Metal-organic carbon composite catalyst and synthesis method thereof

Abstract

The application provides a metal-organic carbon composite catalyst and a synthesis method thereof. The catalyst comprises metal and different doped N to form M-N-C atomic clusters with catalytic active sites and a porous organic carbon network serving as a fixing support. The preparation method comprises the following steps: dissolving a transition metal salt and terephthalic acid in N,N-dimethylformamide to prepare a metal organic framework; mixing resorcinol, a nitrogen-rich organic compound and the metal organic framework in deionized water, adding dropwise formaldehyde to prepare a mixed solution, and performing alkaline catalysis to prepare a three-dimensional organic framework gel; and then performing sealed standing, drying and aging, crushing, high-temperature carbonization and nitridation, and acid washing and drying to obtain the metal-organic carbon composite catalyst. When the catalyst is used as a cathode catalyst of a metal-air battery, the catalyst exhibits good oxygen reduction activity and charge-discharge stability, and the catalyst is environment-friendly, rich in resources, low in cost, high in yield and controllable in microstructure, and is an ideal electrocatalyst for a battery with air as a cathode reaction.

Description

Technical Field

[0001] This invention relates to the field of electrocatalyst preparation technology, specifically to a metal-organic carbon composite catalyst and its preparation method. Background Technology

[0002] A fuel cell is an energy conversion device that directly converts the chemical energy stored in fuel into electrical energy. The fuel cell power generation process does not involve a heat engine process and is not limited by the Carnot cycle. Most of the chemical energy of the fuel can be directly converted into electrical energy, with an energy conversion efficiency of 40-60%. Simultaneously, the reaction products of fuel cells are harmless substances such as water, producing almost no pollutants such as sulfur dioxide, nitrogen oxides, and suspended solids, and releasing no greenhouse gas carbon dioxide. This aligns with the current societal concept of low-carbon emission reduction and environmental protection, contributing to my country's goal of achieving carbon peaking and carbon neutrality. Furthermore, fuel cells have advantages such as requiring fewer auxiliary devices, operating silently, being easy and reliable to operate, and offering high flexibility, making them widely recognized as the preferred clean and efficient energy conversion technology in today's society. In recent years, they have received significant attention from governments and research institutions worldwide.

[0003] Currently, as one of the key materials for fuel cells, the material composition, preparation cost, electrocatalytic activity, and cell stability of electrocatalysts pose the biggest challenges to the commercialization of fuel cell technology. Pt-based catalysts, currently the most widely used, suffer from high fuel cell prices due to limited resources, high cost, and complex and demanding preparation processes, becoming a bottleneck restricting fuel cell commercialization. In recent years, non-precious metal catalysts have become a hot topic in this field of research and development. Non-precious metal oxygen reduction cathode catalysts mainly include transition metal cluster compounds, transition metal macrocyclic compounds, transition metal oxides, transition metal carbonitride compounds, and carbon-based composite materials. The better catalytic activity and lower price of non-precious metal catalysts make them a promising alternative to Pt-based catalysts. However, due to the high potential conditions under which fuel cells operate, non-precious metal materials are prone to side reactions leading to catalyst deactivation, and their long-term operational stability is still far from meeting practical application requirements. Therefore, to realize the commercial application of fuel cells, it is urgent to develop a highly active, highly stable, and inexpensive non-precious metal fuel cell cathode catalyst. Summary of the Invention

[0004] The purpose of this invention is to provide a metal-organic carbon composite catalyst; the metal-organic carbon gel material has a large specific surface area, a mesoporous structure suitable for mass transport and good electrical and thermal conductivity, and as a cathode catalyst for fuel cells, it exhibits good corrosion resistance, stability and oxygen reduction and oxygen evolution reaction activity.

[0005] Another objective of this invention is to provide a method for preparing a metal-organic carbon composite catalyst Y-NC@NCX (Y = Fe, Co, Ni, Cu, Zn, Zr, W, Ir, V, Cr, Mn, etc.).

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A metal-organic carbon composite catalyst comprises a metal and nitrogen atoms in different doped states forming mesoporous nucleus (MNC) clusters with catalytically active sites, and a porous organic carbon network providing fixation and support. The clusters contain metal atoms, nitrogen atoms, and carbon atoms, with carbon atoms being the most abundant. The catalyst has a mesoporous three-dimensional network structure; the catalyst particle size is 10-30 nm, and the specific surface area is 80-300 m² / g. 2 g -l The pore volume is 0.2-0.78 cm³. 3 g -1 The pore size distribution is 2-25 nm.

[0008] A method for preparing a metal-organic carbon composite catalyst mainly includes the preparation of a metal-organic framework, the preparation of a three-dimensional organic framework gel, high-temperature carbonitride doping, and grinding, cleaning and drying steps.

[0009] A method for preparing a metal-organic carbon composite catalyst includes the following steps:

[0010] (1) A metal-organic framework was prepared by dissolving a transition metal salt and terephthalic acid in N,N-dimethylformamide and reacting them by a solvothermal method.

[0011] (2) Resorcinol, nitrogen-rich organic matter and the metal-organic framework are mixed and dissolved in deionized water, and formaldehyde is added dropwise to prepare a mixed solution; the mixed solution is subjected to alkaline catalysis, heated and stirred to obtain a three-dimensional organic framework gel;

[0012] (3) The three-dimensional organic framework gel is sealed, left to stand, dried and aged, crushed and then subjected to high-temperature carbonization and nitriding treatment, followed by acid washing and drying to obtain a metal-organic carbon composite catalyst.

[0013] Preferably, the metal element in the transition metal salt in step (1) is one or more of the groups IVB, VB, VIB, VIIB, VIII, IB and IIB.

[0014] Preferably, the metallic element is Fe, Co, Ni, Cu, Zn, Ir, V, Cr, Mn, Zr, or W.

[0015] Preferably, the molar ratio of the transition metal salt and terephthalic acid in step (1) is 1:10-2:1.

[0016] Preferably, the nitrogen-rich organic compound is peptone, melamine, dimethylimidazole, o-phenylenediamine, dimethylamine, trimethylamine, triethanolamine, diethanolamine, azo dye, imidazole, or carbazole.

[0017] Preferably, in step (2), the molar ratio of resorcinol to formaldehyde is 1:2, the molar ratio of resorcinol to nitrogen-rich organic matter is 20:1, and the mass ratio of resorcinol to metal-organic framework is 3:1-10:1; the heating temperature is 20-80℃, and the stirring time is 1-24h.

[0018] Preferably, in step (3), the sealed static drying and aging time is 1-7 days, and the drying and aging temperature is 50-90℃; the conditions for high-temperature carbonization and nitriding are: temperature of 700-1100℃, treatment time of 2-10h, and purging to room temperature with inert gas; the acid washing uses 0.5-5M acid solution.

[0019] Preferably, the nitriding atmosphere for high-temperature carbonization and nitriding is NH3 / N2, NH3, CH3CN or HCN atmosphere, and the inert gas is nitrogen or Ar.

[0020] Preferably, the acid solution is nitric acid, hydrochloric acid, phosphoric acid, or sulfuric acid.

[0021] A metal-organic carbon composite catalyst can be used as a cathode catalyst for fuel cells.

[0022] This invention utilizes the confinement effect of a three-dimensional organic gel network to construct a highly dispersed metal-organic framework. Through metal-nitrogen chelation, nitrogen atoms are anchored in situ, achieving a dual doping effect of nitrogen and metal atoms. High-temperature carbonization of the three-dimensional organic gel constructs a three-dimensional porous nano-carbon network structure, resulting in a highly catalytically active, stable, highly porosity, and highly dispersed metal-organic carbon composite catalyst. When used as a cathode catalyst in a metal-air battery, it exhibits excellent oxygen reduction activity and charge-discharge stability. Furthermore, this catalyst is environmentally friendly, resource-rich, low-cost, and has a tunable microstructure, making it an ideal electrocatalyst for air-based cathode reactors.

[0023] The present invention has the following advantages and technical effects:

[0024] (1) The preparation method of the present invention is simple, the structure of the prepared material is easy to control, the cost is low and the yield is high, which is a green synthesis method that can be scaled up.

[0025] (2) This invention utilizes the three-dimensional organic gel mesh confinement effect to enhance the uniform dispersion of metal-organic frameworks in materials, thereby improving the porosity and structural stability of the materials.

[0026] (3) The material prepared by the present invention has a three-dimensional composite graphite carbon structure of metal-organic framework and metal-organic gel. The material has good electrical conductivity, high catalytic activity, good catalytic selectivity and stability. Attached Figure Description

[0027] Figure 1 The image shows the microstructure of the metal-organic carbon composite catalyst prepared in Example 1.

[0028] Figure 2 The figure shows the comparison curves of zinc-air cell discharge and power density of the metal-organic carbon composite catalyst prepared in Example 1 and the commercial Pt / C+RuO2 catalyst.

[0029] Figure 3 The zinc-air cell prepared in Example 1 using the organometallic carbon composite catalyst and the commercial Pt / C+RuO2 catalyst was tested at 10 mA / cm². -2 The specific discharge capacity comparison curve.

[0030] Figure 4 The above are comparison curves of the charge-discharge cycle of a zinc-air battery between the metal-organic carbon composite catalyst prepared in Example 1 and the commercial Pt / C+RuO2 catalyst.

[0031] Figure 5 A 10 mA cm⁻¹ zinc-air cell was prepared using the metal-organic carbon composite catalyst and a commercial Pt / C+RuO₂ catalyst as described in Example 1. -2 Cross-current charge-discharge cycle curve

[0032] Figure 6 Oxygen reduction polarization curves of the metal-organic carbon composite catalysts prepared in Examples 2, 3, and 4. Detailed Implementation

[0033] The present invention will be described in detail below through embodiments, but the present invention is not limited to the embodiments.

[0034] Example 1

[0035] A method for preparing a metal-organic carbon composite catalyst (Fe-NC@NCX):

[0036] (1) FeCl3·6H2O and terephthalic acid were mixed and dissolved in N,N-2-methylformamide. The metal-organic framework material was obtained by solvothermal reaction with FeCl3·6H2O and terephthalic acid in a molar ratio of 2:1.

[0037] (2) Resorcinol, peptone, and metal-organic framework materials are mixed and dissolved in deionized water, and formaldehyde is added dropwise to prepare a mixed solution; the molar ratio of resorcinol to formaldehyde is 1:2, the molar ratio of resorcinol to nitrogen-rich organic matter is 20:1, and the mass ratio of resorcinol to metal-organic framework is 3:1.

[0038] (3) Add ammonia water dropwise to the well-mixed solution;

[0039] (4) Heat and stir the solution to form a gel for 24 hours at a gelation temperature of 60°C.

[0040] (5) The obtained gel was sealed and placed in a vacuum drying oven for drying and aging for 7 days at a temperature of 60°C.

[0041] (6) High-temperature carbonization to prepare metal-organic carbon composite materials, the treatment gas is NH3, the carbonization temperature is 800℃, the heating rate is 10℃ / min, after reaching the target temperature, the temperature is held for 2h, and N2 gas is purged to room temperature.

[0042] (7) The impurities were washed away with 1M sulfuric acid solution and dried to obtain the Fe-NC@NCX composite catalyst.

[0043] Example 2

[0044] The difference from Example 1 is that the mass ratio of resorcinol to metal-organic framework is 10:1, and the resulting composite material is denoted as Fe-NC@NCX-1.

[0045] Example 3

[0046] The difference from Example 1 is that the molar ratio of FeCl3·6H2O and terephthalic acid is 1:10, the high-temperature nitriding atmosphere is nitrogen and NH3, and the final composite material is denoted as Fe-NC@NCX-2.

[0047] Example 4

[0048] The difference from Example 1 is that the mass ratio of resorcinol to metal-organic framework is 5:1, melamine is used to replace peptone in Example 1, the carbonization temperature is 700°C, and the holding time is 10h. The final composite material is denoted as Fe-NC@NCX-3.

[0049] Example 5

[0050] The difference from Example 1 is that dimethylimidazole was used to replace peptone in Example 1, the added alkaline solution was sodium hydroxide solution, the carbonization temperature was 900℃, and the final composite material was denoted as Fe-NC@NCX-4.

[0051] Example 6

[0052] The difference from Example 1 is that the solution was heated and stirred to form a gel for 1 hour, the gelation temperature was 80°C, the molar ratio of Co(NO3)2·6H2O to terephthalic acid was 1:10, the carbonization temperature was 1100°C, and the holding time was 5 hours. The final composite material obtained is denoted as Co-NC@NCX.

[0053] Example 7

[0054] The difference from Example 1 is that the molar ratio of NiCl2 to terephthalic acid is 1:10, and the resulting composite material is denoted as Ni-NC@NCX.

[0055] Example 8

[0056] The difference from Example 1 is that the molar ratio of CuCl2·2H2O and terephthalic acid is 1:10, o-phenylenediamine is used to replace peptone in Example 1, the solution is heated and stirred to form a gel for 7 hours, the gelation temperature is 40°C, and the final composite material is denoted as Cu-NC@NCX.

[0057] Example 9

[0058] The difference from Example 1 is that the molar ratio of ZnCl2 to terephthalic acid is 1:5, the gel drying and aging time is 1 day, the drying and aging temperature is 90°C, and the final composite material is denoted as Zn-NC@NCX.

[0059] Example 10

[0060] The difference from Example 1 is that the molar ratio of IrCl3·3H2O and terephthalic acid is 1:5, the gel drying and aging time is 5 days, the drying and aging temperature is 50°C, and the final composite material is denoted as Ir-NC@NCX.

[0061] Example 11

[0062] The difference from Example 1 is that the molar ratio of VCl3 to terephthalic acid is 1:6, and impurities are washed away with 0.5M nitric acid solution. The final composite material is denoted as V-NC@NCX.

[0063] Example 12

[0064] The difference from Example 1 is that the molar ratio of CrCl3·6H2O to terephthalic acid is 1:5, o-phenylenediamine is used to replace peptone in Example 1, and impurities are washed away with 2M phosphoric acid solution. The final composite material is denoted as Cr-NC@NCX.

[0065] Example 13

[0066] The difference from Example 1 is that the molar ratio of MnCl2·4H2O to terephthalic acid is 1:5, and the resulting composite material is denoted as Mn-NC@NCX.

[0067] Example 14

[0068] The difference from Example 1 is that the molar ratio of ZrCl4 to terephthalic acid is 1:10, melamine is used to replace peptone in Example 1, and impurities are washed away with 5M hydrochloric acid solution. The final composite material is denoted as Zr-NC@NCX.

[0069] Example 15

[0070] The difference from Example 1 is that the molar ratio of WCl6 to terephthalic acid is 1:10, and the resulting composite material is denoted as W-NC@NCX.

[0071] The microstructure of the Fe-NC@NCX composite material prepared in Example 1 is as follows: Figure 1 As shown in the figure, electrochemical tests revealed that the Fe-NC@NCX composite material exhibits high electrocatalytic activity. When installed in a zinc-air battery in a 6M potassium hydroxide electrolyte solution at a scan rate of 10 mV / s, the power density curve obtained is close to that of a battery assembled with a Pt / C+RuO2 catalyst. Figure 2 As shown. At 10mA cm -2 In the specific capacity curves obtained from the discharge test, the specific capacity of the Fe-NC@NCX composite material assembled battery is higher than that of the Pt / C+RuO2 catalyst battery, such as... Figure 3 As shown, the zinc-air cell charge-discharge curves of the Fe-NC@NCX composite catalyst are very close to those of the commercial Pt / C+RuO2 catalyst, and its performance at high current densities exceeds that of the commercial Pt / C+RuO2 catalyst. Figure 4 As shown. The zinc-air cell with Fe-NC@NCX composite catalyst has a 10 mA / cm² capacity. -2 The battery remained stable even after 675 hours of constant current charge-discharge cycling, far exceeding that of commercial Pt / C+RuO2 catalysts (40 hours of cycling), indicating that the Fe-NC@NCX composite catalyst has excellent battery cycling activity and stability.

[0072] The metal-organic carbon composite catalysts prepared in Examples 2, 3, and 4 all exhibited good oxygen reduction electrocatalytic activity. Figure 6 As shown.

Claims

1. A metal-organic carbon composite catalyst, characterized in that, The catalyst comprises metal M and N in different doped states forming MNC atomic clusters with catalytically active sites and a porous organic carbon network that provides fixation and support; the catalyst has a particle size of 10-30 nm and a specific surface area of ​​80-300 m². 2 g -l The pore volume is 0.2-0.78 cm³. 3 g -1 The pore size distribution is 2-25 nm; The method for preparing the metal-organic carbon composite catalyst includes the following steps: (1) A metal-organic framework was prepared by dissolving a transition metal salt and terephthalic acid in N,N-dimethylformamide and reacting them by a solvothermal method. (2) Resorcinol, nitrogen-rich organic matter and the metal-organic framework are mixed and dissolved in deionized water, and formaldehyde is added dropwise to prepare a mixed solution; the mixed solution is subjected to alkaline catalysis, heated and stirred to obtain a three-dimensional organic framework gel; (3) The three-dimensional organic framework gel is sealed, left to stand, dried and aged, crushed and then subjected to high-temperature carbonization and nitriding treatment, followed by acid washing and drying to obtain a metal-organic carbon composite catalyst.

2. The method for preparing the metal-organic carbon composite catalyst according to claim 1, characterized in that, Includes the following steps: (1) A metal-organic framework was prepared by dissolving a transition metal salt and terephthalic acid in N,N-dimethylformamide and reacting them by a solvothermal method. (2) Resorcinol, nitrogen-rich organic matter and the metal-organic framework are mixed and dissolved in deionized water, and formaldehyde is added dropwise to prepare a mixed solution; the mixed solution is subjected to alkaline catalysis, heated and stirred to obtain a three-dimensional organic framework gel; (3) The three-dimensional organic framework gel is sealed, left to stand, dried and aged, crushed and then subjected to high-temperature carbonization and nitriding treatment, followed by acid washing and drying to obtain a metal-organic carbon composite catalyst.

3. The method according to claim 2, characterized in that, The metal element in the transition metal salt in step (1) is one or more of the groups IVB, VB, VIB, VIIB, VIII, IB and IIB.

4. The method according to claim 3, characterized in that, The metallic elements are Fe, Co, Ni, Cu, Zn, Ir, V, Cr, Mn, Zr, and W.

5. The method according to claim 2, characterized in that, The molar ratio of the transition metal salt and terephthalic acid in step (1) is 1:10-2:

1.

6. The method according to claim 2, characterized in that, In step (2), the molar ratio of resorcinol to formaldehyde is 1:2, the molar ratio of resorcinol to nitrogen-rich organic matter is 20:1, and the mass ratio of resorcinol to metal-organic framework is 3:1-10:1; the heating temperature is 20-80℃, and the stirring time is 1-24h.

7. The method according to claim 2, characterized in that, In step (3), the sealing and static drying time is 1-7 days, and the drying temperature is 50-90℃; the conditions for high-temperature carbonization and nitriding are: temperature of 700-1100℃, treatment time of 2-10h, and purging to room temperature with inert gas or nitrogen; the acid washing uses 0.5-5M acid solution.

8. The method according to claim 7, characterized in that, The nitriding atmosphere for high-temperature carbonization and nitriding is NH3 / N2, NH3, CH3CN or HCN atmosphere, and the inert gas is Ar.

9. The method according to claim 7, characterized in that, The acid solution is nitric acid, hydrochloric acid, phosphoric acid, or sulfuric acid.

10. The application of the metal-organic carbon composite catalyst according to claim 1, characterized in that, The aforementioned metal-organic carbon composite catalyst can be used as a cathode catalyst for fuel cells.

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