Carbon cloth supported amorphous MOF electrocatalyst and preparation method and application thereof

Abstract

The application discloses a carbon cloth loaded amorphous MOF electrocatalyst and a preparation method and application thereof, and comprises the following steps: (1) adding cetyltrimethylammonium bromide, a metal salt and a ligand in a mixture of N,N-dimethylformamide and water, and using the mixture after ultrasonic dissolution as an electrolyte; (2) using carbon cloth as a working electrode, a carbon rod as a counter electrode and saturated potassium chloride filled Ag / AgCl as a reference electrode in the electrolyte with a proper proportion, and promoting the rapid deposition of MOF on the carbon cloth under a constant potential. The prepared catalyst has rich active sites and high electron conductivity, and exhibits excellent electrocatalytic hydrazine oxidation performance and good stability.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial synthesis technology, specifically to a carbon cloth-supported amorphous MOF electrocatalyst, its preparation method, and its application. Background Technology

[0002] Metal-organic frameworks (MOFs) are a class of crystalline porous materials with a periodic network structure, formed by the self-assembly of inorganic metal centers (metal ions or clusters) and bridging organic ligands. The high crystallinity of MOFs gives them strong stability in catalytic reactions, demonstrating great potential as novel electrocatalysts. However, the high crystallinity of MOFs is also a double-edged sword. Most of the metal active sites are completely embedded in the crystal framework, making it difficult for the reaction substrate to enter the framework. Furthermore, the ionic bonds between the metal centers and organic ligands lead to large band gaps and closed electronic states, thereby reducing the conductivity of the catalyst and hindering the electrochemical reaction process.

[0003] Introducing defect sites into MOFs holds promise for exposing more catalytically active sites and thus enhancing reactivity. Studies have shown that chemical bonds can be broken and defects introduced into MOFs through methods such as high-temperature calcination and acid-base etching. However, these methods require stringent experimental conditions and are prone to framework collapse. Defective MOFs can be directly synthesized using mixed organic ligands or metal centers, but this method is only applicable to specific types of MOFs, limiting its application. Furthermore, during electrocatalysis, MOFs need to be bonded to a conductive substrate using binders, leading to blockage of reactive sites. Therefore, a simple method is urgently needed to synthesize defective MOF electrocatalysts with abundant active sites and high conductivity. Summary of the Invention

[0004] Objective of the invention: To address the problems of low active site exposure and poor conductivity in highly crystalline MOF materials, a carbon cloth-supported amorphous MOF electrocatalyst, its preparation method, and its application are provided.

[0005] The specific solution provided by this invention is: a method for preparing amorphous MOF electrocatalyst supported on carbon cloth, comprising the following steps:

[0006] (1) Add hexadecyltrimethylammonium bromide (CTAB), metal salt and ligand to N,N-dimethylformamide (DMF) or a mixture of N,N-dimethylformamide and water, and use it as an electrolyte after ultrasonic dissolution;

[0007] (2) In a properly prepared electrolyte, carbon cloth (CC) is used as the working electrode, a carbon rod is used as the counter electrode, and Ag / AgCl filled with saturated potassium chloride is used as the reference electrode. Under constant potential, MOF is rapidly deposited on the carbon cloth to generate amorphous MOF electrocatalyst supported on carbon cloth.

[0008] Furthermore, the volume ratio of DMF to water in step (1) is 1:0 to 1.

[0009] Furthermore, the metal salt mentioned in step (1) is a manganese nitrate, and the ligand is 1,1'-ferrocene dicarboxylic acid (Fc').

[0010] Furthermore, the molar concentration of the metal salt in step (1) is 0.004 to 1 mol / L; the molar concentration of the ligand is 0.005 to 0.5 mol / L; the molar concentration of CTAB is 0 to 0.1 mol / L, without zero values; the addition of CTAB can regulate the morphology of the electrocatalyst.

[0011] Furthermore, the carbon cloth is pretreated as follows: soaked in acid for a period of time, cleaned with solvent, and then vacuum dried; the acid is nitric acid and / or sulfuric acid, and the solvent is one or more of methanol, ethanol, and deionized water; the acid can remove any grease and deposits that may be present on the carbon cloth.

[0012] Furthermore, the CC is immersed in acid for 0–48 hours without zero values, and vacuum dried for 0–48 hours without zero values.

[0013] Furthermore, the constant potential in step (2) is -2.0 to -1.2V; the electrodeposition time is 0 to 60 min, excluding 0 values.

[0014] Furthermore, it also includes the step of washing the carbon cloth-supported amorphous MOF electrocatalyst with a washing solvent and then vacuum drying it; the washing solvent is one or more of methanol, ethanol, and deionized water.

[0015] Amorphous MOF electrocatalysts supported on carbon cloth were prepared according to the above preparation method.

[0016] Application of the carbon cloth-supported amorphous MOF electrocatalyst in the hydrazine oxidation reaction (HzOR).

[0017] Compared with existing technologies, the technical effects that this invention can achieve include:

[0018] 1) This invention directly constructs an amorphous MOF electrocatalyst on CC by electrosynthesis. The catalyst has an unsaturated long-range disordered structure, exposing more catalytic active centers and significantly improving electrochemical reaction performance.

[0019] 2) The amorphous MOF electrocatalyst prepared by this invention has excellent electrocatalytic performance for hydrazine oxidation, and its HzOR onset potential and working potential are superior to those of the corresponding crystalline catalysts. Attached Figure Description

[0020] Figure 1 Scanning electron microscope images of aMnFc' / CC prepared at different electrodeposition times in Examples 1-3;

[0021] Figure 2 Transmission electron microscopy (TEM) image and selected area electron diffraction (SED) pattern of aMnFc' scraped off from aMnFc' / CC prepared in Example 3;

[0022] Figure 3 Electron paramagnetic resonance spectra of aMnFc' scraped off from aMnFc' / CC prepared in Example 3 and cMnFc' scraped off from cMnFc' / CC prepared in Comparative Example 5.

[0023] Figure 4 Scanning electron microscope image of aMnFc' / CC prepared for Comparative Example 1;

[0024] Figure 5 Scanning electron microscope image of aNiFc' / CC prepared for Comparative Example 2;

[0025] Figure 6 Scanning electron microscope image of aCoFc' / CC prepared for Comparative Example 3;

[0026] Figure 7 Scanning electron microscope image of aCuFc' / CC prepared for Comparative Example 4;

[0027] Figure 8 (a) Scanning electron microscope image, (b) Scanning electron microscope image, (c) Transmission electron microscope image and selected area electron diffraction pattern of cMnFc' scraped off from cMnFc' / CC prepared in Comparative Example 5.

[0028] Figure 9 The LSV performance curves at different hydrazine concentrations are shown when the aMnFc' / CC prepared in Example 3 is used as the catalyst.

[0029] Figure 10 The LSV performance comparison charts are for the catalysts prepared in Example 3 and Comparative Examples 2-5. Detailed Implementation

[0030] The principles and features of the present invention are described below with reference to embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0031] The carbon cloth used in the following examples and comparative examples has the following dimensions: 1×2×3 cm, and is made of cyber electrochemical material.

[0032] Example 1

[0033] 0.8 g CTAB, 0.084 g Mn(NO3)2·6H2O, and 0.092 g Fc' were added to a mixture of 30 mL DMF and 30 mL water, and dissolved by sonication for 15 min, which was then used as the electrolyte. CC was soaked in acid (nitric acid:sulfuric acid = 1:3) for 24 h, then washed with water and ethanol, and finally dried under vacuum for 12 h. In an electrochemical three-electrode system, the treated CC was used as the working electrode, a carbon rod as the counter electrode, and Ag / AgCl filled with saturated potassium chloride as the reference electrode. MOF deposition on CC was induced at a constant potential of -1.5 V for 10 min. After electrosynthesis, the CC working electrode was rinsed with distilled water and ethanol, and then dried under vacuum at 50 °C for 24 h to obtain amorphous Mn-based MOF electrocatalyst supported on carbon cloth (aMnFc' / CC).

[0034] Figure 1 (a) is a scanning electron microscope image of aMnFc' / CC prepared in Example 1.

[0035] Example 2

[0036] The only difference from Example 1 is that the deposition time is 30 min.

[0037] Figure 1 (b) is a scanning electron microscope image of aMnFc' / CC prepared in Example 2.

[0038] Example 3

[0039] The only difference from Example 1 is that the deposition time is 60 min.

[0040] Figure 1 (c) is a scanning electron microscope image of aMnFc' / CC prepared in Example 3.

[0041] Figure 2The images show the transmission electron microscope (TEM) image and selected area electron diffraction (SED) pattern of aMnFc' scraped off the aMnFc' / CC prepared in Example 3. The TEM image shows no lattice fringes and the SED image shows no diffraction rings / lattices, proving that the material has an amorphous structure.

[0042] Figure 3 The electron paramagnetic resonance spectra of aMnFc' scraped off from aMnFc' / CC prepared in Example 3 and cMnFc' scraped off from cMnFc' / CC prepared in Comparative Example 5 show that the signal intensity at g = 2.13 is significantly higher than that of cMnFc', indicating that there are a large number of defects in aMnFc'.

[0043] Comparative Example 1

[0044] The only difference from Example 3 is that CTAB is not added.

[0045] Figure 4 Scanning electron microscope image of aMnFc' / CC prepared for Comparative Example 1.

[0046] Comparative Example 2

[0047] The only difference from Example 3 is that 0.084g Mn(NO3)2·6H2O is replaced with 0.090g Ni(NO3)2·6H2O.

[0048] Figure 5 Scanning electron microscope image of aNiFc' / CC prepared for Comparative Example 2.

[0049] Comparative Example 3

[0050] The only difference from Example 3 is that 0.084g Mn(NO3)2·6H2O is replaced with 0.085g Co(NO3)2·6H2O.

[0051] Figure 6 Scanning electron microscope image of aCoFc' / CC prepared for Comparative Example 3.

[0052] Comparative Example 4

[0053] The only difference from Example 3 is that 0.084g Mn(NO3)2·6H2O is replaced with 0.071g Cu(NO3)2·3H2O.

[0054] Figure 7 Scanning electron microscope image of aCuFc' / CC prepared for Comparative Example 4.

[0055] Comparative Example 5

[0056] Synthesis of crystalline MOF material: 0.27 g Fc' was dissolved in 30 ml DMF, and 0.29 g Mn(NO3)2·6H2O and 0.8 g CTAB were dissolved in deionized water. The Mn(NO3)2·6H2O solution was poured into the Fc' solution, and then CC was added. The mixture was heated in a reactor at 125 °C for 12 h. The collected CC was washed with methanol and dried at 80 °C to obtain cMnFc' / CC.

[0057] Figure 8 (a) and (b) are scanning electron microscope images of cMnFc' / CC prepared in Comparative Example 5;

[0058] Figure 8 (c) in the figure shows the transmission electron microscope (TEM) image and selected area electron diffraction (SED) pattern of cMnFc' scraped off from cMnFc' / CC prepared in Comparative Example 5. The TEM image shows clear lattice fringes, and the SED image shows diffraction rings / lattices, which are characteristics of crystalline materials.

[0059] Application Example 1

[0060] Electrochemical tests were performed using a three-electrode system. The aMnFc / CC, carbon rod, and Ag / AgCl prepared in Example 3 were used as the working electrode, counter electrode, and reference electrode, respectively. Anodic HzOR performance was tested in a 0.1M PBS + N2H4 mixture, with linear sweep voltammetry (LSV) experiments conducted at 5 mV / s. -1 The reaction proceeded at a rate that was not observed. LSV curves showed that, without the addition of N₂H₄, there was no significant anodic reaction current (relative to RHE) in the potential range of 0.0 to 1.0 V. Upon the addition of N₂H₄, the anodic current increased sharply and gradually increased with increasing N₂H₄ concentration from 0.05 M to 0.4 M. Figure 9 The LSV curve of cMnFc' / CC prepared in Comparative Example 5 showed an onset potential of 540 mV (1 mA / cm). -2 The operating potential is 871 mV, and the current density in 1.0 M PBS + 0.4 M N2H4 electrolyte is 10 mA / cm². -2 .

[0061] Figure 9 The LSV performance curves are shown at different hydrazine concentrations when the aMnFc' / CC catalyst prepared in Example 3 is used as the catalyst.

[0062] Figure 10 This is a comparison of the LSV performance of the catalysts prepared in Example 3 and Comparative Examples 2-5. The aMnFc' / CC catalyst prepared in Example 3 exhibits higher activity at 10 mA / cm². -2Under the given conditions, the initial potential was 287 mV and the operating potential was 667 mV. Amorphous MOF electrocatalysts of different metal species also exhibited different activities, with the trend of initial potential being aCoFc' / CC (340 mV) > aNiFc' / CC (502 mV) > aCuFc' / CC (531 mV).

[0063] Although the present invention has been illustrated and described with reference to preferred embodiments, those skilled in the art should understand that various changes and modifications can be made to the present invention without departing from the scope defined by the claims.

Claims

1. A method for preparing amorphous MOF electrocatalyst supported on carbon cloth, characterized in that, Includes the following steps: (1) Add hexadecyltrimethylammonium bromide, metal salt and ligand to N,N-dimethylformamide or a mixture of N,N-dimethylformamide and water, and use it as an electrolyte after ultrasonic dissolution; (2) In the prepared electrolyte, carbon cloth is used as the working electrode, carbon rod is used as the counter electrode, and Ag / AgCl filled with potassium chloride is used as the reference electrode. Under constant potential, MOF is rapidly deposited on carbon cloth to generate carbon cloth supported amorphous MOF electrocatalyst. The metal salt mentioned in step (1) is a manganese nitrate, and the ligand is 1,1'-ferrocenedicarboxylic acid; The constant potential mentioned in step (2) is −2.0 ~ −1.2 V; Electrodeposition time is 0 ~ 60 min, excluding 0 values.

2. The method for preparing amorphous MOF electrocatalyst supported on carbon cloth according to claim 1, characterized in that, The volume ratio of N,N-dimethylformamide to water in step (1) is 1:0 ~ 1.

3. The method for preparing amorphous MOF electrocatalyst supported on carbon cloth according to claim 1, characterized in that, The molar concentration of the metal salt in step (1) is 0.004 ~ 1 mol / L; the molar concentration of the ligand is 0.005 ~ 0.5 mol / L; and the molar concentration of the hexadecyltrimethylammonium bromide is 0 ~ 0.1 mol / L, without any zero value.

4. The method for preparing amorphous MOF electrocatalyst supported on carbon cloth according to claim 1, characterized in that, The carbon cloth is pretreated as follows: it is soaked in an acid solution for a period of time, cleaned with a solvent, and then vacuum dried; the acid solution is nitric acid and / or sulfuric acid, and the solvent is one or more of methanol, ethanol, and deionized water.

5. The method for preparing amorphous MOF electrocatalyst supported on carbon cloth according to claim 4, characterized in that, The carbon cloth is soaked in acid solution for 0 to 48 hours, excluding zero values; the vacuum drying time is 0 to 48 hours, excluding zero values.

6. The method for preparing amorphous MOF electrocatalyst supported on carbon cloth according to claim 1, characterized in that, It also includes the step of washing the carbon cloth-supported amorphous MOF electrocatalyst with a washing solvent and then vacuum drying it; the washing solvent is one or more of methanol, ethanol, and deionized water.

7. The carbon cloth-supported amorphous MOF electrocatalyst prepared by the preparation method according to any one of claims 1-6.

8. The application of the carbon cloth-supported amorphous MOF electrocatalyst according to claim 7 in the hydrazine oxidation reaction.

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