOFs form a porous framework structure through the orderly assembly of metal nodes and organic ligands, and the catalytic performance can be optimized by regulating the metal type, ligand function and topological structure. As a subclass of MOFs, two-dimensional coordination polymers (2D CPs) have layered structures and in-plane π conjugation characteristics, and are more advantageous in charge transport and active site exposure. Cobalt-based materials have significant advantages in OER due to their rich oxidation states (Co²⁺ / Co³⁺) and moderate oxygen adsorption energy.

[0004] Based on the above analysis, the present invention attempts to synthesize two-dimensional structured CPs using pyridazine derivatives as ligands and metal cobalt ions, and determines their basic structure and properties through targeted modification and characterization of target molecules, and uses an electrochemical workstation to study the electrocatalytic performance of the target coordination polymer. At the same time, the application of two-dimensional structured Co-based coordination polymers in the field of electrocatalysis further expands the application of coordination polymers in the field of electrocatalysis. Summary of the invention

[0005] The present invention provides a Co-based two-dimensional coordination polymer electrocatalyst and a preparation method and application thereof. The Co-based two-dimensional coordination polymer electrocatalyst has a chemical formula of {[Co 3 (H 2 O) 4 (5-CMOIA) 2 ]·10H2 O} n The smallest asymmetric unit contains three Co(II) ions, two deprotonated (5-CMOIA) 3 - ligand, four coordinated water molecules and ten crystal water molecules. Crystal structure analysis shows that along the a-axis, two crystallographically independent Co(II) ions self-assemble through six ligands to form a ring-shaped building unit, and the ring unit is further extended to form a two-dimensional double-layer structure through the ligand bridging effect. In addition, adjacent two-dimensional layered structures are interconnected and continuously extended through intermolecular forces, eventually forming an infinite three-dimensional supramolecular structure, which has good dispersibility in solution and can be applied in the field of electrocatalysis.

[0006] The present invention provides a Co-based two-dimensional coordination polymer electrocatalyst, wherein the chemical formula of the Co-based two-dimensional coordination polymer electrocatalyst is {[Co 3 (H 2 O) 4 (5-CMOIA) 2 ]·10H 2 O} n .

[0007] The present invention provides a method for preparing the above-mentioned Co-based two-dimensional coordination polymer electrocatalyst, comprising the following steps: S1, cobalt salt, H 3 (5-CMOIA) is added to ethanol to obtain a mixed solution, the pH value of the obtained mixed solution is adjusted to 3.1-3.5, and the reaction is carried out at a constant temperature to obtain a reaction product; S2. Cooling the reaction product obtained in S1 to crystallize, and washing, filtering and drying the crystallized product in sequence to obtain a Co-based two-dimensional coordination polymer electrocatalyst.

[0008] According to the method for preparing a Co-based two-dimensional coordination polymer electrocatalyst provided by the present invention, the cobalt salt in S1 is any one of cobalt nitrate, cobalt carbonate and cobalt chloride.

[0009] According to the preparation method of the Co-based two-dimensional coordination polymer electrocatalyst provided by the present invention, the cobalt salt and H 3 The molar ratio of (5-CMOIA) was 0.60 mmol:0.05 mmol, and the amount of ethanol solvent used was 4 mL.

[0010] According to the preparation method of the Co-based two-dimensional coordination polymer electrocatalyst provided by the present invention, the solution for adjusting the pH in S1 is a concentrated nitric acid solution, the concentration of the concentrated nitric acid solution is 8 mol / L, the temperature of the isothermal reaction is 110°C, and the time of the isothermal reaction is 48 h.

[0011] According to the method for preparing a Co-based two-dimensional coordination polymer electrocatalyst provided by the present invention, the filtration in S2 is reduced-pressure filtration, and the drying condition is: constant-temperature drying in an oven at 30° C. for 12 h.

[0012] The present invention also provides an application of the above-mentioned Co-based two-dimensional coordination polymer electrocatalyst, and the Co-based two-dimensional coordination polymer electrocatalyst can be applied to the field of electrocatalysis.

[0013] H 3 (5-CMOIA) is 5-[3-carboxy-5-methyl-4-oxopyridazin-1(4H)-yl]isophthalic acid, wherein H 3 The structural formula of (5-CMOIA) is: .

[0014] The Co-based two-dimensional coordination polymer electrocatalyst prepared by the present invention has a minimum asymmetric unit comprising three Co(II) ions, two deprotonated (5-CMOIA) 3 - ligands, four coordinated water molecules and ten crystal water molecules. Crystal structure analysis shows that along the a-axis, two crystallographically independent Co(II) ions self-assemble through six ligands to form a ring-shaped building unit, and the ring unit is further extended to form a two-dimensional double-layer structure through the ligand bridging effect. In addition, adjacent two-dimensional layered structures are interconnected and continuously extended through intermolecular forces, eventually forming an infinite three-dimensional supramolecular structure.

[0015] The Co-based two-dimensional coordination polymer electrocatalyst crystal of the present invention belongs to the triclinic system and the P-1 space group, and the unit cell parameters are a=7.4977(3) Å, b=8.8160(3) Å, c=16.2749(5) Å, α=92.060(3) °, β=100.916(3) °, γ=105.825(3) °, V=1011.89(6) Å 3 .

[0016] Compared with the prior art, the present invention has the following advantages: 1. The present invention adopts a one-pot solvent thermal reaction method to prepare a divalent cobalt ion coordination polymer, and the preparation method has the advantages of simple process, convenient operation, high yield and good reproducibility.

[0017] 2. The Co-based two-dimensional coordination polymer electrocatalyst of the present invention has good dispersibility in the solution and strong catalytic activity, and can be applied in the field of electrocatalysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a single molecule image of the Co-based two-dimensional coordination polymer prepared in Example 2; Figure 2 is a two-dimensional double-layer structure diagram of the Co-based two-dimensional coordination polymer prepared in Example 2; Figure 3 is a three-dimensional supramolecular structure diagram of the Co-based two-dimensional coordination polymer prepared in Example 2; Figure 4 is the IR graph of the Co-based two-dimensional coordination polymer measured in Example 5; Figure 5 is the XRD pattern of the Co-based two-dimensional coordination polymer measured in Example 5; Figure 6 is a polarization curve diagram of the Co-based two-dimensional coordination polymer measured in Example 5; Figure 7 is a graph of the electrochemically active surface area of ​​the Co-based two-dimensional coordination polymer measured in Example 5; Figure 8 This is the electrochemical impedance diagram of the Co-based two-dimensional coordination polymer measured in Example 5. DETAILED DESCRIPTION

[0019] Example 1 This embodiment provides a H 3 Preparation method of (5-CMOIA).

[0020] S1. Add 25 g of the reactant 5-aminoisophthalic acid to a 250 mL single-mouth bottle, then add 200 mL of anhydrous ethanol, and stir to obtain reaction solution 1; add 25 mL of thionyl chloride dropwise, and the solution gradually becomes clear as thionyl chloride is added, and after a period of dropwise addition, it becomes a white turbid solution. After the dropwise addition is completed, reflux at 80 °C with stirring, react for 5 h, and after cooling to room temperature, a large amount of white solid precipitates, which is concentrated to obtain a white solid crude product; After concentration, add ethyl acetate to dissolve it and adjust the pH of the solution to neutral. Transfer the solution to a separatory funnel and let it stand for separation. Extract the aqueous phase three times, combine the organic phases, and then extract the combined organic phases with water. The aqueous phase flows out from the bottom and the organic phase is poured out from the mouth. Remove water from the separated organic phase, filter it with suction, and concentrate it to obtain white solid 5-aminoisophthalic acid diethyl ester; S2. Add 6 g (0.025 mol) of 5-aminoisophthalic acid diethyl ester to a 500 mL single-necked bottle, then add 100 mL of distilled water and stir. Add 30 mL of 40% concentrated hydrochloric acid dropwise under ice bath, then add NaNO 2 Solution (2.7 g NaNO 2 Dissolve in 50 mL distilled water) and add dropwise to obtain a yellow clear reaction solution 2; S3. Add 13.5 g of sodium acetate to a 1000 mL flask, dissolve it with 100 mL of distilled water, and then add 175 mL of anhydrous ethanol. Stir at 0 °C. After 25 min, add 10 g of ethyl propionyl acetate. Continue stirring for 20 min, then add reaction solution 2 dropwise. The solution gradually turns yellow. As the diazonium salt is added, a bright yellow solid precipitates. After 3 h, the reaction is completed to obtain a yellow turbid reaction solution 3. Filter and wash the filter cake until it is neutral to obtain a bright yellow filter cake. Dry at room temperature to obtain a bright yellow solid diethyl (E)-5-[2-(1-ethoxy-1,3-dioxaalkane-2-ylidene) hydrazide] isophthalate; S4. Add 10.5 g of diethyl (E)-5-[2-(1-ethoxy-1,3-dioxaalkane-2-ylidene) hydrazide] isophthalate to a 500 mL single-necked bottle, add 100 mL of toluene and dissolve by ultrasonication to obtain a yellow clear reaction solution 4. Add 4.3 g of DMF-DMA, the solution color turns dark purple, reflux at 90 °C, monitor by TLC, and the reaction ends after 12 h. Add appropriate amount of CH 2 Cl 2 Dissolve, ultrasonicate to precipitate a white solid, reflux, stir, and stand for 10 h, filter, and wash the filter cake with petroleum ether to obtain a white-yellow solid 5-[3-(ethoxycarbonyl)-5-methyl-4-oxopyrazine-1(4H)-yl]isophthalate; S5. Add 9.5 g of 5-[3-(ethoxycarbonyl)-5-methyl-4-oxopyrazine-1(4H)-yl]isophthalic acid ester and 150 mL of distilled water to a 500 mL single-necked bottle, stir, then add 6.2 g of sodium hydroxide, heat to 60°C, reflux to obtain a reddish brown solution reaction solution 5. The reaction is completed after 3 h, and the solution turns purple-red. Cool to room temperature, add 150 mL of distilled water to the reaction bottle, and adjust the solution pH to 2. Flesh-colored solid 5-[3-carboxy-5-methyl-4-oxopyridazine-1(4H)-yl]isophthalic acid precipitates in the solution. Filter with suction, wash the filter cake until it is neutral, and dry to obtain a flesh-colored powder.

[0021] Example 2 This embodiment provides a method for preparing a Co-based two-dimensional coordination polymer, and the specific steps are as follows: S1, 0.60 mmol of cobalt nitrate hexahydrate, 0.05 mmol of H 3 (5-CMOIA) was added to a glass scintillation vial containing 4 mL of ethanol solvent and mixed evenly to obtain a mixed solution. The pH value of the mixed solution was adjusted to 3.2 with a concentrated nitric acid solution with a concentration of 8 mol / L. The mixed solution was subjected to solvothermal isothermal reaction at 110 °C for 48 h to obtain a reaction product. S2, cooling the reaction product obtained in S1 to crystallize to obtain a crystallization product, washing the crystallization product with deionized water, and then filtering under reduced pressure to obtain purple-red transparent flaky crystals, placing the purple-red transparent flaky crystals in an oven at a temperature of 30°C for 12 h to obtain a Co-based two-dimensional coordination polymer, the chemical formula of the Co-based two-dimensional coordination polymer is {[Co 3 (H 2 O) 4 (5-CMOIA) 2 ]·10H 2 O} n , the yield is about 76.6%.

[0022] The Co-based two-dimensional coordination polymer prepared in this example has a minimum asymmetric unit comprising three Co(II) ions, two deprotonated (5-CMOIA) 3 - ligands, four coordinated water molecules and ten crystal water molecules. Crystal structure analysis shows that along the a-axis, two crystallographically independent Co(II) ions self-assemble through six ligands to form a ring-shaped building unit, and the ring unit is further extended to form a two-dimensional double-layer structure through the ligand bridging effect. In addition, adjacent two-dimensional layered structures are interconnected and continuously extended through intermolecular forces, eventually forming an infinite three-dimensional supramolecular structure.

[0023] Example 3 This embodiment provides a method for preparing a Co-based two-dimensional coordination polymer, and the specific steps are as follows: S1, 0.60 mmol of cobalt carbonate dihydrate, 0.05 mmol of H 3 (5-CMOIA) was added to a glass scintillation vial containing 4 mL of ethanol solvent and mixed evenly to obtain a mixed solution. The pH value of the mixed solution was adjusted to 3.3 with a concentrated nitric acid solution with a concentration of 8 mol / L. The mixed solution was subjected to solvothermal isothermal reaction at 110 °C for 48 h to obtain a reaction product. S2. The reaction product obtained in S1 is cooled and crystallized to obtain a crystallized product. The crystallized product is rinsed with deionized water, and then filtered under reduced pressure to obtain purple-red transparent flaky crystals. The purple-red transparent flaky crystals are placed in an oven at a temperature of 30°C for 12 h to obtain a Co-based two-dimensional coordination polymer with a yield of about 72.4%.

[0024] Example 4 This embodiment provides a method for preparing a Co-based two-dimensional coordination polymer, and the specific steps are as follows: S1, 0.60 mmol of cobalt chloride hexahydrate, 0.05 mmol of H 3(5-CMOIA) was added to a glass scintillation vial containing 4 mL of ethanol solvent and mixed evenly to obtain a mixed solution. The pH value of the mixed solution was adjusted to 3.5 with a concentrated nitric acid solution with a concentration of 8 mol / L. The mixed solution was subjected to solvothermal isothermal reaction at 110 °C for 48 h to obtain a reaction product. S2. The reaction product obtained in S1 is cooled and crystallized to obtain a crystallized product. The crystallized product is rinsed with deionized water, and then filtered under reduced pressure to obtain purple-red transparent flaky crystals. The purple-red transparent flaky crystals are placed in an oven at a temperature of 30°C for 12 h to obtain a Co-based two-dimensional coordination polymer with a yield of about 70.6%.

[0025] Example 5 The Co-based two-dimensional coordination polymer prepared in Example 2 was characterized.

[0026] (1) Crystal structure determination of Co-based two-dimensional coordination polymers A single crystal with a size of 0.170×0.190×0.230 mm was selected under a microscope and X-ray diffraction experiments were carried out at room temperature.

[0027] Diffraction data were collected on a Bruker-ApexП X-ray single crystal diffractometer. Mo-Kα rays (λ = 0.71073 Å) were monochromatized with a graphite monochromator, and diffraction points were collected in ω-2θ scanning mode. All data were corrected by factors and empirical absorption. The crystal structure was solved by a direct method using a program. Hydrogen atoms were determined by difference Fourier synthesis and fixed in the calculated optimal positions. All non-hydrogen atoms and their anisotropic thermal parameters were corrected based on the full-matrix least squares method using the SHELX-97 program. The main crystallographic measurement data of the Co-based two-dimensional coordination polymer are shown in Table 1. The important bond length and bond angle data of the Co-based two-dimensional coordination polymer are shown in Table 2. The minimum asymmetric unit is shown in Table 2. Figure 1 As shown, the two-dimensional double-layer structure of the polymer is observed from the a-axis direction, as Figure 2 As shown, Figure 3 It is a three-dimensional supramolecular structure of coordination polymer Table 1

[0028] Table 2

[0029] In Table 1, a, b and c represent the edge lengths of the crystal in the directions of the three crystal axes, α, β and γ represent the angles between a and b, a and c, and b and c, respectively; Z is the number of molecules contained in the unit cell; the diffraction index range of the limiting factor is (h, k, l); F (000) is the number of electrons in the unit cell; Final R indices [I>2σ (I)] is the residual factor R value for the observable diffraction point; R is the non-weighted consistency factor; R 1 and wR 2 All are weight consistency factors; In the first row of Table 2, Co2 refers to Co atom 2 in the Co-based two-dimensional coordination polymer single crystal, O6#1 refers to the symmetric atom 1 of O atom 6 in the Co-based two-dimensional coordination polymer single crystal, and Co2- O6#1 represents the bond length between Co atom 2 and symmetric atom 1 of O atom 6, which is 2.044±3, with 3 being the standard deviation; O6#1- Co2-O9 represents the bond angle between the symmetric atom 1 of O atom 6, Co atom 2 and O atom 9, and its bond angle is 100.42±13; (2) Infrared (IR) spectrum characterization Figure 4 Co-based two-dimensional coordination polymer and H 3 IR spectrum of (5-CMOIA), KBr pellets were used, and the infrared spectrum of the sample was collected at 4000-500 cm -1 .Depend on Figure 4 It can be seen that the stretching vibration peak of -OH is approximately 3600-3200 cm -1 1700-1514 cm -1 and 1420-1300 cm -1 The strong peak at corresponds to H 3 (5-CMOIA) carboxylate group (-COO - ) vibration.

[0030] (3) Phase purity characterization of Co-based two-dimensional coordination polymers The powder XRD characterization of the Co-based two-dimensional coordination polymer was performed using a Bruker / D8Advance X-ray diffractometer. The results showed that the positions of the diffraction peaks of the experimental values ​​and the simulated values ​​were in good agreement, indicating its reliable phase purity, such as Figure 5 shown.

[0031] (4) Electrocatalytic performance of Co-based two-dimensional coordination polymers In order to evaluate the electrocatalytic performance of Co-based two-dimensional coordination polymers, a three-electrode system consisting of a glassy carbon electrode, a carbon rod, and a saturated calomel electrode was used for testing. Co-based two-dimensional coordination polymer powder was coated on an area of ​​0.7 cm 2The surface of the glassy carbon electrode was tested with 1 mol / L KOH solution as the electrolyte at a scanning speed of 5 mV / s using linear sweep voltammetry (LSV) and the polarization curve was plotted. Figure 6 As shown, the Co-based 2D coordination polymer requires an overpotential of 385 mV to allow 10 mA / cm 2 A series of cyclic voltammetry (CV) tests were performed in the scan rate range of 50-90 mV / s with an interval of 10 mV / s to obtain the linear relationship between the current density difference (Δj / 2) and the scan rate, and the double layer capacitance (C dl ) to estimate the electrochemically active surface area (ECSA), the C dl The magnitude is 19.08 mF / cm 2 ,like Figure 7 In addition, electrochemical impedance spectroscopy (EIS) was used to characterize the kinetics of the interfacial reaction during the OER process. Through this method, the charge transfer resistance (Rct) of the Co-based two-dimensional coordination polymer can be obtained by fitting the Nyquist plot, as shown in Figure 8 This indicates that the coordination polymer has the potential to be used as an electrocatalyst.

[0032] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A Co-based two-dimensional coordination polymer electrocatalyst, characterized in that: The chemical formula of the Co-based two-dimensional coordination polymer electrocatalyst is {[Co3(H2O)4(5-CMOIA)2]·10H2O} n .

2. A method for preparing the Co-based two-dimensional coordination polymer electrocatalyst according to claim 1, characterized in that: The method comprises the following steps: S1, adding cobalt salt and H3(5-CMOIA) to ethanol to obtain a mixed solution, adjusting the pH value of the obtained mixed solution to 3.1-3.5, and reacting at a constant temperature to obtain a reaction product; S2. Cooling the reaction product obtained in S1 to crystallize, and washing, filtering and drying the crystallized product in sequence to obtain a Co-based two-dimensional coordination polymer electrocatalyst.

3. The method for preparing the Co-based two-dimensional coordination polymer electrocatalyst according to claim 2, characterized in that: The cobalt salt in S1 is any one of cobalt nitrate, cobalt carbonate and cobalt chloride.

4. The method for preparing a Co-based two-dimensional coordination polymer electrocatalyst according to claim 2, characterized in that: The molar ratio of the cobalt salt and H3(5-CMOIA) in S1 is 0.60 mmol:0.05 mmol, and the amount of the ethanol solvent is 4 mL.

5. The method for preparing a Co-based two-dimensional coordination polymer electrocatalyst according to claim 2, characterized in that: The solution for adjusting pH in S1 is a concentrated nitric acid solution, the concentration of the concentrated nitric acid solution is 8 mol / L, the temperature of the isothermal reaction is 110° C., and the time of the isothermal reaction is 48 h.

6. The method for preparing a Co-based two-dimensional coordination polymer electrocatalyst according to claim 2, characterized in that: The filtration in S2 is reduced pressure filtration, and the drying condition is: constant temperature drying in an oven at 30°C for 12 h.

7. An application of the Co-based two-dimensional coordination polymer electrocatalyst as claimed in claim 1, characterized in that: The Co-based two-dimensional coordination polymer electrocatalyst can be applied in the field of electrocatalysis.

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