CN109037703A - The preparation method and its application in zinc and air cell that a kind of surface has the bifunctional electrocatalyst of the fine nanometer package assembly of fold - Google Patents

Abstract

The invention discloses a preparation method of a bifunctional electrocatalyst with a wrinkled fine nanometer assembly structure on the surface and its application in a zinc-air battery, belonging to the technical field of zinc-air battery catalysts. The main points of the technical solution of the present invention are: introducing a wrinkle fine structure directing agent on the precursor MOF, introducing sulfur element while forming a wrinkle fine nano-assembly structure on the surface, and then introducing a nickel source dopant and a magnesium source dopant respectively, Bifunctional electrocatalysts with wrinkled fine nano-assembled structures on the surface were synthesized at room temperature. The nanometer electrocatalyst prepared by the invention has a surface wrinkled fine assembly structure and a hollow structure feature, which increases the specific surface area, thereby increasing the contact area between the catalyst and the electrolyte, and improving its electrocatalytic performance. The bifunctional electrocatalyst prepared in the present invention has better ORR and OER catalytic activity, and has better application prospects in zinc-air batteries.

Description

Preparation of a bifunctional electrocatalyst with wrinkled fine nano-assembly structure on the surface Preparation method and its application in zinc-air battery

technical field

The invention belongs to the technical field of zinc-air battery catalysts, and in particular relates to a preparation method of a bifunctional electrocatalyst with a wrinkled fine nanometer assembly structure on the surface and its application in zinc-air batteries.

Background technique

As a new type of energy conversion device, zinc-air battery has the advantages of environmental friendliness and high energy conversion efficiency. It has experimental applications in many fields and has attracted more and more attention. In addition, the zinc-air battery is small in size, large in charge capacity, small in mass, can work normally in a wide temperature range, has no corrosion, and works safely and reliably. Compared with the closed system lithium-ion battery, since the zinc-air battery is a semi-open system, the air in the environment is used to provide oxygen, which reduces the volume of the air electrode and increases the energy density. Therefore, zinc-air batteries have very good application prospects.

In the zinc-air battery, the key factor restricting its development is the electrode catalyst material. The catalyst is the core component of the zinc-air battery and is also a key material that determines the cost and performance of the battery. Common catalysts include noble metal catalysts and non-precious metal catalysts, but precious metals are scarce and expensive; and it is difficult for a single non-noble metal to exert its inherent catalytic activity. Therefore, developing a catalyst with low price and high performance is one of the important problems to be solved in the technical field of zinc-air battery catalyst synthesis.

Contents of the invention

The technical problem solved by the present invention is to provide a method for preparing a bifunctional electrocatalyst with a wrinkled fine nano-assembly structure on the surface. The bifunctional electrocatalyst prepared by this method can be used to catalyze the ORR and OER reactions of zinc-air batteries, effectively The electrochemical performance of Zn-air battery is improved.

In order to solve the above technical problems, the present invention adopts the following technical scheme, a preparation method of a bifunctional electrocatalyst with a wrinkled fine nano-assembly structure on the surface, which is characterized in that the specific process is: introducing a wrinkled fine structure directing agent on the precursor MOF, so that Sulfur is introduced while forming a wrinkled fine nano-assembly structure on its surface, and then a nickel source dopant and a magnesium source dopant are respectively introduced to synthesize a bifunctional electrocatalyst with a wrinkled fine nano-assembly structure on the surface at room temperature. The precursor MOF It is ZIF-67, the wrinkle fine structure directing agent is 2-mercaptobenzothiazole or 2-mercaptobenzimidazole, the nickel source dopant is nickel nitrate, and the magnesium source dopant is magnesium nitrate.

Further preferably, the preparation method of a bifunctional electrocatalyst having a wrinkled fine nano-assembled structure on the surface is characterized in that the specific steps are:

Step S1: Add 249mg of cobalt nitrate and 328mg of 2-methylimidazole into 50mL of methanol, stir and mix evenly, let stand at room temperature for 24h, wash with ethanol for several times and then vacuum dry to obtain the precursor MOF;

Step S2: Add the precursor MOF and wrinkle fine structure directing agent obtained in step S1 to ethanol and heat it in a water bath to reflux for 6-8 hours, centrifuge and wash with ethanol for several times, and then vacuum dry to obtain a wrinkled fine nano-assembly structure on the surface. purple sample;

Step S3: Add the purple sample with wrinkled fine nano-assembled structure on the surface obtained in step S2 and the nickel source dopant to ethanol and stir at room temperature for 6-8 hours, wash with ethanol for several times and then vacuum dry to obtain a hollow structure light green samples of

Step S4: Add the light green sample with a hollow structure obtained in Step S3 and the magnesium source dopant to ethanol and stir at room temperature for 6-8 hours, wash with ethanol for several times and then vacuum-dry, and then the dried sample In the air atmosphere, the temperature was raised to 200-300°C for 1-2h at a heating rate of 5-10°C/min, and a dodecahedron-shaped bifunctional electrocatalyst was obtained, which was hollow and had a wrinkled fine nano-assembly structure on the surface. The average particle size of the catalyst is 500nm, and the shell thickness is 15-20nm.

Further preferably, the mass ratio of the precursor MOF described in step S2 to the wrinkled fine structure directing agent is 2.5:1; the mass ratio of the purple sample with wrinkled fine nano-assembly structure on the surface described in step S3 to the nickel source dopant is 2.5:1; the mass ratio of the magnesium source dopant to the nickel source dopant in step S4 is 3:1.

The application of the bifunctional electrocatalyst with wrinkled fine nano-assembly structure on the surface of the present invention in catalyzing the ORR and OER reactions of zinc-air batteries, the wrinkled fine nano-assembly structure on the surface of the bifunctional electrocatalyst increases the specific surface area of the catalyst, and then The contact area between the catalyst and the electrolyte is increased, so that the catalyst can fully exert its activity. The bifunctional electrocatalyst contains metal Ni, Co and Mg at the same time and effectively exerts the synergistic effect between them, and has good ORR and OER catalytic activity. .

Compared with the prior art, the present invention has the following advantages:

1. The present invention has successfully synthesized a bifunctional electrocatalyst for zinc-air batteries with MOF as the precursor. The addition of thiol compounds makes it compete with the original ligand of the precursor MOF, changing the surface of the precursor MOF The local coordination environment makes the surface of the synthesized sample form a wrinkled fine nano-assembled structure, which increases the specific surface area of the bifunctional electrocatalyst and increases its contact area with the electrolyte, thereby improving the electrocatalysis of the catalyst. performance.

2. The introduction of the nickel source dopant, through its stronger interaction with the ligand, can produce an etching effect so that the catalyst forms a hollow structure, which also effectively increases the specific surface area of the material and increases the contact with the electrolyte. The contact area improves the electrocatalytic performance of the catalyst.

3. The specific addition method and ratio of magnesium make it replace part of the nickel and cobalt in the catalyst. On this basis, the synergistic effect between the various metal components is better, and the dispersion of the catalyst is improved, thereby The catalytic activity of the catalyst is improved.

4. In the present invention, MOF is used as the precursor to prepare the bifunctional electrocatalyst, which has a special preparation process. After the catalyst is calcined, its crystallinity is increased, its catalytic performance is also greatly improved, and its good shape is also maintained at the same time. It is a new synthesis method of bifunctional electrocatalyst for zinc-air battery.

Description of drawings

Fig. 1 is the SEM figure that embodiment 1 makes catalyst;

Fig. 2 is the SEM figure that embodiment 2 makes catalyst;

Fig. 3 is the SEM figure that comparative example 1 makes catalyst;

Fig. 4 is the ORR polarization curve of the prepared catalyst of embodiment 1, embodiment 2 and comparative example 1, comparative example 2 and comparative example 3;

Fig. 5 is the OER polarization curves of the catalysts prepared in Example 1, Example 2 and Comparative Example 1, Comparative Example 2 and Comparative Example 3.

Detailed ways

The above-mentioned contents of the present invention are described in further detail below through the embodiments, but this should not be interpreted as the scope of the above-mentioned themes of the present invention being limited to the following embodiments, and all technologies realized based on the above-mentioned contents of the present invention all belong to the scope of the present invention.

Electrochemical tests were carried out using half-cells of the Solartron 1287 (Solartron Analytical, England) type three-electrode system. The glassy carbon electrode coated with catalyst is the working electrode, wherein the catalyst is the target catalyst prepared in Example 1, Example 2, Comparative Example 1, Comparative Example 2 and Comparative Example 3, and the counter electrode and reference electrode are respectively 1 cm ² platinum sheet and Ag/AgCl saturated calomel electrode, the electrolyte is 0.1M KOH aqueous solution. In order to make the catalyst adhere well to the glassy carbon electrode, the glassy carbon electrode was washed with secondary water and dried at room temperature. The preparation steps of the thin-layer catalyst on the electrode are as follows: Take 5 mg of catalyst, add 0.5 mL of ethanol and 50 μL of perfluorosulfonic acid (PFSA) solution with a mass concentration of 5%, ultrasonically disperse for about 30 minutes, and use a micro-sampler to take 15 μL to disperse evenly through ultrasonic dispersion. The suspension was coated on a smooth glassy carbon electrode, and tested after drying at room temperature. The electrical performance test results are shown in Figure 4 and Figure 5.

Example 1

Step S1: Add 249mg of cobalt nitrate and 328mg of 2-methylimidazole into 50mL of methanol, stir and mix evenly, let stand at room temperature for 24h, wash with ethanol for several times and then vacuum dry to obtain the precursor MOF;

Step S2: Add 50 mg of the precursor MOF obtained in step S1 and 20 mg of the wrinkle fine structure directing agent 2-mercaptobenzothiazole into 25 mL of ethanol and heat it in a water bath to reflux for 7 hours, wash with ethanol for several times, and then vacuum dry to obtain the surface Purple sample with wrinkled fine nanoassembled structure;

Step S3: Add 50 mg of the purple sample with wrinkled fine nano-assembled structure on the surface obtained in step S2 and 20 mg of nickel nitrate as a nickel source dopant into 25 mL of ethanol and stir at room temperature for 7 h, centrifuge washing with ethanol for several times and then vacuum dry to obtain A light green sample with a hollow structure;

Step S4: Add the light green sample with a hollow structure obtained in step S3 and 60 mg of magnesium nitrate as a magnesium source dopant into 25 mL of ethanol and stir at room temperature for 7 h, wash with ethanol for several times and then vacuum-dry, and then dry The samples were calcined at 300°C for 1 h at a heating rate of 5°C/min in an air atmosphere, and finally a dodecahedron-shaped bifunctional electrocatalyst with a hollow surface and a wrinkled fine nano-assembly structure was obtained. The average particle size of the bifunctional electrocatalyst was The diameter is 500nm, and the shell thickness is 15~20nm, as shown in Figure 1.

Example 2

Step S1: Add 249mg of cobalt nitrate and 328mg of 2-methylimidazole into 50mL of methanol, stir and mix evenly, let stand at room temperature for 24h, wash with ethanol for several times and then vacuum dry to obtain the precursor MOF;

Step S2: Add 50 mg of the precursor MOF obtained in step S1 and 20 mg of the wrinkle fine structure directing agent 2-mercaptobenzimidazole into 25 mL of ethanol, heat it in a water bath to reflux for 7 hours, wash with ethanol for several times, and then vacuum dry to obtain the surface Purple sample with wrinkled fine nanoassembled structure;

Step S3: Add 50 mg of the purple sample with wrinkled fine nano-assembled structure on the surface obtained in step S2 and 20 mg of nickel nitrate as a nickel source dopant into 25 mL of ethanol and stir at room temperature for 7 h, centrifuge washing with ethanol for several times and then vacuum dry to obtain A light green sample with a hollow structure;

Step S4: Add the light green sample with a hollow structure obtained in step S3 and 60 mg of magnesium nitrate as a magnesium source dopant into 25 mL of ethanol and stir at room temperature for 7 h, wash with ethanol for several times and then vacuum-dry, and then dry The samples were calcined at 200 °C for 2 h at a heating rate of 10 °C/min in an air atmosphere, and finally a dodecahedron-shaped bifunctional electrocatalyst with a hollow surface and a wrinkled fine nano-assembly structure was obtained. The average particle size of the bifunctional electrocatalyst was The diameter is 500nm, and the shell thickness is 15~20nm, as shown in Figure 2.

Comparative example 1

Step S1: Add 249mg of cobalt nitrate and 328mg of 2-methylimidazole into 50mL of methanol, stir and mix evenly, let stand at room temperature for 24h, wash with ethanol for several times and then vacuum dry to obtain the precursor MOF;

Step S2: Add 50 mg of the precursor MOF obtained in step S1 and 20 mg of the nickel source dopant nickel nitrate into 25 mL of ethanol and stir at room temperature for 7 h, centrifuge and wash with ethanol for several times and then vacuum dry to obtain a light green sample;

Step S3: Add the light green sample obtained in step S2 and 60 mg of magnesium nitrate as a magnesium source dopant into 25 mL of ethanol and stir for 7 hours at room temperature, wash with ethanol for several times and then vacuum-dry, then place the dried sample in air In the atmosphere, the temperature was raised to 300° C. for 1 h at a heating rate of 5° C./min and calcined for 1 h, and finally the target catalyst with a smooth surface and a hollow dodecahedral structure was obtained, as shown in FIG. 3 .

Comparative example 2

Step S1: Add 249mg of cobalt nitrate and 328mg of 2-methylimidazole into 50mL of methanol, stir and mix evenly, let stand at room temperature for 24h, wash with ethanol for several times and then vacuum dry to obtain the precursor MOF;

Step S2: Add 50 mg of the precursor MOF obtained in step S1 and 20 mg of the wrinkle fine structure directing agent 2-mercaptobenzothiazole into 25 mL of ethanol and heat it in a water bath to reflux for 7 hours, wash with ethanol for several times, and then vacuum dry to obtain the surface Purple sample with wrinkled fine nanoassembled structure;

Step S3: Add the purple sample with wrinkled fine nano-assembled structure on the surface obtained in step S2 and 60 mg of magnesium nitrate as a magnesium source dopant into 25 mL of ethanol and stir at room temperature for 7 h, centrifuge and wash with ethanol for several times, then vacuum-dry, and then The dried sample was calcined in an air atmosphere at a rate of 5 °C/min to 300 °C for 1 h, and finally a solid dodecahedron-shaped target catalyst with a fine nano-assembly structure on the surface was obtained.

Comparative example 3

Step S1: Add 249mg of cobalt nitrate and 328mg of 2-methylimidazole into 50mL of methanol, stir and mix evenly, let stand at room temperature for 24h, wash with ethanol for several times and then vacuum dry to obtain the precursor MOF;

Step S2: Add 50 mg of the precursor MOF obtained in step S1 and 20 mg of the wrinkle fine structure directing agent 2-mercaptobenzothiazole into 25 mL of ethanol and heat it in a water bath to reflux for 7 hours, wash with ethanol for several times, and then vacuum dry to obtain the surface Purple sample with wrinkled fine nanoassembled structure;

Step S3: Add 50 mg of the purple sample with wrinkled fine nano-assembled structure on the surface obtained in step S2 and 20 mg of nickel nitrate as a nickel source dopant into 25 mL of ethanol and stir at room temperature for 7 h, centrifuge washing with ethanol for several times and then vacuum dry to obtain Target catalyst without magnesium component.

The bifunctional electrocatalyst for the zinc-air battery prepared by the invention has good catalytic activity for ORR and OER. It can be seen from the electrical performance test results in Figure 4 and Figure 5 that the bifunctional electrocatalysts prepared in Example 1 and Example 2 with the introduction of wrinkled fine structure directing agents have larger limiting current densities and half-wave potentials. The comparative examples show that compared with the catalysts without wrinkle fine nanostructure or without nickel source dopant or without magnesium source dopant, the bifunctional electrocatalysts prepared in Examples 1~2 have the best bifunctional catalytic activity ; On the one hand, the wrinkled fine nano-assembled structure on the surface of the bifunctional electrocatalyst increases the specific surface area of the catalyst, thus increasing the contact area between the catalyst and the electrolyte, so that the catalyst can fully exert its activity; on the other hand, the bifunctional electrocatalyst simultaneously Contains metals Ni, Co and Mg and effectively exerts the synergistic effect between them. The bifunctional electrocatalyst prepared by the invention with a wrinkled fine nanometer assembly structure on the surface has excellent electrocatalytic activity performance, and is a zinc-air battery catalyst with broad application prospects.

The above embodiments have described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What are described in the above embodiments and description are only to illustrate the principles of the present invention. Without departing from the scope of the principle of the present invention, there will be various changes and improvements in the present invention, and these changes and improvements all fall within the protection scope of the present invention.

Claims (4)

1. the preparation method that a kind of surface has the bifunctional electrocatalyst of the fine nanometer package assembly of fold, it is characterised in that tool Body process are as follows: introduce fold fine structure directed agents on presoma MOF, its surface is made to form the fine nanometer package assembly of fold While introduce element sulphur, then introduce nickel source dopant and magnesium source doping agent respectively, synthetic surface has fold essence at normal temperature The bifunctional electrocatalyst of thin nanometer package assembly, wherein presoma MOF is ZIF-67, and fold fine structure directed agents are 2- mercapto Base benzothiazole or 2-mercaptobenzimidazole, nickel source dopant are nickel nitrate, and magnesium source doping agent is magnesium nitrate.

2. the preparation side that surface according to claim 1 has the bifunctional electrocatalyst of the fine nanometer package assembly of fold Method, it is characterised in that specific steps are as follows:

Step S1: 249mg cobalt nitrate and 328mg 2-methylimidazole are added in 50mL methanol and are uniformly mixed, room temperature For 24 hours, with ethyl alcohol centrifuge washing, vacuum drying obtains presoma MOF to lower standing afterwards for several times；

Step S2: presoma MOF and fold fine structure directed agents that step S1 is obtained are added in ethyl alcohol and pass through water-bath It is heated to 6 ~ 8h of back flow reaction, repeatedly vacuum drying obtains surface with the fine nanometer assembling knot of fold afterwards with ethyl alcohol centrifuge washing The purple sample of structure；

Step S3: there is the purple sample of the fine nanometer package assembly of fold and nickel source dopant to add the surface that step S2 is obtained Enter into ethyl alcohol and stir under room temperature 6 ~ 8h, repeatedly vacuum drying obtains having the shallow of hollow structure afterwards with ethyl alcohol centrifuge washing Green sample；

Step S4: by the obtained light green color sample with hollow structure of step S3 and magnesium source doping agent be added in ethyl alcohol and in Stir 6 ~ 8h under room temperature, be repeatedly dried in vacuo afterwards with ethyl alcohol centrifuge washing, then by the sample after drying in air atmosphere with 5 ~ The heating rate of 10 DEG C/min is warming up to 200 ~ 300 DEG C of 1 ~ 2h of calcining, finally obtains hollow and surface with the fine nanometer of fold The dodecahedron shape bifunctional electrocatalyst of package assembly, the average grain diameter of the bifunctional electrocatalyst are 500nm, shell thickness For 15 ~ 20nm.

3. the preparation side that surface according to claim 2 has the bifunctional electrocatalyst of the fine nanometer package assembly of fold Method, it is characterised in that: the mass ratio of presoma MOF described in step S2 and fold fine structure directed agents is 2.5:1；Step S3 Described in surface have the fine nanometer package assembly of fold purple sample and nickel source dopant mass ratio be 2.5:1；Step The mass ratio of the agent of magnesium source doping described in S4 and nickel source dopant is 3:1.

4. surface made from method described in any one of -3 has the fine nanometer package assembly of fold according to claim 1 Application of the bifunctional electrocatalyst in catalysis zinc and air cell ORR and OER reaction, the fold on bifunctional electrocatalyst surface are fine Nanometer package assembly increases the specific surface area of catalyst, and then increases the contact area of catalyst and electrolyte, makes to be catalyzed Agent fully plays its activity, contains W metal, Co and Mg in bifunctional electrocatalyst simultaneously and has effectively played between them Synergistic effect, have good ORR and OER catalytic activity.