CN110655654A - Preparation and oxygen evolution properties of a two-dimensional layered cobalt-based metal-organic framework (Co-MOF) electrode material - Google Patents

Abstract

The invention belongs to the technical field of novel energy, and particularly relates to preparation of a two-dimensional layered Co-MOF electrode material with remarkably improved water oxidation performance and oxygen evolution performance research. The invention prepares a two-dimensional layered Co-MOF electrode material by a simple and mild hydrothermal method, and then uses the prepared electrode material for the oxidation performance research of electrolyzed water, comprising the following steps: preparing a two-dimensional layered Co-MOF electrode material by a hydrothermal method; and (3) researching the oxygen evolution performance of the prepared electrode material. The invention has the beneficial effects that: the two-dimensional layered Co-MOF electrode material has good stability, good oxygen evolution reaction performance and wide application prospect in the technical field of novel energy.

Description

Preparation and preparation of a two-dimensional layered cobalt-based metal-organic framework (Co-MOF) electrode material Oxygen evolution performance research

technical field

The invention belongs to the technical field of novel energy, and in particular relates to the preparation of a two-dimensional layered Co-MOF electrode material with significantly improved water oxidation performance and research on the oxygen evolution performance.

Background technique

With the development of science and technology, people's increasing demand for energy has forced people to find a new generation of clean, efficient and renewable energy conversion and storage systems. Recently, scientists have made new research progress on water that can be seen everywhere in our daily life. At present, a variety of efficient and fast hydrogen production methods have been explored, such as photolysis of water, electrolysis of power generation and water supply, nuclear energy cracking, steam reforming, etc. The process at the heart of these studies is the oxygen evolution reaction (OER), which often occurs at the interface between phases (solids, liquids, gases). Therefore, in order to promote the oxygen evolution reaction to improve the activity of the oxygen evolution reaction and improve the energy efficiency, it is imperative to develop an electrode material with high catalytic water electrolysis performance.

At present, the preparation of electrode materials with porous metal-organic frameworks (MOFs) as complexes has become a hot research topic. This material has a large specific surface area, a uniform structure, and a tunable composition. This is due to its variable metal center and organic ligands. lead to. For the selection of the metal center of the MOF material, almost all metals in the periodic table can be covered, but Co, Cu, etc. are more widely used. Metal ions play the role of catalytic active centers in the entire metal-organic framework precursor material, while most organic ligands play the role of microporous framework in the entire MOF material. Metal ions of organic ligands have many active centers, which can facilitate multi-channel propagation and diffusion during reactions and interactions. At the same time, the MOF framework possesses a complex active site structure, which will provide a suitable site for the synthesis of electrocatalyst materials with excellent performance.

SUMMARY OF THE INVENTION

Based on the above reasons, the present invention provides a simple and mild preparation method of two-dimensional layered Co-MOF electrical material, and then the prepared electrode material is used to study the oxidation performance of electrolyzed water. The specific steps for preparing the two-dimensional layered Co-MOF electrode material involved in the present invention are as follows:

(1) Accurately measure 128mL DMF (N,N-dimethylformamide), 8mL ethanol, and 8mL deionized water in a 250mL beaker, and seal with disposable plastic film and rubber band to prevent DMF and ethanol from volatilizing. After mixing uniformly, weigh 0.4984 g (3 mmol) of terephthalic acid (H2BDC), then place it under ultrasonic conditions (40KHz) and add 0.7472 g (3 mmol) of cobalt acetate tetrahydrate (C4H6CoO4•4H2O), transfer to hydrothermal in the kettle;

(2) The hydrothermal kettle is placed in an oven for the reaction, the hydrothermal kettle after the reaction is completed and cooled to room temperature is taken out, the metal organic framework generated therein is poured out, cooled and centrifuged for 2 to 3 times, and then distilled water is used. Hang the remaining solid in the centrifuge tube into a watch glass with a glass rod and dry it in a constant temperature oven at 60°C to remove moisture. After the product was completely dried, the petri dish was taken out, ground evenly, and marked as Co-MOF.

Further, in step (1), the volume ratio of DMF, ethanol and deionized water is 16:1:1; the molar ratio of organic ligand terephthalic acid and cobalt acetate tetrahydrate is 1:1.

Further, the hydrothermal reaction temperature of the solution in step (2) is 140° C.; the reaction time is 12, 24, and 48 hours.

Further, in step (2), the time for the hydrothermal reactor to be cooled to room temperature is 8 to 10 hours.

Further, in step (2), the drying time in the 60°C constant temperature oven is 4-6 hours.

The beneficial effects of the present invention are:

The two-dimensional layered Co-MOF electrode material prepared by the invention has good stability and good oxygen evolution reaction performance, and has broad application prospects in the field of new energy technology.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings.

1 is the XRD pattern of the two-dimensional layered Co-MOF electrode material in Example 1

2 is a SEM image of the two-dimensional layered Co-MOF electrode material prepared in Example 1

3 is a comparison of the oxygen evolution performance of the two-dimensional layered Co-MOF electrode material and Cu-MOF in Comparative Example 2.

Detailed ways

The present invention will now be further described with reference to specific embodiments, and the following embodiments are intended to illustrate the present invention rather than further limit the present invention.

Example 1:

The preparation of composite electrode material includes the following steps:

(1) Accurately measure 128mL DMF (N,N-dimethylformamide), 8mL ethanol, and 8mL deionized water in a 250mL beaker, and seal with disposable plastic film and rubber band to prevent DMF and ethanol from volatilizing. After mixing evenly, weigh 0.4984g (3mmol) of terephthalic acid (H2BDC), then place it under ultrasonic conditions (40 KHz) and add 0.7472g (3mmol) of cobalt acetate tetrahydrate (C4H6CoO4•4H2O), transfer to water in the hot kettle;

(2) React the hydrothermal kettle in an oven at 140°C for 24 hours, take out the cooled hydrothermal kettle after the reaction is completed, pour out the metal organic framework formed therein, cool it to room temperature and perform centrifugation for 2 to 3 times, Then use distilled water and a glass rod to scrape the remaining solid in the centrifuge tube into a watch glass and put it into a 60 ℃ constant temperature oven to dry to remove the water therein. After the product is completely dried, it is ground evenly, and it is packaged for later use. Figure 1 is the prepared The XRD pattern of Co-MOF shows four distinct diffraction peaks below 10° and around 15°~20°, which correspond to (200), (001), (201), (201 of Co-MOF, respectively. ) crystal plane, which proves the successful preparation of Co-MOF. Figure 2 shows the scanning electron microscope image of Co-MOF. The two-dimensional layered Co-MOF morphology is clearly visible in the figure.

Example 2:

The electrode material prepared in Example 1 was used for water electrolysis, and the specific steps were as follows: the Co-MOF modified electrode was placed in 0.1 mol/L KOH saturated with O2, the scanning speed was 5mV/s, and the rotation speed was 1600rpm; the potential window was 0 ~1.0V; select 1×10-3 sensitivity for OER performance test.

Comparative Example 1:

In step (2) of Example 1, the reaction time in the constant temperature oven was changed to 12h and 48h, and the remaining conditions were kept unchanged, so as to synthesize two other Co-MOF materials for OER performance test. The test method and test conditions are identical to those of Example 2. The test results show that the overpotential of Co-MOF prepared with a reaction time of 24 hours is 480mV at 10 mA/cm2, which is lower than that of the reaction time of 12h (570mV) and 48h (520mV). It shows that the OER performance of the Co-MOF electrode material prepared under the condition of hydrothermal reaction time of 24 hours is better.

Comparative Example 2:

The OER performance of the two electrode materials, Co-MOF and Cu-MOF, was compared. The preparation method of Cu-MOF was exactly the same as that of Co-MOF, except that the initial reactant was changed from cobalt acetate to copper acetate. The test method and test conditions are the same as those in Example 2. Figure 3 shows the LSV curves of the two electrode materials, Co-MOF and Co-MOF. It can be clearly seen from the figure that for the OER reaction, the overpotential of the Co-MOF electrode material at 10 mA/cm2 is 470 mV, which is obviously It is lower than 730mV of Cu-MOF, indicating that its electrocatalytic performance is obviously better than that of Cu-MOF electrode material. It shows that the selection of metal ions will have a certain influence in the process of MOF material synthesis. The two-dimensional layered Co-MOF electrode material prepared by the invention has good stability and good oxygen evolution reaction performance. The field of energy technology has broad application prospects.

Claims (5)

1. A preparation method and oxygen evolution performance research of a two-dimensional layered Co-MOF electric material are characterized by comprising the following main steps:

(1) accurately measuring 128mL of DMF (N, N-dimethylformamide), 8mL of ethanol and 8mL of deionized water in a 250mL beaker, sealing by using a disposable plastic film and a rubber band to prevent DMF and ethanol from volatilizing, weighing 0.4984g (3 mmol) of terephthalic acid (H2 BDC) after uniformly mixing, then adding 0.7472g (3 mmol) of cobalt acetate tetrahydrate (C4H6CoO4.4H2O) under the ultrasonic condition (40 KHz), and transferring to a hydrothermal kettle;

(2) and (3) placing the hydrothermal kettle in an oven for reaction, taking out the hydrothermal kettle which is cooled to room temperature after the reaction is finished, pouring out the generated metal organic framework, cooling and centrifuging for 2-3 times, scraping the residual solid in the centrifugal tube into a watch glass by using distilled water and a glass rod, drying in a constant-temperature oven at 60 ℃ to remove water, taking out the watch glass after the product is completely dried, grinding uniformly, and marking as Co-MOF.

2. The preparation method and the oxygen evolution performance research of the two-dimensional layered Co-MOF electric material according to claim 1, wherein the volume ratio of DMF, ethanol and deionized water in the step (1) is 16: 1: 1; the molar ratio of the organic ligand terephthalic acid to the tetrahydrate cobalt acetate is 1: 1.

3. the preparation method and the oxygen evolution performance research of the two-dimensional layered Co-MOF electric material according to claim 1, wherein the hydrothermal reaction temperature of the solution in the step (2) is 140 ℃; the reaction time was 12, 24, 48 hours.

4. The preparation method and the oxygen evolution performance research of the two-dimensional layered Co-MOF electric material according to claim 1, wherein the time for cooling the hydrothermal reaction kettle to room temperature in the step (2) is 8 ~ 10 hours.

5. The preparation method and the oxygen evolution performance research of the two-dimensional layered Co-MOF electric material according to claim 1, wherein the drying time in the oven at the constant temperature of 60 ℃ in the step (2) is 4 ~ 6 hours.

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