Preparation method of nickel-containing metal organic framework material and application of nickel-containing metal organic framework material to oxygen evolution material in electrocatalytic water decomposition process

Abstract

The invention discloses a preparation method of a nickel-containing metal organic framework material and application of the nickel-containing metal organic framework material to an oxygen evolution material in the electrocatalytic water decomposition process. The novel chromium-nickel dissimilar metal organic framework material is obtained by self-assembling in a mixed solution of 1, 2-diketone, nickel nitrate hexahydrate, chromium nitrate nonahydrate, sodium hydroxide and deionized water, and the synthetic material is assembled into a three-electrode system which is used as a catalyst material for oxygen evolution reaction to test the electro-catalytic performance. The metal organic framework material has the advantages that the ligand used by the metal organic framework material is relatively low in cost, simple in synthesis process and high in purity; and the oxygen affinity of Cr and Ni are utilized to generate a synergistic effect, so that active sites are increased, and the electro-catalytic performance of the material is optimized and improved. According to experimental test data analysis, the Cr0. 17Ni-MOF material has excellent electro-catalytic oxygen evolution performance, the overpotential at 10 mA. Cm <-2 > is only 175 mv, and the Cr0. 17Ni-MOF material is superior to metal organic framework materials doped with chromium in other proportions.

Description

Technical Field

[0001] The present invention relates to a metal organic framework material (Ni-MOF) formed with an organic ligand 3,4-dihydroxy-3-cyclobutene-1,2-dione and transition metal nickel as metal centers. Under the condition that the structure of the Ni-MOF is not changed, chromium salts are doped and combined to obtain a novel chromium-nickel heterometallic organic framework material. The material is tested by preparing catalyst electrode materials and shows excellent performance in oxygen evolution reaction. Background Art

[0002] The oxygen evolution reaction (OER) is an important half-reaction in many new energy conversion technologies (such as water electrolysis, CO2 reduction, metal-air batteries, etc.). However, due to the sluggish kinetics of the oxygen evolution reaction, low reaction activity, and the need for a higher actual electrolysis voltage, the improvement of the OER catalytic performance is limited. Therefore, it is urgent to reduce the energy barrier of the oxygen evolution reaction and improve the energy conversion efficiency. The traditional excellent OER catalysts are mainly precious metal-based materials (RuO2, IrO2, etc.), but the high cost and poor stability of precious metals have seriously limited the practical application of precious metal-based OER catalysts. Therefore, it is very important to explore an efficient, cheap, and abundant oxygen evolution catalyst.

[0003] Metal-organic framework materials (MOFs) are a type of crystalline porous materials with a periodic network structure formed by the self-assembly of inorganic metal centers (metal ions or metal clusters) and organic ligands. They have attracted widespread attention from researchers due to their controllable three-dimensional structure, the potential to change metal cations, and feasible post-synthesis modification. Transition metal elements such as Ni and Co have theoretical electrocatalytic properties close to those of precious metal catalysts, and have multi-valent active centers. They are relatively abundant in the earth's crust, inexpensive, and easy to self-assemble with organic ligands to form metal-organic frameworks. At the same time, Cr, an oxygen-philic element, has a synergistic effect with Ni, which can change the position of the d-band center and improve the activity of the material in oxygen evolution reaction, and has important development and application prospects. Summary of the invention

[0004] The purpose of the present invention is to synthesize a novel chromium-nickel heterometallic organic framework material preparation method and its application by doping the oxygen-philic metal Cr with a nickel metal organic framework, utilizing the synergistic effect of the two to change the d-band center, and adjusting the molar ratio of the two, specifically a CrNi-MOF material, and exploring the oxygen evolution properties, while analyzing its oxygen evolution (OER) performance.

[0005] Based on the above objectives, the present invention provides a metal organic framework material (Ni-MOF) formed by using 3,4-dihydroxy-3-cyclobutene-1,2-dione (SA) as a ligand and transition metal nickel as a metal center, and also contains chromium to obtain a chromium-nickel heterometallic organic framework material. The specific method is as follows: Take 3,4-dihydroxy-3-cyclobutene-1,2-dione (SA), nickel nitrate hexahydrate, sodium hydroxide (adjust pH to 4.5-5.5), deionized water, mix them, disperse them evenly by ultrasonication, seal them, and react them under solvent thermal conditions of 100-120 °C, reaction time of 2-15 h, and cool them to room temperature at a constant rate of 2-3 °C / h to obtain green block crystals. The dried material is used to prepare electrode materials for testing oxygen evolution reaction.

[0006] The molar ratio of 3,4-dihydroxy-3-cyclobutene-1,2-dione (SA) and nickel nitrate hexahydrate described in the step is preferably 3:4, sodium hydroxide is added to adjust the pH to 4.5-5.5, the reaction conditions are 120°C, the preferred reaction time is 2 h, and the pH is 5.

[0007] The same steps and methods are used, except that chromium nitrate nonahydrate and nickel nitrate hexahydrate are simultaneously put into a glass bottle at a molar ratio of 6:1-10:1 (some preferred schemes are 6:1, 8:1, 10:1), ultrasonically dispersed in an ultrasonicator, and then thermally reacted under the same conditions as above.

[0008] The sample obtained in the above steps is centrifuged to collect the precipitate, which is centrifugally washed multiple times with deionized water and ethanol respectively, and the obtained product is dried in a vacuum drying oven at 60-80°C and ground, and the sample is collected to obtain a Cr-containing nickel metal organic framework crystalline material.

[0009] The centrifugal rate is 5000-9000 rpm / min, the centrifugal time is 3-5 min, and the obtained product is dried under vacuum at a temperature of 60°C, a pressure of 10 MPa, and a drying time of 12-16 h.

[0010] Another technical solution of the present invention is to use the CrNi-MOF or Ni-MOF obtained in the above steps as a catalyst electrode material to test that it has excellent performance in oxygen evolution reaction (OER). The room temperature involved in the present invention refers to the ambient temperature under normal pressure.

[0011] The beneficial effects of the present invention are as follows: (1) The material synthesis method is simple, the raw material price is low, the cost is low, it is easy to obtain, easy to separate and wash, easy to operate, and has low equipment requirements.

[0012] (2) The doping of the oxygen-philic element Cr effectively changes the Fermi level of the transition metal Ni, reduces the reaction energy barrier, and is more conducive to the oxygen evolution reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 : This is a physical picture of the Ni-MOF synthesized in Example 1.

[0014] Figure 2 : Cr doped with Cr metal synthesized in Example 3 0.17 Physical picture of Ni-MOF.

[0015] Figure 3 : Thermogravimetric diagram of the Ni-MOF synthesized in Example 1.

[0016] Figure 4 : Cr synthesized in Example 3 0.17 Thermogravimetric diagram of Ni-MOF.

[0017] Figure 5 : Ni-MOF synthesized in Example 1, Example 2, and Example 3 and Cr doped in different proportions 0.1 Ni-MOF、Cr 0.13 Ni-MOF、Cr 0.17 XRD spectra of Ni-MOF compared with simulated peaks.

[0018] Figure 6 : Ni-MOF synthesized in Example 1, Example 2, and Example 3 and Cr doped in different proportions 0.1 Ni-MOF、Cr 0.13 Ni-MOF、Cr 0.17 Fourier transform infrared spectrum of Ni-MOF.

[0019] Figure 7 :SEM image of the Ni-MOF sample synthesized in Example 1.

[0020] Figure 8 : Cr obtained in Example 3 0.17 Scanning electron microscopy image of Ni-MOF sample.

[0021] Fig. 9 : Ni-MOF prepared in Example 1, Example 2, and Example 3 and Cr doped in different proportions 0.1 Ni-MOF、Cr 0.13 Ni-MOF、Cr 0.17 Comparison of oxygen evolution polarization curves of Ni-MOF materials.

[0022] Fig.10 : Ni-MOF prepared in Example 1, Example 2, and Example 3 and Cr doped in different proportions 0.1 Ni-MOF、Cr 0.13 Ni-MOF、Cr 0.17 Oxygen evolution Tafel curve of Ni-MOF material.

[0023] Fig.11 : Ni-MOF prepared in Example 1, Example 2, and Example 3 and Cr doped in different proportions0.1 Ni-MOF、Cr 0.13 Ni-MOF、Cr 0.17 Ni-MOF material 10 mA·cm -2 , 50 mA·cm -2 The corresponding overpotential histogram. DETAILED DESCRIPTION

[0024] Example 1 Prepare 1 mmol·L -1 1 mmol·L sodium hydroxide solution; weigh 0.3 mmol 3,4-dihydroxy-3-cyclobutene-1,2-dione (SA), 0.4 mmol nickel nitrate hexahydrate, and 10 ml deionized water in equal amounts, add them into 20 ml glass vials, and then add 1 mmol·L -1 The sodium hydroxide solution was added to adjust the pH value of the solution to 3, 5, 7, and 9, and each vial was ultrasonicated for 30 min and placed in a 120 ℃ oven for constant temperature reaction for 2 h, and then cooled to room temperature at a constant rate of 3 ℃ / h. The color of the solution before the reaction was a light green clear liquid. After the thermal reaction, light green crystals were generated in the vial with a pH of 5 after the addition of sodium hydroxide (such as Figure 1 , 7 The sample was centrifuged at 9000 rpm / min for 3 min. The sample was vacuum dried at 60 °C and 10 MPa for 12-16 h. The sample was ground and placed in a sample tube, which was recorded as a Ni-MOF sample.

[0025] Example 2 Weigh 0.3 mmol 3,4-dihydroxy-3-cyclobutene-1,2-dione (SA), 0.4 mmol nickel nitrate hexahydrate, and 0.04 mmol chromium nitrate nonahydrate in equal amounts into each vial, add 10 ml of deionized water, and add the prepared 1 mmol·L -1 Sodium hydroxide solution was added to adjust the solution pH to 5. Each vial was ultrasonicated for 30 min and placed in a 120 ℃ oven for constant temperature reaction for 5 h, 10 h, and 15 h, and then cooled to room temperature at a constant rate of 3 ℃ / h. The solution was blue before the reaction, and blue-green crystals were produced in the vial after 15 h of reaction. Then centrifugation was performed at a centrifugal rate of 9000 rpm / min and a centrifugal time of 3 min. The sample obtained by centrifugation was vacuum dried at a temperature of 60 ℃ and a pressure of 10 MPa for 12-16 h. Finally, the sample obtained by vacuum drying was ground and placed in a sample tube, recorded as Cr 0.1 Ni-MOF samples.

[0026] Example 3 Weigh 0.3 mmol 3,4-dihydroxy-3-cyclobutene-1,2-dione (SA), 0.4 mmol nickel nitrate hexahydrate, and 0.05 mmol and 0.07 mmol chromium nitrate nonahydrate, respectively, in equal amounts, add 10 ml of deionized water to each vial, and add the prepared 1 mmol·L -1 Sodium hydroxide solution was added to adjust the solution pH to 5. Each reaction was ultrasonicated for 30 min and placed in a 120°C oven for constant temperature reaction for 15 h, and then cooled to room temperature at a constant rate of 2-3°C / h. The solution was blue before the reaction, and blue-green crystals were produced in the vial after the reaction. Then centrifugation was performed at a centrifugal rate of 9000 rpm / min for 3 min. The sample obtained by centrifugation was vacuum dried at a temperature of 60°C and a pressure of 10 MPa for 12-16 h. Finally, the sample obtained by vacuum drying was ground and placed in a sample tube, recorded as Cr 0.13 Ni-MOF, Cr 0.17 Ni-MOF samples (such as Figure 2 , 8 as shown).

[0027] Example 4 4 mg of the samples obtained in the above-mentioned Examples 1, 2 and 3 were weighed, respectively, and added with 1.2 ml of anhydrous ethanol, 0.6 ml of deionized water and 0.2 ml of 0.5% naphthol. After ultrasonication for 30 min, 120 μL of the dispersion was taken with a pipette and applied on a carbon cloth as a working electrode, a platinum wire was used as a counter electrode, and a mercury-mercury oxide electrode was used as a reference electrode. The oxygen evolution (OER) performance of the material was tested in a 1M KOH solution. After CV scanning to stability, LSV scanning test was performed as follows: Fig.11 It is found that at a current density of 10 mA·cm -2 When the overpotential Cr 0.17 Ni-MOF (175 mV)>Cr 0.13 Ni-MOF (253 mV)>Ni-MOF (255 mV)>Cr 0.1 Ni-MOF (368 mV) at a current density of 50 mA cm -2 When the overpotential is 319 mV, 423 mV, 472 mV, and 492 mV, respectively, Cr 0.17 The Tafel slope of Ni-MOF is also the smallest, which is 90.86 mV·dec. -1 .

[0028] The oxygen evolution performance of the composite materials CrNi-MOF with different proportions synthesized by the above method was tested, and it was found that the chromium-doped composite material Cr 0.17 Ni-MOF, Cr 0.13 Ni-MOF has good oxygen evolution performance at a current density of 10 mA·cm -2 When the overpotential is 175 mV and 253 mV respectively, Cr 0.17 The oxygen evolution performance of Ni-MOF reached a maximum of 175 mV.

Claims

1. A method for preparing a nickel-containing metal organic framework material, characterized in that: The steps are as follows: deionized water is added to 3,4-dihydroxy-3-cyclobutene-1,2-dione and nickel nitrate hexahydrate, and a sodium hydroxide solution is added to obtain a nickel-based metal organic framework material Ni-MOF composite material through a hydrothermal reaction.

2. The method for preparing a nickel-containing metal organic framework material according to claim 1, characterized in that: The molar ratio of 3,4-dihydroxy-3-cyclobutene-1,2-dione to nickel nitrate hexahydrate is 3:4-3:

8.

3. The method for preparing a nickel-containing metal organic framework material according to claim 2, characterized in that: The nickel salt also contains chromium salt, so a nickel-chromium-based metal organic framework material CrNi-MOF composite material is prepared; The nickel salt includes nickel nitrate hexahydrate; the chromium salt includes chromium nitrate nonahydrate.

4. The method for preparing a nickel-containing metal organic framework material according to claim 3, characterized in that: The molar ratio of the 3,4-dihydroxy-3-cyclobutene-1,2-dione, nickel nitrate hexahydrate and chromium nitrate nonahydrate is 3:4:0.4-3:4:0.

7.

5. The method for preparing a nickel-containing metal organic framework material according to claim 1, characterized in that: The solvent thermal reaction conditions are 100~120 ℃ and the reaction time is 2-15 hours.

6. The method for preparing a nickel-containing metal organic framework material according to claim 5, characterized in that: The solvothermal reaction conditions were 120 °C and the reaction time was 15 h.

7. Use of the Ni-MOF or CrNi-MOF composite material prepared according to the method according to any one of claims 1 to 6 as an oxygen evolution material.

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