Multi-metal MOF (Metal Organic Framework) bifunctional catalyst as well as preparation method and application thereof

Abstract

The invention discloses a multi-metal MOF bifunctional catalyst and a preparation method and application thereof.The preparation method comprises the steps that ferric nitrate nonahydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate and anti-butadiene acid are dissolved in a DMF solution, a Fex (CoNi)-MOF material is prepared through a one-step hydrothermal method, and the prepared Fex (CoNi)-MOF has excellent HER and OER catalytic activity and can be used for preparing a multi-metal MOF catalyst. The problem that an existing noble metal catalyst cannot be widely applied due to scarce resources and high cost is solved. The medium-entropy metal is low in cost, the prepared Fex (CoNi)-MOF has HER and OER bifunctional catalytic activity and double effects, the cost is further reduced, and the Fex (CoNi)-MOF can replace a noble metal catalyst to be widely applied.

Description

Technical Field

[0001] The present invention relates to the technical field of metal organic framework materials, and in particular to a multi-metal MOF bifunctional catalyst and a preparation method and application thereof. Background Art

[0002] Renewable energy sources provide thousands of times more electricity than the world's fuel needs every day, but are intermittent in nature. Therefore, storing energy obtained from renewable sources is essential to alleviate the global energy crisis. This energy can be stored either in electrochemical energy storage devices, namely batteries and electrochemical capacitors, or in chemical bonds, such as splitting water into hydrogen and oxygen as energy carriers. Therefore, high-performance electrocatalysts are crucial.

[0003] Metal-organic frameworks (MOFs), as an emerging class of ordered crystalline materials, have tailorable topology, functionality, porosity, and electrocatalytic properties, and exhibit excellent properties in energy storage and conversion systems. Although noble metals such as Pt, Ir, and Ru have excellent catalytic activity for water splitting reaction, hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR), the high cost and scarcity of noble metals severely restrict their widespread application. In addition, the energy efficiency of metal-air batteries is mainly determined by the redox reaction of the air cathode, which requires the development of efficient, economical, durable, and earth-abundant bifunctional electrocatalysts for HER and OER. Summary of the invention

[0004] The embodiments of the present application solve the problem that the noble metal catalysts in the prior art are expensive and cannot be widely used by providing a multi-metal MOF bifunctional catalyst and a preparation method and application thereof, and realize the use of a multi-metal medium-entropy metal MOF bifunctional catalyst to improve the efficiency of hydrogen production by electrolysis of water. Due to its low cost and good catalytic activity, it can replace noble metal catalysts for wide application.

[0005] The present application provides a method for preparing a multi-metal MOF bifunctional catalyst, and the specific steps are as follows:

[0006] Step 1: dissolve two or more different metal salts and an organic dibasic acid in N,N-dimethylformamide in a certain proportion, and stir evenly to obtain solution A;

[0007] Step 2: Transfer the solution A obtained in step 1 to a reactor, dry, centrifuge, wash, and then dry to obtain a multi-metal MOF material.

[0008] Preferably, there are three kinds of metal salts in step 1, specifically ferric nitrate nonahydrate, cobalt nitrate hexahydrate and nickel nitrate hexahydrate.

[0009] Preferably, the reaction temperature of the reactor is 100-120° C., and the reaction time is 8-10 h.

[0010] Preferably, the organic dibasic acid is fumaric acid.

[0011] Preferably, the molar mass ratio of the ferric nitrate nonahydrate, the cobalt nitrate hexahydrate and the nickel nitrate hexahydrate is 1 to 3:1:1.

[0012] Preferably, the molar mass ratio of the ferric nitrate nonahydrate, the cobalt nitrate hexahydrate and the nickel nitrate hexahydrate is 2:1:1.

[0013] Preferably, the molar mass ratio of the ferric nitrate nonahydrate, the cobalt nitrate hexahydrate, the nickel nitrate hexahydrate and the fumaric acid is 1-3:1:1:24-40.

[0014] Preferably, the molar mass ratio of the ferric nitrate nonahydrate, the cobalt nitrate hexahydrate, the nickel nitrate hexahydrate and the fumaric acid is 2:1:1:32.

[0015] The present invention also provides a multi-metal MOF bifunctional catalyst prepared by the above preparation method.

[0016] The present invention also provides an application of a multi-metal MOF bifunctional catalyst in a water electrolysis reaction to improve the efficiency of hydrogen production by water electrolysis.

[0017] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0018] 1. The present invention prepares a multi-metal medium entropy metal MOF catalyst Fe x (CoNi)-MOF material, the prepared Fe2(CoNi)-MOF material has excellent HER and OER bifunctional catalytic performance, so it effectively solves the problem that the precious metal catalysts in the existing technology are expensive and cannot be widely used, and realizes the multi-metal medium-entropy metal MOF bifunctional catalyst to improve the efficiency of hydrogen production by electrolysis of water. Due to its low cost and good catalytic activity, it can replace precious metal catalysts for wide application.

[0019] 2. The Fe2(CoNi)-MOF prepared by the technical solution of the present invention has excellent HER and OER dual-functional catalytic activity in long-term water decomposition reactions. Compared with single-functional precious metal catalysts, it is more practical in addition to reducing costs and has potential practical application value.

[0020] 3. The multi-metal synergistic effect significantly enhanced the reaction kinetics of Fe2(CoNi)-MOF, increased the charge density, and reduced the distance from the d-band to the Fermi level. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 For the present application embodiment Fe x XRD pattern of (CoNi)-MOF material;

[0022] Figure 2 For the present application embodiment Fe x (CoNi)-MOF material morphology and structure diagram;

[0023] Figure 3 For Fe in Example 5 of this application x Linear scan curve (LSV) of HER reaction of (CoNi)-MOF@NF;

[0024] Figure 4 For Fe in Example 5 of this application x Tafel slope curve of the HER reaction of (CoNi)-MOF@NF;

[0025] Figure 5 For Fe in Example 5 of this application x Electrochemical impedance spectroscopy (EIS) of the HER reaction of (CoNi)-MOF@NF;

[0026] Figure 6 For Fe in Example 5 of this application x Double layer capacitance (Cdl) diagram of HER reaction of (CoNi)-MOF@NF;

[0027] Figure 7 For Fe in Example 5 of this application x Linear scan curve (LSV) diagram of the OER reaction of (CoNi)-MOF@NF;

[0028] Figure 8 For Fe in Example 5 of this application x Tafel slope curve of the OER reaction of (CoNi)-MOF@NF;

[0029] Fig. 9 For Fe in Example 5 of this application x Electrochemical impedance spectroscopy (EIS) of the OER reaction of (CoNi)-MOF@NF;

[0030] Fig.10 For Fe in Example 5 of this application x Double-layer capacitance (Cdl) diagram of the OER reaction of (CoNi)-MOF@NF. DETAILED DESCRIPTION

[0031] The embodiments of the present application solve the problem that the noble metal catalysts in the prior art are expensive and cannot be widely used by providing a multi-metal MOF bifunctional catalyst and a preparation method and application thereof, and realize the use of a multi-metal medium-entropy metal MOF bifunctional catalyst to improve the efficiency of hydrogen production by electrolysis of water. Due to its low cost and good catalytic activity, it can replace noble metal catalysts for wide application.

[0032] The technical solution in the embodiment of the present application is to prepare a multi-metal MOF catalyst with dual functions, and the overall idea is as follows:

[0033] First synthesis of a trimetallic mesenterotropic metal-organic framework Fe by a one-step hydrothermal route x (CoNi)-MOF, Fe(CoNi)-MOF, Fe2(CoNi)-MOF and Fe3(CoNi)-MOF were prepared respectively, and electrochemical tests were carried out on Fe(CoNi)-MOF, Fe2(CoNi)-MOF and Fe3(CoNi)-MOF materials. The final experimental results showed that Fe2(CoNi)-MOF has excellent HER and OER catalytic activity, can replace precious metal catalysts, and is widely used.

[0034] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0035] Embodiment 1

[0036] Preparation of Fe(CoNi)-MOF materials

[0037] The chemical formula of ferric nitrate nonahydrate is Fe(NO3)3·9H2O, the chemical formula of cobalt nitrate hexahydrate is Co(NO3)2·6H2O, the chemical formula of nickel nitrate hexahydrate is Ni(NO3)2·6H2O, and N,N-dimethylformamide solution is commonly known as DMF solution.

[0038] Step 1: Dissolve 1.67 mmol of Fe(NO3)3·9H2O, 1.67 mmol of Co(NO3)2·6H2O, 1.67 mmol of Ni(NO3)2·6H2O and 40 mmol of trans-butadienoic acid in 50 ml of DMF solution, stir at room temperature for 30 min at a stirring speed of 200 rpm, and stir evenly to obtain solution A.

[0039] Step 2: The solution A obtained above was transferred to a reactor, and then placed in a 120°C oven for reaction for 8 hours. The reactant was centrifuged for 3 minutes at a speed of 8000 rpm, washed once with deionized water, and then washed three times with anhydrous ethanol. The washed solution was placed in a 40°C oven and dried for 8 hours to collect FeCoNi-MOF.

[0040] Embodiment 2

[0041] Preparation of Fe2(CoNi)-MOF materials

[0042] The preparation process of Fe2(CoNi)-MOF is basically the same as the preparation method in Example 1, except that the Fe(NO3)3·9H2O in step 1 is changed from 1.67mmol to 2.5mmol, the Co(NO3)2·6H2O is changed from 1.67mmol to 1.25mmol, and the Ni(NO3)2·6H2O is changed from 1.67mmol to 1.25mmol, to prepare Fe2(CoNi)-MOF.

[0043] Embodiment 3

[0044] Preparation of Fe3(CoNi)-MOF materials

[0045] The preparation process of Fe3(CoNi)-MOF is basically the same as the preparation method in Example 1, except that the Fe(NO3)3·9H2O in step 1 is changed from 1.67mmol to 3mmol, the Co(NO3)2·6H2O is changed from 1.67mmol to 1mmol, and the Ni(NO3)2·6H2O is changed from 1.67mmol to 1mmol, to prepare Fe3(CoNi)-MOF.

[0046] Embodiment 4

[0047] Fe x Preparation of (CoNi)-MOF@NF

[0048] (1) Weigh 2 mg of FeCoNi-MOF, Fe2(CoNi)-MOF and Fe3(CoNi)-MOF and mix the three different Fe x (CoNi)-MOF was dissolved in a mixed solution consisting of 20 μL 5wt.% naphthol, 200 μL anhydrous ethanol and 100 μL deionized water. The mixture was ultrasonicated for 60 min to obtain uniformly dispersed sample solutions B1, B2 and B3. Solution B1 was a FeCoNi-MOF solution, solution B2 was a Fe2(CoNi)-MOF solution, and solution B3 was a Fe3(CoNi)-MOF solution.

[0049] (2) A nickel foam with a size of 1 cm*2 cm was ultrasonically cleaned with 1 mmol / L HCL, 1 mmol / L NaOH, acetone, deionized water, and anhydrous ethanol for 1 h each, and then dried in a vacuum oven for 2 h at a temperature of 50°C.

[0050] (3) The solution B1, solution B2, and solution B3 obtained above were respectively dripped onto the 1 cm*1 cm position of the nickel foam obtained in step (2) using a pipette at a frequency of 20 μL / time, with the time interval between each dripping being 5 min. This operation was repeated until all the solutions were dripped. The samples were dried in an oven for 1 h at a temperature of 40 °C to obtain FeCoNi-MOF@NF, Fe2(CoNi)-MOF@NF, and Fe3(CoNi)-MOF@NF.

[0051] Embodiment 5

[0052] The FeCoNi-MOF, Fe2(CoNi)-MOF and Fe3(CoNi)-MOF prepared in Examples 1 to 3 were subjected to X-ray diffraction and transmission electron microscopy (TEM) tests.

[0053] Please refer to Figure 1-Figure 2 The FeCoNi-MOF, Fe2(CoNi)-MOF and Fe3(CoNi)-MOF prepared in Examples 1 to 3 were subjected to X-ray diffraction to obtain Fe x XRD patterns of (CoNi)-MOF materials, Fe x (CoNi)-MOF shows typical diffraction peaks, which can be indexed to the standard MIL-53 (CCDC No. 2088536) spectrum. The diffraction peak at 9.8° is consistent with the (200) crystal plane of standard MIL-53. x The morphology of (CoNi)-MOF materials is as follows Figure 2 As shown, from left to right are FeCoNi-MOF, Fe2(CoNi)-MOF and Fe3(CoNi)-MOF. It can be seen from the TEM image that Fe x (CoNi)-MOF exhibits a spindle-shaped morphology with an average diameter of about 250 nm. x (CoNi)-MOF was successfully prepared.

[0054] Embodiment 6

[0055] Electrochemical tests were performed on the FeCoNi-MOF@NF, Fe2(CoNi)-MOF@NF and Fe3(CoNi)-MOF@NF prepared in Example 4.

[0056] The electrochemical tests were carried out in a standard three-electrode system of an electrochemical workstation (CHI 760E) at 25 °C.

[0057] The FeCoNi-MOF@NF, Fe2(CoNi)-MOF@NF and Fe3(CoNi)-MOF@NF obtained in Example 4 were used as working electrodes, saturated Ag / AgCl (1MKOH) was used as reference electrode, and carbon rod (HER) / platinum sheet (OER) was used as counter electrode. All points were referred to the reversible hydrogen electrode (RHE) formula:

[0058] E(REH)=E(Ag / AgCl)+0.059×pH+0.197V

[0059] The electrochemical properties were determined by linear sweep voltammetry (LSV) at room temperature in 1 M KOH solution at a scan rate of 5 mV / s, and electrochemical impedance spectroscopy (EIS) was performed in the range of 10-2 to 104 Hz.

[0060] Please refer to Figure 3-Figure 6 Fe2(CoNi)-MOF@NF has a lower overpotential than other MOFs, and the reaction kinetics are significantly enhanced. Fe2(CoNi)-MOF@NF has a smaller impedance and the largest electrochemically active surface area.

[0061] Please refer to Figure 7-10 Fe2(CoNi)-MOF@NF has a lower overpotential than other MOFs, and the reaction kinetics are significantly enhanced. Fe2(CoNi)-MOF@NF has a smaller impedance and the largest electrochemically active surface area.

[0062] Combined with the electrochemical performance test results, it can be seen that Fe2(CoNi)-MOF@NF has excellent HER and OER catalytic performance.

[0063] The technical solutions in the above embodiments of the present application have at least the following technical effects:

[0064] Fe2(CoNi)-MOF has excellent HER and OER catalytic activity and can replace precious metal catalysts for wide application.

[0065] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0066] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. The preparation method of multi-metal MOF bifunctional catalyst, the specific steps are as follows: Step 1: dissolve two or more different metal salts and an organic dibasic acid in N,N-dimethylformamide in a certain proportion, and stir evenly to obtain solution A; Step 2: Transfer the solution A obtained in step 1 to a reactor, dry, centrifuge, wash, and then dry to obtain a multi-metal MOF material.

2. The method according to claim 1, characterized in that There are three kinds of metal salts in step 1, specifically iron nitrate nonahydrate, cobalt nitrate hexahydrate and nickel nitrate hexahydrate.

3. The method according to claim 2, characterized in that The organic dibasic acid is fumaric acid.

4. The method according to claim 3, characterized in that The reaction temperature of the reactor is 100-120° C., and the reaction time is 8-10 hours.

5. The method according to claim 2, characterized in that The molar mass ratio of the ferric nitrate nonahydrate, the cobalt nitrate hexahydrate and the nickel nitrate hexahydrate is 1-3:1:

1.

6. The method according to claim 3, characterized in that The molar mass ratio of the ferric nitrate nonahydrate, the cobalt nitrate hexahydrate, the nickel nitrate hexahydrate and the fumaric acid is 1-3:1:1:24-40.

7. The method according to claim 6, characterized in that The molar mass ratio of the ferric nitrate nonahydrate, the cobalt nitrate hexahydrate, the nickel nitrate hexahydrate and the trans-butadienoic acid is 2:1:1:

32.

8. Multi-metal MOF bifunctional catalyst, characterized in that: Prepared by the preparation method according to any one of claims 1 to 6.

9. Use of the multi-metal MOF bifunctional catalyst as claimed in claim 8 in water electrolysis reaction.

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