Preparation method of nickel-containing metal organic framework material and application of the same on oxygen evolution material in electrocatalytic water splitting process

Abstract

The application discloses a preparation method of a nickel-containing metal organic framework material and application of the material to an oxygen evolution material in an electrocatalytic water decomposition process, and particularly relates to a novel chromium-nickel heterometallic organic framework material obtained by self-assembly in a mixed solution of an organic ligand 3,4-dihydroxy-3-cyclobutene-1,2-diketone, nickel nitrate hexahydrate, chromium nitrate nonahydrate, sodium hydroxide and deionized water. The synthesized material is assembled into a three-electrode system and is used as a catalyst material for an oxygen evolution reaction to test the electrocatalytic performance. The metal organic framework material has the advantages that the ligand used in the material has low cost, simple synthesis process and high purity; the oxygen affinity of Cr and the synergistic effect of Ni are utilized to increase active sites and optimize and improve the electrocatalytic performance of the material. Through analysis of the experimental test data, it is found that the Cr 0.17 The Ni-MOF material has superior electrocatalytic oxygen evolution performance, and the overpotential is only 175 mv at 10 mA·cm ‑2 , which is superior to other proportions of chromium-doped metal organic framework materials.

Description

TECHNICAL FIELD

[0001] The application relates to a metal organic framework material (Ni-MOF) formed by taking an organic ligand 3,4-dihydroxy-3-cyclobutene-1,2-dione and a transition metal nickel as a metal center, a new chromium-nickel heterometallic organic framework material obtained by doping a chromium salt in the structure of the Ni-MOF without changing the structure, and the material shows excellent performance on an oxygen evolution reaction by testing a prepared catalyst electrode material. BACKGROUND

[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 slow kinetics of the oxygen evolution reaction, the low reaction activity, and the high actual electrolysis voltage required, 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. Traditional excellent OER catalysts are mainly noble metal-based materials (RuO2, IrO2, etc.), but the high cost and poor stability of noble metals seriously limit the practical application of noble metal-based OER catalysts. Therefore, it is crucial to explore an efficient, inexpensive and abundant oxygen evolution catalyst.

[0003] Metal organic framework materials (MOFs) are a kind of crystalline porous materials with periodic network structure formed by self-assembly of inorganic metal centers (metal ions or metal clusters) and organic ligands. Due to the advantages of controllable three-dimensional structure, potential change of metal cations and feasible post-synthesis modification, the metal organic framework materials have attracted extensive attention of researchers. Transition metal elements such as Ni and Co have theoretical electrocatalytic performance close to that of noble metal catalysts, and have variable valence active centers, are relatively abundant in the earth's crust, are low in price, and are easy to self-assemble into metal organic frameworks with organic ligands. At the same time, the oxygenophilic element Cr and Ni produce a synergistic effect, which can change the position of the d-band center and improve the activity of the material in the oxygen evolution reaction, and has important development and application prospects. SUMMARY

[0004] The application aims to synthesize a new chromium-nickel heterometallic organic framework material by doping the oxygenophilic metal Cr into the nickel metal organic framework, changing the d-band center by using the synergistic effect of the two, adjusting the molar ratio of the two, and exploring the oxygen evolution properties of the CrNi-MOF material, and analyzing the oxygen evolution (OER) performance.

[0005] Based on the above purpose, the application provides a metal organic framework material (Ni-MOF) formed by taking 3,4-dihydroxy-3-cyclobutene-1,2-dione (SA) as a ligand and a transition metal nickel as a metal center, and a chromium-nickel heterometallic organic framework material containing chromium. The specific method is as follows:

[0006] Take 3,4-dihydroxy-3-cyclobutene-1,2-dione (SA), nickel nitrate hexahydrate, sodium hydroxide (adjust pH to 4.5-5.5), deionized water, ultrasonic dispersion after mixing, seal, under solvothermal reaction conditions of 100-120 ℃, reaction time is 2-15 h, and uniform speed of 2-3 ℃ / h to room temperature, get green block crystal. Dry to obtain material preparation electrode material test oxygen evolution reaction.

[0007] The molar ratio of 3,4-dihydroxy-3-cyclobutene-1,2-dione (SA) and nickel nitrate hexahydrate in the step is preferably 3:4, sodium hydroxide is added to adjust the pH to 4.5-5.5, the reaction condition is 120 ℃, and the preferred reaction time is 2 h and the pH is 5.

[0008] The same step method, except that the chromium nitrate nonahydrate and the nickel nitrate hexahydrate are placed in a glass bottle at a molar ratio of 6:1-10:1 (some preferred ratios are 6:1, 8:1, and 10:1), and ultrasonic dispersion is performed in an ultrasonic instrument, and then the same conditions as above are used for thermal reaction.

[0009] The sample obtained by the above steps is centrifuged to collect the precipitate, washed with deionized water and ethanol, dried in a vacuum drying oven at 60-80 ℃, and ground, and the sample is collected to obtain a Cr-containing nickel metal organic framework crystalline material.

[0010] The centrifugal speed is 5000-9000 rpm / min, the centrifugal time is 3-5 min, the vacuum drying temperature is 60 ℃, the pressure is 10 MPa, and the drying time is 12-16 h.

[0011] Another technical solution of the present application is that the CrNi-MOF or Ni-MOF obtained by the above steps is used as a catalyst electrode material to test the excellent performance of the oxygen evolution reaction (OER).

[0012] The present application has the following advantages:

[0013] (1) The material synthesis method is simple, the raw material price is low, the cost is small, it is easy to obtain, easy to separate and wash clean, easy to operate, and the equipment requirement is low.

[0014] (2) The doping of oxygen element Cr effectively changes the Fermi level of transition metal Ni, reduces the reaction energy barrier, and is more conducive to the progress of the oxygen evolution reaction. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1: Ni-MOF synthesized for example 1.

[0016] Figure 2 : Cr doped Ni-MOF synthesized for example 3. 0.17 Ni-MOF synthesized for example 1.

[0017] Figure 3 : Thermogravimetric plot of Ni-MOF synthesized for example 1.

[0018] Figure 4 : Cr doped Ni-MOF synthesized for example 3. 0.17 Thermogravimetric plot of Ni-MOF synthesized for example 1.

[0019] Figure 5 : Ni-MOF synthesized for example 1, 2, 3 and Cr doped at different ratios. 0.1 Ni-MOF, Cr 0.13 Ni-MOF, Cr 0.17 XRD pattern of Ni-MOF compared to simulated peaks.

[0020] Figure 6 : Ni-MOF synthesized for example 1, 2, 3 and Cr doped at different ratios. 0.1 Ni-MOF, Cr 0.13 Ni-MOF, Cr 0.17 Fourier transform infrared spectroscopy of Ni-MOF.

[0021] Figure 7 : Scanning electron microscopy of Ni-MOF sample synthesized for example 1.

[0022] Figure 8 : Cr doped Ni-MOF prepared for example 3. 0.17 Scanning electron microscopy of Ni-MOF sample synthesized for example 1.

[0023] Figure 9 : Ni-MOF prepared for example 1, 2, 3 and Cr doped at different ratios. 0.1 Ni-MOF, Cr 0.13 Ni-MOF, Cr 0.17 Comparison of oxygen evolution polarization curves of Ni-MOF materials.

[0024] Figure 10 : Ni-MOF prepared for example 1, 2, 3 and Cr doped at different ratios. 0.1 Ni-MOF, Cr 0.13 Ni-MOF, Cr 0.17 Oxygen evolution Tafel curves of Ni-MOF materials.

[0025] Figure 11Ni-MOF prepared for Example 1, Example 2, Example 3 and Cr doped in different proportions 0.1 Ni-MOF, Cr 0.13 Ni-MOF, Cr 0.17 Ni-MOF material 10 mA·cm -2 , 50 mA·cm -2 Corresponding overpotential column chart. DETAILED DESCRIPTION

[0026] Example 1

[0027] A 1 mmol·L -1 solution of sodium hydroxide was prepared; an equal amount of 0.3 mmol 3,4-dihydroxy-3-cyclobutene-1,2-dione (SA), 0.4 mmol of nickel nitrate hexahydrate, 10 ml of deionized water were weighed into each 20 ml glass vial, and a prepared 1 mmol·L -1 solution of sodium hydroxide was added to each vial, and the pH of the solution was adjusted to 3, 5, 7, and 9, respectively. 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 uniform rate of 3 ℃ / h. The color of the solution before reaction was light green clear liquid, and after heat reaction, light green crystals were generated in the vial with pH 5 of sodium hydroxide (as shown in Figure 1 , 7 After centrifugation at a speed of 9000 rpm / min for 3 min, the samples were vacuum dried at a temperature of 60 ℃, a pressure of 10 MPa, and a time of 12-16 h. Finally, the vacuum-dried samples were ground and loaded into sample tubes, labeled as Ni-MOF samples.

[0028] Example 2

[0029] An equal amount of 0.3 mmol 3,4-dihydroxy-3-cyclobutene-1,2-dione (SA), 0.4 mmol of nickel nitrate hexahydrate, and 0.04 mmol of chromium nitrate nonahydrate were weighed into each 20 ml glass vial, and 10 ml of deionized water was added to each vial, and a prepared 1 mmol·L -1adjusted to pH 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 uniform 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 speed of 9000 rpm / min for 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 vacuum-dried sample was ground and loaded into a sample tube, and was recorded as Cr 0.1 Ni-MOF sample.

[0030] Example 3

[0031] An equal amount of 0.3 mmol of 3,4-dihydroxy-3-cyclobutene-1,2-dione (SA), 0.4 mmol of nickel nitrate hexahydrate, 0.05 mmol and 0.07 mmol of chromium nitrate nonahydrate were weighed, respectively, 10 ml of deionized water was added to each vial, and 1 mmol·L -1 of sodium hydroxide solution was added, the solution pH was adjusted to 5, each reaction was ultrasonicated for 30 min and placed in a 120 ℃ oven for constant temperature reaction for 15 h, and then cooled to room temperature at a uniform rate of 2-3 ℃ / 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 speed of 9000 rpm / min for 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 vacuum-dried sample was ground and loaded into a sample tube, and was recorded as Cr 0.13 Ni-MOF, Cr 0.17 Ni-MOF sample (as shown in Figure 2 , 8 ).

[0032] Example 4

[0033] The samples obtained in the above examples 1, 2 and 3 were weighed at 4 mg each, added to 1.2 ml of anhydrous ethanol, 0.6 ml of deionized water and 0.2 ml of 0.5% naphthol, and ultrasonicated for 30 min. 120 μL of the dispersion was taken by a pipette and coated on a carbon cloth to serve 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 material was tested for oxygen evolution (OER) performance in a 1M KOH solution. After CV scanning to stability, LSV scanning test was performed as Figure 11 . It was found that the overpotential of the material was Cr -2 when the current density was 10 mA·cm 0.17Ni-MOF (175 mV)>Cr 0.13 Ni-MOF (253 mV)>Ni-MOF (255 mV)>Cr 0.1 Ni-MOF (368 mV), the overpotential is 319 mV, 423 mV, 472 mV and 492 mV respectively when the current density is 50 mA·cm -2 0.17 The Tafel slope of Ni-MOF is also the smallest, which is 90.86 mV·dec -1 .

[0034] The different proportions of composite materials CrNi-MOF synthesized by the above method were tested for oxygen evolution performance, and it was found that the oxygen evolution performance of Ni-MOF and its chromium-doped composite material Cr 0.17 Ni-MOF, Cr 0.13 Ni-MOF is good, and the overpotential is 175 mV, 253 mV respectively when the current density is 10 mA·cm -2 0.17 The oxygen evolution performance of Ni-MOF is the highest, which is 175 mV.​​

Claims

1. A method for preparing a nickel-containing metal-organic framework material, characterized in that, The steps are as follows: 3,4-dihydroxy-3-cyclobutene-1,2-dione, nickel nitrate hexahydrate, chromium nitrate nonahydrate are added into deionized water, and a sodium hydroxide solution is added to obtain a nickel-chromium-based metal organic framework material CrNi-MOF composite material through a hydrothermal reaction; the molar ratio of 3,4-dihydroxy-3-cyclobutene-1,2-dione, nickel nitrate hexahydrate and chromium nitrate nonahydrate is 3:4:0.4-3:4:0.

7.

2. The method for preparing the nickel-containing metal-organic framework material according to claim 1, characterized in that, The solvothermal reaction condition is 100-120 DEG C, and the reaction time is 2-15 hours.

3. The method for preparing the nickel-containing metal-organic framework material according to claim 2, characterized in that, The solvothermal reaction condition is 120 DEG C, and the reaction time is 15 hours.

Images