阅读说明：本技术 一种基于溶胶凝胶法的富氮石墨烯气凝胶负载单原子簇催化剂的普适性制备和应用 (Universal preparation and application of nitrogen-rich graphene aerogel supported monatomic cluster catalyst based on sol-gel method ) 是由 张小华 陈金华 洪敏� 于 2020-07-03 设计创作，主要内容包括：本发明公开了一种基于溶胶凝胶法的富氮石墨烯气凝胶负载单原子簇催化剂的普适性制备和应用。催化剂的制备包括以下步骤：1)将氰胺多聚体粉末在惰性气体氛中进行高温分解得到g-C<Sub>3</Sub>N<Sub>4</Sub>黄色粉末；2)将石墨粉进行多步氧化剥离处理制得石墨烯氧化物GO；3)GO、g-C<Sub>3</Sub>N<Sub>4</Sub>及大环有机金属化合物或含氮大环化合物形成的悬浮液经水热反应得到水凝胶；4)将水凝胶冷冻干燥后在惰性气氛中高温热解得到富氮石墨烯气凝胶负载单原子簇催化剂。运用本发明所得到的富氮石墨烯气凝胶负载的FeNx、CoNx、CuNx中的一种或一种以上原子簇催化剂在碱性溶液中对ORR或OER具有优异的催化活性和稳定性,在燃料电池、金属-空气电池及水电解中有着很好的应用前景。本发明操作工艺简单安全,成本低廉,具有可控制备、大量合成等优点,适合工业化生产和规模化应用。(The invention discloses universal preparation and application of a nitrogen-rich graphene aerogel load monatomic cluster catalyst based on a sol-gel method. The preparation of the catalyst comprises the following steps: 1) reacting cyanamideThe polymer powder is pyrolyzed in an inert gas atmosphere to obtain g-C 3 N 4 A yellow powder; 2) carrying out multi-step oxidation stripping treatment on graphite powder to prepare graphene oxide GO; 3) GO, g-C 3 N 4 And a suspension formed by a macrocyclic organic metal compound or a nitrogenous macrocyclic compound is subjected to a hydrothermal reaction to obtain hydrogel; 4) and freezing and drying the hydrogel, and then carrying out high-temperature pyrolysis in an inert atmosphere to obtain the nitrogen-rich graphene aerogel supported monatomic cluster catalyst. The nitrogen-enriched graphene aerogel loaded one or more than one atomic cluster catalyst of FeNx, CoNx and CuNx obtained by the invention has excellent catalytic activity and stability on ORR or OER in an alkaline solution, and has good application prospect in fuel cells, metal-air cells and water electrolysis. The method has the advantages of simple and safe operation process, low cost, controllable preparation, large-scale synthesis and the like, and is suitable for industrial production and large-scale application.)

1. A universal preparation method of nitrogen-rich graphene aerogel supported monatomic cluster catalyst based on a sol-gel method is characterized in that graphene and graphitized carbon nitride (g-C) are used₃N₄) Preparing nitrogen-enriched graphene aerogel serving as a carrier of the metal monatomic cluster;

2. a sol-gel method-based universal preparation method of nitrogen-rich graphene aerogel supported monatomic cluster catalyst is characterized in that the catalyst is uniformly supported on a nitrogen-rich graphene aerogel carrier in a monatomic cluster form;

3. a pervasive preparation method of nitrogen-rich graphene aerogel supported monatomic cluster catalyst based on a sol-gel method is characterized by comprising the following steps:

1)g-C₃N₄the preparation of (1): the dicyandiamide or the melamine powder is subjected to pyrolysis in an inert gas atmosphere such as nitrogen, argon or helium, the decomposition temperature is 300-900 ℃, and the decomposition time is 40 min-6 h. Cooling to obtain g-C₃N₄A yellow powder;

2) preparation of graphene oxide GO: carrying out multi-step oxidation stripping treatment on graphite powder, and carrying out acid pickling, water washing and drying to obtain graphene oxide GO;

3) preparing nitrogen-enriched graphene hydrogel: ultrasonically dispersing the prepared graphene oxide in ultrapure water uniformly, adding a macrocyclic organic metal source precursor or a nitrogen-containing macrocyclic compound (aza crown ether and macrocyclic polyamine) and a metal inorganic salt precursor and the prepared g-C₃N₄Ultrasonic, based on GO, g-C₃N₄And self-assembling and coordinating macrocyclic organic metal compound or nitrogenous macrocyclic compound to form uniform suspension, and then transferring the suspension into a high-temperature reaction kettle to perform hydrothermal reaction for a certain time to obtain nitrogen-rich graphene hydrogel;

4) preparing a nitrogen-enriched graphene aerogel supported monatomic cluster catalyst: and freeze-drying the hydrogel, and then performing high-temperature pyrolysis in an inert atmosphere to obtain the nitrogen-rich graphene aerogel supported monatomic cluster catalyst.

4. The preparation method of the nitrogen-enriched graphene aerogel supported monatomic cluster catalyst according to claim 3, characterized in that in the step 2), the preparation of graphene oxide GO is prepared by a multi-step oxidation exfoliation method of graphite powder. The method comprises the following steps:

a) 1-20 mL of concentrated H₂SO₄、03 to 5g of K₂S₂O₈And 0.3 to 5g of P₂O₅And (3) fully mixing in an ice bath, adding 1-5 g of graphite powder into the mixed solution, and raising the temperature to 50-90 ℃ in an oil bath for pre-oxidation for 0.5-5 h. Then standing and cooling to room temperature, diluting with 0.3-1L of deionized water, filtering and collecting a solid product, continuously washing with deionized water to be neutral, and standing overnight and naturally drying for later use;

b) adding the solid product prepared in the step a) into concentrated H in 30-150 mL ice bath₂SO₄With concentrated H₃PO₄The mixed concentrated acid (volume ratio is 4-9: 1) is slowly added with 5-20 g of KMnO₄Further oxidizing and keeping the temperature below 20 ℃ for 0.2-1 h, then heating to 30-45 ℃ for reaction for 1-6 h, diluting with 250-1000 mL of deionized water after reaction, and cooling to room temperature;

c) using 10-30 mL of 30 wt% H₂O₂Processing unreacted KMnO in the solution of step b)₄Uniformly stirring until the reaction is finished, washing with a dilute HCl solution (1L), and then washing with deionized water until the reaction is neutral; and finally, carrying out vacuum drying to obtain the graphene oxide GO.

5. The preparation method of the nitrogen-enriched graphene aerogel supported monatomic cluster catalyst according to claim 3, characterized in that in step 3), the macrocyclic organometallic precursor is iron phthalocyanine, cobalt phthalocyanine or copper phthalocyanine; iron porphyrin, cobalt porphyrin or iron porphyrin; or a mixture of two thereof; or the nitrogen-containing macrocyclic compounds (azacrown ethers and macrocyclic polyamines) are mixed with iron nitrate, cobalt nitrate, copper nitrate or chloride, cobalt chloride, copper chloride or iron sulfate, cobalt sulfate, copper sulfate;

when the metal precursor is iron phthalocyanine or iron porphyrin or a nitrogen-containing macrocyclic compound (aza crown ether and macrocyclic polyamine) and ferric nitrate or ferric chloride or ferric sulfate, the obtained catalyst material is a nitrogen-rich graphene aerogel supported iron-nitrogen cluster catalyst;

when the metal precursor is cobalt phthalocyanine or cobalt porphyrin or a nitrogen-containing macrocyclic compound (aza crown ether and macrocyclic polyamine) and cobalt nitrate or cobalt ferric chloride or cobalt sulfate, the obtained catalyst material is a nitrogen-rich graphene aerogel supported cobalt-nitrogen atom cluster catalyst;

when the metal precursor is copper phthalocyanine or copper porphyrin or a nitrogen-containing macrocyclic compound (aza crown ether and macrocyclic polyamine) and copper nitrate or copper chloride or copper sulfate, the obtained catalyst material is a nitrogen-rich graphene aerogel supported copper nitrogen cluster catalyst;

when the metal precursor is an organic metal precursor mixture or a mixture of aza-crown ether, macrocyclic polyamine and metal inorganic salt, the obtained catalyst material is an atomic cluster catalyst of nitrogen-rich graphene aerogel supported mixed metal nitride.

6. The preparation of nitrogen-enriched graphene aerogel supported monatomic cluster catalyst according to claim 3, characterized in that in step 3), the preparation of nitrogen-enriched graphene hydrogel is carried out according to the following procedure:

adding 40 mg-0.5 g of GO prepared in the step 2) into 40-200 mL of ultrapure water for ultrasonic dispersion to obtain a yellow GO dispersion liquid; subsequently, an organometallic precursor or a nitrogen-containing macrocyclic compound (azacrown ether and macrocyclic polyamine) is combined with the metal inorganic salt precursor mixture and g-C₃N₄According to different GO: g-C₃N₄Adding metal precursors into GO dispersion liquid according to the mass ratio of 4:8:1, 3:6:1, 2:4:1, 1:2:1, 2:3:1 and 2:4.5:1, and carrying out ultrasonic treatment for 1-6 hours until the color of the solution changes from brown yellow to light green and finally to dark green. And then transferring the suspension into a proper high-temperature reaction kettle, carrying out hydrothermal treatment at 120-200 ℃ for 6-30 hours to obtain the nitrogen-rich graphene hydrogel.

7. The preparation method of the nitrogen-enriched graphene aerogel supported monatomic cluster catalyst according to claim 3, characterized in that in the step 4), the hydrogel obtained in the step 3) is freeze-dried for 24 hours; and then performing high-temperature pyrolysis for 1-4 h in nitrogen or argon or helium at the temperature of 500-950 ℃ to obtain the nitrogen-rich graphene aerogel supported monatomic cluster catalyst.

8. Nitrogen-enriched graphene aerogel supported monatomic cluster catalyst obtained by the method of any of claims 1-7.

9. The use of the nitrogen-enriched graphene aerogel supported monatomic cluster catalyst of claim 8, wherein: the nitrogen-rich graphene aerogel supported monatomic cluster catalyst is used for chemical reaction in an electrocatalytic alkaline solution and is used as an electrocatalyst.

10. Use according to claim 9, characterized in that: when the nitrogen-rich graphene aerogel supported monatomic cluster catalyst is a monatomic cluster catalyst containing one or more active sites of FeNx, CoNx and CuNx, the catalyst is used for catalyzing oxygen reduction (ORR) reaction of a fuel cell or a metal-air cell and OER reaction of electrolyzed water under an alkaline condition.

Technical Field

The invention belongs to the technical field of monatomic cluster catalyst synthesis, and particularly relates to a universal preparation method of a nitrogen-rich graphene aerogel supported monatomic cluster catalyst, the nitrogen-rich graphene aerogel supported monatomic cluster catalyst and application.

Background

The demand of human beings on energy is gradually increased, non-renewable energy sources such as petroleum are gradually exhausted, and the seeking of petroleum substitutes is a necessary requirement for realizing low-carbon economy and reducing environmental pollution. In recent years, with the development of technologies, renewable energy sources such as wind energy, hydroelectric energy, solar energy and the like are increasingly utilized. The key to the sustainable development and application of clean energy is the search for safe, reliable and efficient storage methods and efficient utilization technologies for renewable and sustainable energy. Currently, renewable energy conversion and storage systems such as fuel cells, metal-air batteries, and water electrolysis devices have thus received extensive attention and development. The retarded kinetics of the oxygen reduction (ORR) and Oxidation (OER) processes remain the biggest obstacles in the development and application of fuel cell, metal-air cell and electrolytic water technologies. The search for efficient, stable, low cost ORR and OER catalysts remains a vital task in developing energy conversion and storage technologies for fuel cells, metal-air cells, and electrolysis of water.

The method is widely researched and verified by scientific researchers: among the non-noble metal catalysts, metal nitrides (MNx) are the main active centers that generally exhibit high activity for ORR and OER processes. Extensive researchers are currently developing high performance ORR and OER catalysts by designing reasonable nanostructures and regulating sizes, mainly based on the inexpensive price of non-noble metals, abundant earth reserve resources.

Atomic scale catalysts have attracted considerable attention from researchers since 2011 billows the successful synthesis of iron-based single atom active site catalysts and the introduction of the concept of "single atom catalysts". On one hand, the atomic-scale catalyst can greatly improve the number of active sites and realize high atom utilization rate due to the completely exposed atoms, and on the other hand, the low-coordination unsaturated state of the atomic-scale catalyst and the enhanced interaction of a metal carrier can obviously improve the intrinsic activity of the active sites. Thus, scientists have recently vigorously conducted studies to regulate the activity and utilization of catalysts based on monatomic catalysts.

However, compared to monatomic catalysts, cluster catalysts are less of a scientific concern. The atomic cluster is formed by aggregating a small number of atoms, is larger than a single atom in size, and even reaches the nanometer level when the number of the aggregated atoms reaches a certain number. Clusters containing only a small number of atoms exhibit exceptional and unexpected performance due to high surface atomic ratios, nano-sized characteristics that are different from bulk catalysts, low catalyst usage and effective catalyst utilization. Reported research work has shown that gold atom cluster catalysts, platinum atom cluster catalysts, Fe cluster catalysts (C/TP-Fe700), and conix single cluster (C/P/2Co600), etc., all exhibit excellent catalytic activity in specific environments. However, the preparation of highly dispersed, highly active nitrogen-rich graphene aerogel supported MNx monatomic cluster catalysts by a simple and clean method suitable for industrial production and large-scale application without the use of surfactants remains a significant challenge.

Disclosure of Invention

The invention provides universal preparation and application of a nitrogen-rich graphene aerogel supported monatomic cluster catalyst based on a sol-gel method, the preparation method can be generally suitable for synthesis of various nitrogen-rich graphene aerogel supported monatomic cluster catalysts, and the preparation method has the advantages of simple and safe operation process, low cost, controllable preparation, large-scale synthesis and the like, and is suitable for industrial production and large-scale application. The nitrogen-rich graphene aerogel-loaded one or more than one atomic cluster catalyst of FeNx, CoNx and CuNx prepared by the method has excellent catalytic activity and stability on ORR or OER in an alkaline solution, and has good application prospects in fuel cells \ metal-air cells and water electrolysis.

The invention is mainly realized by adopting the following technical scheme:

1. a general preparation method of nitrogen-rich graphene aerogel supported monatomic cluster catalyst based on a sol-gel method is characterized by comprising the steps of preparing graphene and graphitized carbon nitride (g-C)₃N₄) Preparing nitrogen-enriched graphene aerogel serving as a carrier of the metal monatomic cluster;

2. a sol-gel method-based universal preparation method of nitrogen-rich graphene aerogel supported monatomic cluster catalyst is disclosed, wherein a catalyst active center is uniformly supported on a nitrogen-rich graphene aerogel carrier in a monatomic cluster form;

3. a universal preparation method of nitrogen-rich graphene aerogel supported monatomic cluster catalyst based on a sol-gel method comprises the following steps:

1)g-C₃N₄the preparation of (1): decomposing cyanamide polymer powder at high temperature in inert gas atmosphere, and cooling to obtain g-C₃N₄A yellow powder;

2) preparation of graphene oxide GO: carrying out multi-step oxidation stripping treatment on graphite powder, and carrying out acid pickling, water washing and drying to obtain graphene oxide GO;

3) preparing nitrogen-enriched graphene hydrogel: ultrasonically dispersing the prepared graphene oxide in ultrapure water uniformly, adding a macrocyclic organic metal source precursor or a nitrogen-containing macrocyclic compound (aza crown ether and macrocyclic polyamine) and a metal inorganic salt precursor and the prepared g-C₃N₄Ultrasonic, based on GO, g-C₃N₄And self-assembling and coordinating macrocyclic organic metal compound or nitrogenous macrocyclic compound to form uniform suspension, and then transferring the suspension into a high-temperature reaction kettle to perform hydrothermal reaction for a certain time to obtain nitrogen-rich graphene hydrogel;

4) preparing a nitrogen-enriched graphene aerogel supported monatomic cluster catalyst: and freeze-drying the hydrogel, and then performing high-temperature pyrolysis in an inert atmosphere to obtain the nitrogen-rich graphene aerogel supported monatomic cluster catalyst.

Preferably, in the step 1), the cyanamide polymer is dicyandiamide or melamine.

Preferably, in step 1), the inert gas is nitrogen or argon or helium.

Preferably, in the step 1), the decomposition temperature is 300-900 ℃, and the decomposition time is 40 min-6 h.

Preferably, in the step 2), the graphene oxide GO is prepared by a multi-step oxidation stripping method of graphite powder. The method comprises the following steps:

a) 1-20 mL of concentrated H₂SO₄0.3 to 5g of K₂S₂O₈And 0.3 to 5g of P₂O₅And (3) fully mixing in an ice bath, adding 1-5 g of graphite powder into the mixed solution, and raising the temperature to 50-90 ℃ in an oil bath for pre-oxidation for 0.5-5 h. Then standing and cooling to room temperature, diluting with 0.3-1L of deionized water, filtering and collecting a solid product, continuously washing with deionized water to be neutral, and standing overnight and naturally drying for later use;

b) adding the solid product prepared in the step a) into concentrated H in 30-150 mL ice bath₂SO₄With concentrated H₃PO₄The mixed concentrated acid (volume ratio is 4-9: 1) is slowly added with 5-20 g of KMnO₄Further oxidizing and keeping the temperature below 20 ℃ for 0.2-1 h, then heating to 30-45 ℃ for reaction for 1-6 h, diluting with 250-1000 mL of deionized water after reaction, and cooling to room temperature;

c) treating the unreacted KMnO in the solution in the step b) with 10-30 mL of 30 wt% H2O2₄Uniformly stirring until the reaction is finished, washing with a dilute HCl solution (1L), and then washing with deionized water until the reaction is neutral; and finally, carrying out vacuum drying to obtain the graphene oxide GO.

Preferably, in the step 3), the macrocyclic organic metal precursor is iron phthalocyanine, cobalt phthalocyanine or copper phthalocyanine; iron porphyrin, cobalt porphyrin or iron porphyrin; or a mixture of two thereof; or macrocyclic compounds containing nitrogen (aza crown ethers and macrocyclic polyamines) are mixed with iron nitrate, cobalt nitrate, copper nitrate or chloride, cobalt chloride, copper chloride or iron sulfate, cobalt sulfate, copper sulfate.

When the metal precursor is iron phthalocyanine or iron porphyrin or a nitrogen-containing macrocyclic compound (aza crown ether and macrocyclic polyamine) and ferric nitrate or ferric chloride or ferric sulfate, the obtained catalyst material is a nitrogen-rich graphene aerogel supported iron-nitrogen cluster catalyst;

when the metal precursor is cobalt phthalocyanine or cobalt porphyrin or a nitrogen-containing macrocyclic compound (aza crown ether and macrocyclic polyamine) and cobalt nitrate or cobalt ferric chloride or cobalt sulfate, the obtained catalyst material is a nitrogen-rich graphene aerogel supported cobalt-nitrogen atom cluster catalyst;

when the metal precursor is copper phthalocyanine or copper porphyrin or a nitrogen-containing macrocyclic compound (aza crown ether and macrocyclic polyamine) and copper nitrate or copper chloride or copper sulfate, the obtained catalyst material is a nitrogen-rich graphene aerogel supported copper nitrogen cluster catalyst;

when the metal precursor is an organic metal precursor mixture or a mixture of aza-crown ether, macrocyclic polyamine and metal inorganic salt, the obtained catalyst material is an atomic cluster catalyst of nitrogen-rich graphene aerogel loaded with mixed metal nitride;

preferably, in the step 3), the preparation of the nitrogen-enriched graphene hydrogel is performed according to the following process:

adding 40 mg-0.5 g of GO prepared in the step 2) into 40-200 mL of ultrapure water for ultrasonic dispersion to obtain a yellow GO dispersion liquid; subsequently, an organometallic precursor or a nitrogen-containing macrocyclic compound (azacrown ether and macrocyclic polyamine) is combined with the metal inorganic salt precursor mixture and g-C₃N₄According to different GO: g-C₃N₄Adding metal precursors into GO dispersion liquid according to the mass ratio of 4:8:1, 3:6:1, 2:4:1, 1:2:1, 2:3:1 and 2:4.5:1, and carrying out ultrasonic treatment for 1-6 hours until the color of the solution changes from brown yellow to light green and finally to dark green. And then transferring the suspension into a proper high-temperature reaction kettle, carrying out hydrothermal treatment at 120-200 ℃ for 6-30 hours to obtain the nitrogen-rich graphene hydrogel.

Preferably, in the step 4), the hydrogel prepared in the step 3) is subjected to freeze drying for 24 hours; and then performing high-temperature pyrolysis for 1-4 h in nitrogen or argon or helium at the temperature of 500-950 ℃ to obtain the nitrogen-rich graphene aerogel supported monatomic cluster catalyst.

4. The nitrogen-rich graphene aerogel supported monatomic cluster catalyst is prepared by the method. The nitrogen-enriched graphene aerogel loads a monatomic cluster catalyst with one or more than one active sites of monatomic cluster catalysts FeNx, CoNx and CuNx.

5. The nitrogen-enriched graphene aerogel supported FeNx, CoNx and CuNx monatomic cluster active site catalyst is used for chemical reaction in an electrocatalytic alkaline solution and is used as an electrocatalyst.

Preferably, the nitrogen-enriched graphene aerogel supported FeNx monatomic cluster active site catalyst is used for catalyzing the oxygen reduction (ORR) reaction of a fuel cell or a metal-air cell under alkaline conditions; the nitrogen-enriched graphene aerogel supported CoNx and CuNx single-atom cluster active site catalyst and one or more than one type of supported FeNx, CoNx and CuNx active sites are used for catalyzing oxygen reduction (ORR) reaction of a fuel cell or a metal-air cell and OER reaction of electrolyzed water under alkaline conditions.

Description of the drawings

FIG. 1 photograph of FeNx monatomic cluster nitrogen-rich graphene aerogel

FIG. 2 is an SEM photograph (a), a TEM photograph (b) and an HRTEM photograph (c) of Fenx-CN/g-GEL

FIG. 3 SEM and TEM images of CuNx-CN/g-GEL

Detailed Description

The following examples are given to illustrate the present invention in more detail, but do not limit the scope of the claims of the present invention.