A ZIF-derived composite bifunctional electrocatalytic material and its preparation method and application

Abstract

A ZIF-derived composite bifunctional electrocatalytic material, its preparation method, and its applications are disclosed, belonging to the field of new energy materials. This material is synthesized by stirring at room temperature with the organic ligand 2-methylimidazole and metal sources zinc nitrate, cobalt nitrate, and iron acetylacetone, as well as the sulfur source thioacetamide. The preparation method is simple, and the reaction conditions are mild and environmentally friendly. Under the synergistic effect of the bimetallic alloy and heteroatoms, this catalytic material exhibits highly efficient oxygen reduction and oxygen evolution electrochemical performance. When assembled into a zinc-air battery, it has an open-circuit voltage of 1.48V, and the battery exhibits minimal degradation after 500 cycles, comparable to commercial materials.

Description

Technical Field

[0001] This invention belongs to the field of new energy materials, specifically relating to a method for preparing ZIF-L-derived transition metal and heteroatom-doped composite carbon materials under different iron sources and their application in zinc-air batteries. Background Technology

[0002] With the rapid development of modern society, the increasing energy consumption has led to resource depletion and environmental problems that are drawing growing attention. Currently, 70% of global energy consumption is provided by non-renewable fossil fuels. While the energy released from their combustion can meet a large portion of human needs, fossil fuels, while promoting socio-economic development, have also caused serious environmental problems. Therefore, researchers are dedicated to developing more efficient, renewable, and clean energy conversion and storage devices. Electrochemical technology, an effective means of converting renewable energy from chemical energy to electrical energy, is considered one of the most promising energy technologies. Among these, rechargeable zinc-air batteries (ZABs) combine the key characteristics of secondary batteries and fuel cells, meeting both the high energy density requirements of power batteries and the high safety and economic efficiency requirements of consumer batteries. The performance of rechargeable ZABs mainly depends on the oxygen reduction reaction (ORR) at the cathode during discharge and the oxygen evolution reaction (OER) at the anode during charging. However, at the complex liquid-gas-solid three-phase interface, the ORR / OER reaction kinetics are slow and the durability is poor. Rechargeable ZABs still suffer from low round-trip efficiency and poor stability. Based on the above analysis, designing and using highly efficient bifunctional electrocatalysts that exhibit both ORR and OER catalytic behaviors and are highly adaptable to the environment is key to realizing high-performance zinc-air batteries.

[0003] To develop efficient and low-cost ORR / OER bifunctional catalysts, an effective approach is to assemble transition metal and heteroatom-doped carbon-based catalysts. Zeolite imidazolium ester frameworks (ZIFs) are novel metal-organic frameworks (MOFs) that utilize the coordination of metal ions with imidazolium to form complex structures, exhibiting characteristics such as large specific surface area and high porosity. Their pyrolysis product is MNC, and due to their high atomic utilization and metal catalytic centers, they are frequently used as catalytic materials. However, the structure and morphology of ZIFs are significantly influenced by their synthesis conditions. Surfactants are often added to control their growth direction, forming ZIF precursors with controllable morphologies. Iron and cobalt are the most commonly used transition metals for preparing bifunctional catalysts, and different coordination structures and even different types of substances can be obtained under the influence of different metal sources. The types of these derived substances determine the catalytic performance of the material. Among them, the synergistic effect between Fe and Co in FeCo alloys provides a large number of binary active centers and electronic valence states, which can promote the formation of ORR active sites. However, the OER activity of most alloy catalysts is insufficient for their application in rechargeable zinc-air batteries. OER activity can be improved by adjusting the structure and charge distribution of carbon materials through heteroatom doping (such as B, N, P, S, and Se). Therefore, well-ordered precursors with controllable morphology can be synthesized, the effects of different iron sources on the morphology of ZIF material derivatives can be explored, and the bifunctionality of catalytic materials can be enhanced by combining transition metals with heteroatom-doped carbon substrates. Summary of the Invention

[0004] In response to the research needs in this field, the present invention aims to provide a bimetallic alloy / N,S co-doped carbon material derived from ZIF under different iron sources to improve the catalytic performance of the catalyst and to solve the problem of slow air cathode kinetics in zinc-air batteries.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing a ZIF-derived composite bifunctional electrocatalytic material involves stirring an aqueous solution of zinc nitrate and dimethylimidazole at room temperature to obtain ZIF-L, then adding different iron sources and heteroatom dopants to form a precursor, and finally obtaining the final product through high-temperature pyrolysis. The specific steps are as follows:

[0007] (1) Dissolve zinc nitrate in water to obtain solution A, dissolve 2-methylimidazole and surfactant P123 in water to obtain solution B, mix A and B and stir, filter, wash and dry the resulting precipitate to obtain ZIF-L;

[0008] (2) Add cobalt nitrate and iron acetylacetone to water and stir until uniform. Add ZIF-L obtained in step (1) and stir for 10 min. Then add a mixed solution of 2-methylimidazole and thioacetamide, stir, filter, wash and dry to obtain CoFe(acac)3-ZIF-L / S precursor.

[0009] (3) The obtained precursor was pyrolyzed under an inert atmosphere to obtain the final composite material Co-Co. 0.7 Fe 0.3 / S@NC.

[0010] In step (1), the molar ratio of zinc nitrate to 2-methylimidazole is 2:16, and the molar ratio of P123 to zinc nitrate is 0.0005-0.002:1, preferably 0.001:1.

[0011] In step (2), the molar ratio of cobalt nitrate to iron acetylacetone is 1:(0.1-0.3), preferably 1:0.2; the molar ratio of ZIF-L to cobalt nitrate is (0.5-2):1, preferably 1-1.5:1; the molar ratio of cobalt nitrate to 2-methylimidazole is 1:8; and the molar ratio of cobalt nitrate to thioacetamide is 1:0.8.

[0012] Preferably, the stirring time in steps (1) and (2) is 4 hours.

[0013] Preferably, the pyrolysis temperature in step (3) is 900℃, the heating rate is 5℃ / min, and the holding time is 2h.

[0014] The application of a ZIF-derived composite bifunctional electrocatalytic material obtained in this invention, and ZIF-L-derived Co-Co 0.7 Fe 0.3 The / S@NC composite material was used as a cathode catalyst in a zinc-air battery to prepare a working electrode for electrocatalyzing the reduction reaction of O2 and H2O and the precipitation of O2.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] (1) In this invention, surfactant P123 can regulate the morphology of ZIF, and the introduction of iron acetylacetone promotes the formation of Co. 0.7 Fe 0.3 Alloy formation.

[0017] (2) The catalyst of the present invention exhibits excellent oxygen reduction performance, with a half-wave potential of 0.9 V vs. RHE for the oxygen reduction reaction. Nitrogen-doped carbon materials derived from the zeolite imidazole framework can improve the stability and conductivity of the materials.

[0018] (3) The composite material preparation process of the present invention is simple and mild. The zinc-air battery assembled as an air cathode exhibits a high open-circuit voltage, good cycle stability and considerable power density, showing certain practical application potential. Attached Figure Description

[0019] Figure 1 Scanning electron microscope image of ZIF-L in this invention;

[0020] Figure 2 X-ray powder diffraction patterns of the samples prepared in Example 1 and Comparative Examples 1-2 of this invention;

[0021] Figure 3 Linear sweep voltammetric curves of the samples prepared in Examples 1-3 of this invention under alkaline conditions (a-0.1M KOH, b-1M KOH) for electrocatalytic oxygen reduction (a) and oxygen evolution (b);

[0022] Figure 4 Linear sweep voltammetric curves of electrocatalytic oxygen reduction (a) and oxygen evolution (b) of the samples prepared in Example 1 and Comparative Examples 1-3 of this invention under alkaline conditions (a-0.1M KOH, b-1M KOH); Figure 5 The open-circuit voltage curve (a), polarization curve, power density curve (b), and cycle stability (c) of the zinc-air battery samples prepared in Example 1 and Comparative Example 3 of this invention under alkaline conditions (6M KOH + 0.2M Zn(CH3COO)2). Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and examples, but the scope of protection of the present invention is not limited to the scope of protection of the examples.

[0024] Example 1:

[0025] (1) Dissolve 2 mmol Zn(NO3)2·6H2O in 40 ml of water to form solution A, dissolve 16 mmol 2-methylimidazole and 0.002 mmol P123 in an equal amount of water to form solution B, then mix solutions A and B and stir for 4 h, filter the resulting product and dry it in a vacuum oven at 70 °C for 12 h to obtain ZIF-L;

[0026] (2) Weigh 1 mmol Co(NO3)2·6H2O and 0.2 mmol Fe(acac)3 and dissolve them in 20 ml of water. After stirring evenly, add 1 mmol ZIF-L and stir for 10 min. Then add 20 ml of an aqueous solution of 8 mmol 2-methylimidazole and 0.8 mmol thioacetamide. Filter the obtained product and dry it in a vacuum oven at 60 °C for 12 h to obtain the precursor CoFe(acac)3-ZIF-L / S.

[0027] (3) The precursor CoFe(acac)3-ZIF-L / S was pyrolyzed under an argon atmosphere at a heating rate of 5℃ / min. After holding at 900℃ for 2 hours, Co-Co was obtained. 0.7 Fe 0.3 / S@NC composite materials.

[0028] Example 2:

[0029] (1) Same as step (1) in Example 1;

[0030] (2) Weigh 1 mmol Co(NO3)2·6H2O and 0.2 mmol Fe(acac)3 and dissolve them in 20 ml of water. After stirring evenly, add 0.5 mmol ZIF-L and stir for 10 min. Then add 20 ml of an aqueous solution of 8 mmol 2-methylimidazole and 0.8 mmol thioacetamide. Filter the obtained product and dry it in a vacuum oven at 60 °C for 12 h to obtain the precursor CoFe(acac)3-ZIF-L / S-0.5;

[0031] (3) The precursor CoFe(acac)3-ZIF-L / S-0.5 was pyrolyzed under an argon atmosphere at a heating rate of 5℃ / min. After holding at 900℃ for 2 hours, Co-Co was obtained. 0.7 Fe 0.3 / S@NC-0.5 composite material.

[0032] Example 3:

[0033] (1) Same as step (1) in Example 1;

[0034] (2) Weigh 1 mmol Co(NO3)2·6H2O and 0.2 mmol Fe(acac)3 and dissolve them in 20 ml of water. After stirring evenly, add 1.5 mmol ZIF-L and stir for 10 min. Then add 20 ml of an aqueous solution of 8 mmol 2-methylimidazole and 0.8 mmol thioacetamide. Filter the obtained product and dry it in a vacuum oven at 60 °C for 12 h to obtain the precursor CoFe(acac)3-ZIF-L / S-1.5.

[0035] (3) The precursor CoFe(acac)3-ZIF-L / S-1.5 was pyrolyzed under an argon atmosphere at a heating rate of 5℃ / min. After holding at 900℃ for 2 hours, Co-Co was obtained. 0.7 Fe 0.3 / S@NC-1.5 composite material.

[0036] Comparative Example 1:

[0037] (1) Same as step (1) in Example 1;

[0038] (2) Weigh 1 mmol Co(NO3)2·6H2O and 0.2 mmol ferric citrate and dissolve them in 20 ml of water. After stirring evenly, add 1 mmol ZIF-L and stir for 10 min. Then add 20 ml of an aqueous solution of 8 mmol 2-methylimidazole and 0.8 mmol thioacetamide. Filter the obtained product and dry it in a vacuum oven at 60 °C for 12 h to obtain the precursor Co(NMS)Fe-ZIF-L / S.

[0039] (3) The pyrolysis process is the same as in Example 1, and the Co-FeS@NC composite material is obtained.

[0040] Comparative Example 2:

[0041] (1) Same as step (1) in Example 1;

[0042] (2) Weigh 1 mmol Co(NO3)2·6H2O and 0.2 mmol K3[Fe(CN)6] and dissolve them in 20 ml of water. After stirring evenly, add 1 mmol ZIF-L and stir for 10 min. Then add 20 ml of aqueous solution of 8 mmol 2-methylimidazole and 0.8 mmol thioacetamide. Filter the obtained product and dry it in a vacuum oven at 60 °C for 12 h to obtain the precursor CoFe(QHJ)-ZIF-L / S.

[0043] (3) The pyrolysis process is the same as in Example 1, and the Co / S@NC composite material is obtained.

[0044] Comparative Example 3:

[0045] 20wt% PtC.

[0046] Test Results

[0047] Figure 1 SEM results showed that the precursor was 3D hexagonal star-shaped after the addition of surfactant P123.

[0048] Figure 2 The XRD pattern in the image indicates that the broad peak at approximately 25° is attributed to graphitic carbon. When acetylacetone iron is used as the iron source, pyrolysis yields Co and Co. 0.7 Fe 0.3 The characteristic peaks proved the successful formation of the bimetallic alloy and the nitrogen-carbon composite material; when iron citrate was used as the iron source, pyrolysis yielded Co and FeS; while when potassium ferricyanide was used as the iron source, only the characteristic peak of Co appeared.

[0049] Figure 3 The LSV curves show that ZIF-L exhibits the best catalytic activity at an addition level of 1 mmol.

[0050] Figure 4The LSV curves in the data show that the composite material Co-Co 0.7 Fe 0.3 / S@NC has the highest half-wave potential (0.9V vs. RHE) and the lowest overpotential (378mV vs. RHE);

[0051] Figure 5 This indicates that the composite material Co-Co 0.7 Fe 0.3 The / S@NC assembled zinc-air battery has an open-circuit voltage of 1.48V and a power density of 161mW / cm². -2 Furthermore, the degradation was not significant after 500 cycles (265h), and its performance was superior to that of zinc-air batteries using 20wt% commercial PtC and RuO2 as catalysts under the same conditions, indicating that the composite material has broad application prospects in the practical application of zinc-air batteries.

[0052] In summary, this invention utilizes surfactant P123 to induce a regular 3D hexagonal star shape in ZIF materials. By controlling the iron source, it was discovered that the metal source can influence the types of substances derived from ZIF materials, resulting in Co-Co... 0.7 Fe 0.3 Due to the synergistic effect between the alloy and the heteroatom-doped carbon substrate, the / S@NC composite material exhibits excellent oxygen reduction and oxygen evolution performance under alkaline conditions. As an air cathode, the zinc-air battery also shows good cycle stability and has certain practical application potential.

[0053] The above content is only a preferred embodiment of the present invention and is not intended to limit the implementation of the present invention. Any other changes, modifications, evolutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a ZIF-derived composite bifunctional electrocatalytic material, characterized in that, The specific steps are as follows: (1) Dissolve zinc nitrate in water to obtain solution A, dissolve 2-methylimidazole and surfactant P123 in water to obtain solution B, mix and stir A and B at room temperature, filter, wash and dry the resulting precipitate to obtain ZIF-L; (2) Add cobalt nitrate and iron acetylacetone to water and stir until uniform. Add ZIF-L obtained in step (1) and stir for 10 min. Then add a mixed solution of 2-methylimidazole and thioacetamide, stir, filter, wash and dry to obtain CoFe(acac)3-ZIF-L / S precursor. (3) The obtained precursor was pyrolyzed under an inert atmosphere to obtain the final composite material Co-Co. 0.7 Fe 0.3 / / N,S co-doped carbon materials; In step (1), the molar ratio of zinc nitrate to 2-methylimidazole is 2:16, and the molar ratio of P123 to zinc nitrate is 0.0005-0.002:

1. The molar ratio of cobalt nitrate to iron acetylacetone in step (2) is 1:(0.1-0.3).

2. The method according to claim 1, characterized in that, The molar ratio of P123 to zinc nitrate is 0.001:

1.

3. The method according to claim 1, characterized in that, In step (2), the molar ratio of cobalt nitrate to iron acetylacetone is 1:0.2, the molar ratio of ZIF-L to cobalt nitrate is (0.5-2):1, the molar ratio of cobalt nitrate to 2-methylimidazole is 1:8, and the molar ratio of cobalt nitrate to thioacetamide is 1:0.

8.

4. The method according to claim 3, characterized in that, The molar ratio of ZIF-L to cobalt nitrate is 1-1.5:

1.

5. The method according to claim 1, characterized in that, The stirring time in steps (1) and (2) is 4 hours.

6. The method according to claim 1, characterized in that, The pyrolysis temperature in step (3) is 900 ℃ and the holding time is 2 h; the inert atmosphere in step (3) is argon.

7. The ZIF-derived composite bifunctional electrocatalytic material prepared according to any one of claims 1-6.

8. The application of the ZIF-derived composite bifunctional electrocatalytic material prepared according to any one of claims 1-6 as a cathode catalyst in the preparation of a working electrode for a zinc-air battery.

9. The application according to claim 8, used for the electrocatalytic reduction reaction of O2 and H2O and the precipitation of O2.

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