阅读说明：本技术 一种基于四-β-(4-醛基苯氧基)酞菁钴气凝胶制备的氧还原催化剂及其制备方法 (Oxygen reduction catalyst prepared based on tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine aerogel and preparation method thereof ) 是由 左霞 付媛媛 于越 于 2018-12-26 设计创作，主要内容包括：本发明涉及催化剂制备技术领域,提供了一种基于四-β-(4-醛基苯氧基)酞菁钴气凝胶制备氧还原催化剂的方法：(1)将四-β-(4-醛基苯氧基)酞菁钴、有机溶剂和醋酸-富氨基有机物混合液混合,得到水凝胶；(2)将步骤(1)所得水凝胶浸于水中去除多余溶剂,取出水凝胶后再浸于氧化石墨烯溶液或多壁碳纳米管溶液中进行吸附,得到复合水凝胶；(3)将步骤(2)所得复合水凝胶进行冷冻干燥,得到复合气凝胶；(4)在保护气氛下,将步骤(3)所得复合气凝胶进行高热处理,得到氧还原催化剂。本发明还提供了所述方法得到的氧还原催化剂,同时包含N、C和Co,原料易得,易于实施。本发明产品具有优异的电化学性能和催化性能。(The invention relates to the technical field of catalyst preparation, and provides a method for preparing an oxygen reduction catalyst based on tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine aerogel, which comprises the following steps: (1) mixing tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine, an organic solvent and an acetic acid-amino-rich organic matter mixed solution to obtain hydrogel; (2) soaking the hydrogel obtained in the step (1) in water to remove redundant solvent, taking out the hydrogel, and then soaking the hydrogel in a graphene oxide solution or a multi-walled carbon nanotube solution for adsorption to obtain a composite hydrogel; (3) freezing and drying the composite hydrogel obtained in the step (2) to obtain composite aerogel; (4) and (4) carrying out high-heat treatment on the composite aerogel obtained in the step (3) under a protective atmosphere to obtain the oxygen reduction catalyst. The invention also provides the oxygen reduction catalyst obtained by the method, which simultaneously contains N, C and Co, and has easily obtained raw materials and easy implementation. The product of the invention has excellent electrochemical performance and catalytic performance.)

1. A method for preparing an oxygen reduction catalyst based on tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine aerogel comprises the following steps:

(1) mixing tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine, an organic solvent and an acetic acid-amino-rich organic matter mixed solution to obtain hydrogel;

(2) soaking the hydrogel obtained in the step (1) in water to remove redundant solvent, taking out the hydrogel, and then soaking the hydrogel in a graphene oxide solution or a multi-walled carbon nanotube solution for adsorption to obtain a composite hydrogel;

(3) freezing and drying the composite hydrogel obtained in the step (2) to obtain composite aerogel;

(4) and (4) carrying out high-heat treatment on the composite aerogel obtained in the step (3) under a protective atmosphere to obtain the oxygen reduction catalyst.

2. The method as claimed in claim 1, wherein the ratio of the mass of the cobalt tetra-beta- (4-aldehyde phenoxy) phthalocyanine to the volume of the organic solvent in the step (1) is (0.01-0.5) g (1-5) mL.

3. The method according to claim 1 or 2, wherein the mass concentration of acetic acid in the acetic acid-amino-rich organic matter mixed solution in the step (1) is 0.1-5%, and the mass concentration of amino-rich organic matter is 1-5%;

the volume of the organic solvent and the mass ratio of the acetic acid-amino-rich organic matter mixed liquid are (1-3) ml and (2-10) g.

4. The method as claimed in claim 1, wherein the volume ratio of the organic solvent in the step (1) to the water in the step (2) is (1-5): 250-350).

5. The method as claimed in claim 1 or 4, wherein the time for soaking the hydrogel in water in the step (2) to remove the excessive solvent is more than or equal to 6 h.

6. The method according to claim 1, wherein the concentration of the graphene oxide solution or the multi-walled carbon nanotube solution in the step (2) is 1-10 mg/mL;

the volume ratio of the water to the graphene oxide solution or the multi-walled carbon nanotube solution in the step (2) is (250-350): 5-15.

7. The method according to claim 1 or 6, wherein the adsorption time in the step (2) is 1-10 h.

8. The method according to claim 1, wherein the temperature of the freeze drying in the step (3) is-60 to-50 ℃ and the time is 16 to 24 hours.

9. The method according to claim 1 or 8, wherein the temperature of the high-heat treatment in the step (4) is 600-900 ℃ and the time is 1-3 h.

10. An oxygen reduction catalyst obtainable by the process of any one of claims 1 to 9, comprising both N, C and Co.

Technical Field

The invention relates to the technical field of catalyst preparation, in particular to an oxygen reduction catalyst prepared based on tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine aerogel and a preparation method thereof.

Background

Fuel cells have many advantages such as cleanliness and high efficiency, and are considered to be one of the most promising green energy sources. However, the cathode oxygen reduction reaction, which is critical to fuel cells, has a loss of activation due to slower reaction kinetics, limiting the development of fuel cells.

However, the conventional fuel cell mostly uses a Pt-based catalyst, but Pt is expensive and scarce as a noble metal, and it is difficult to maintain the commercial mass production of the fuel cell.

Disclosure of Invention

The invention aims to provide a method for preparing an oxygen reduction catalyst based on aerogel and a product obtained by the method, and the oxygen reduction catalyst with excellent performance is obtained under the condition of avoiding using expensive and rare Pt.

In order to achieve the above object, the present invention provides the following technical solutions:

a method for preparing an oxygen reduction catalyst based on tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine aerogel comprises the following steps:

(1) mixing tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine, an organic solvent and an acetic acid-amino-rich organic matter mixed solution to obtain hydrogel;

(2) soaking the hydrogel obtained in the step (1) in water to remove redundant solvent, taking out the hydrogel, and then soaking the hydrogel in a graphene oxide solution or a multi-walled carbon nanotube solution for adsorption to obtain a composite hydrogel;

(3) freezing and drying the composite hydrogel obtained in the step (2) to obtain composite aerogel;

(4) and (4) carrying out high-heat treatment on the composite aerogel obtained in the step (3) under a protective atmosphere to obtain the oxygen reduction catalyst.

Preferably, the ratio of the mass of the tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine to the volume of the organic solvent in the step (1) is (0.01-0.5) g and (1-5) mL.

Preferably, in the step (1), the mass concentration of acetic acid in the acetic acid-amino-rich organic matter mixed solution is 0.1-5%, and the mass concentration of amino-rich organic matter is 1-5%;

the volume of the organic solvent and the mass ratio of the acetic acid-amino-rich organic matter mixed liquid are (1-3) ml and (2-10) g.

Preferably, the volume ratio of the organic solvent in the step (1) to the water in the step (2) is (1-5): 250-350).

Preferably, the time for soaking the hydrogel in water in the step (2) to remove the excessive solvent is more than or equal to 6 hours.

Preferably, the concentration of the graphene oxide solution or the multi-walled carbon nanotube solution in the step (2) is 1-10 mg/mL;

the volume ratio of the water to the graphene oxide solution or the multi-walled carbon nanotube solution in the step (2) is (250-350): 5-15.

Preferably, the adsorption time in the step (2) is 1-10 h.

Preferably, the temperature of the freeze drying in the step (3) is-60 to-50 ℃, and the time is 16 to 24 hours.

Preferably, the temperature of the high-heat treatment in the step (4) is 600-900 ℃, and the time is 1-3 hours.

The invention also provides an oxygen reduction catalyst obtained by the method in any one of the technical schemes, and the oxygen reduction catalyst simultaneously contains N, C and Co.

The invention provides a method for preparing an oxygen reduction catalyst based on tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine aerogel, which comprises the following steps: (1) mixing tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine, an organic solvent and an acetic acid-amino-rich organic matter mixed solution to obtain hydrogel; (2) soaking the hydrogel obtained in the step (1) in water to remove redundant solvent, taking out the hydrogel, and then soaking the hydrogel in a graphene oxide solution or a multi-walled carbon nanotube solution for adsorption to obtain a composite hydrogel; (3) freezing and drying the composite hydrogel obtained in the step (2) to obtain composite aerogel; (4) and (4) carrying out high-heat treatment on the composite aerogel obtained in the step (3) under a protective atmosphere to obtain the oxygen reduction catalyst. According to the method provided by the invention, the hole structure is generated through the aerogel, so that more active sites are exposed to ensure good electrocatalysis performance, Pt metal which is expensive and rare in storage amount is not required to be used, the material cost is low and easy to obtain, and the production cost is greatly reduced.

The invention also provides an oxygen reduction catalyst obtained by the method, which simultaneously contains N, C and Co. The tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine has a highly conjugated pi system and good chemical stability and thermal stability, and can be subjected to heat treatment to obtain a metal and nitrogen double-doped carbon material Co/N/C and show good oxygen reduction catalytic activity. The invention takes tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine as a cross-linking agent, which is beneficial to the precursor to form high-density Co-Nx active sites in the pyrolysis process. In addition, the constructed three-dimensional porous nano structure is also an effective means for improving the electrocatalytic performance; the disordered mesoporous structure not only can provide higher specific surface area and larger pore volume so as to expose more active sites, but also can be used as a way for transporting substances such as oxygen and the like to further improve the mass transfer rate of reactants to the catalyst. The embodiment results show that the oxygen reduction catalyst provided by the invention contains N, C and Co elements, has a rich pore structure, has a large number of mesoporous structures, has excellent electrochemical performance, and has high catalytic activity for oxygen reduction reaction.

Drawings

FIG. 1 is a plot of cyclic voltammetry measurements of each of the products of example 1 in a 0.1MKOH solution;

FIG. 2 shows the results of example 1 in O₂Linear sweep voltammetry test curves in saturated 0.1MKOH solution;

FIG. 3 is a plot of cyclic voltammetry measurements for each of the products of example 2 in a 0.1MKOH solution;

FIG. 4 shows the results of example 2 in O₂Linear Sweep Voltammetry (LSV) test curve in saturated 0.1MKOH solution;

FIG. 5 is an X-ray diffraction pattern of the Co/N/C-800 oxygen reduction catalyst of example 1;

FIG. 6 is a plot of cyclic voltammetry measurements for the Co/N/C-800 oxygen reduction catalyst of example 1 in 0.1MKOH solution;

FIG. 7 is a plot of the linear sweep voltammetry measurements of the Co/N/C-800 oxygen reduction catalyst of example 1 at different rotational speeds;

FIG. 8 is an SEM photograph of the Co/N/C-800 oxygen reduction catalyst of example 1;

FIG. 9 is N of Co/N/C-800 oxygen reduction catalyst of example 1₂Adsorption-desorption isotherms.

Detailed Description

The invention provides a method for preparing an oxygen reduction catalyst based on tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine aerogel, which comprises the following steps:

(1) mixing tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine, an organic solvent and an acetic acid-amino-rich organic matter mixed solution to obtain hydrogel;

(2) soaking the hydrogel obtained in the step (1) in water to remove redundant solvent, taking out the hydrogel, and then soaking the hydrogel in a graphene oxide solution or a multi-walled carbon nanotube solution for adsorption to obtain a composite hydrogel;

(3) freezing and drying the composite hydrogel obtained in the step (2) to obtain composite aerogel;

(4) and (4) carrying out high-heat treatment on the composite aerogel obtained in the step (3) under a protective atmosphere to obtain the oxygen reduction catalyst.

The preparation method comprises the step of mixing tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine, an organic solvent and an acetic acid-amino-rich organic matter mixed solution to obtain the hydrogel.

According to the invention, preferably, the tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine is added into an organic solvent, then ultrasonic dispersion is carried out to obtain a dispersion solution, and then the dispersion solution is mixed with the acetic acid-amino-rich organic matter mixed solution. This mixing sequence can make each material mix more even, and then guarantees the homogeneity of product. In the present invention, the organic solvent is preferably N, N-dimethylformamide, methanol, ethanol or acetone; the ratio of the mass of the tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine to the volume of the organic solvent is preferably (0.01-0.5) g, (1-5) mL, more preferably (0.03-0.25) g, (2-4) mL, and most preferably (0.06-0.12) g, (2-3) mL; the ultrasonic frequency of ultrasonic dispersion is 30-50 KHz, more preferably 40-45 KHz, and the time is preferably 5-10 min, more preferably 6-8 min.

The acetic acid-amino-rich organic matter mixed solution is a mixed aqueous solution of acetic acid and amino-rich organic matter, and the amino-rich organic matter is preferably chitosan and/or dopamine; the stereoregularity and intermolecular hydrogen bonds of the amino-rich organic molecules make it difficult to dissolve in most organic solvents, water and alkali, but the amino groups are present in dilute acid as H⁺Activity is sufficiently equal to-NH₂At a concentration of (2), make-NH₂Protonation to-NH³⁺The stereoregularity and hydrogen bonds among molecules are destroyed, and the-OH and water molecules are hydrated, so that the amino-rich organic molecules are expanded and dissolved. In the invention, the mass concentration of acetic acid in the acetic acid-amino-rich organic matter mixed solution is preferably 0.1-5%, more preferably 1-3%, and the mass concentration of amino-rich organic matter is preferably 1-5%, more preferably 2-3%; the volume of the organic solvent and the mass ratio of the acetic acid-amino-rich organic matter mixed liquid are preferably (1-3) ml and (2-10) g, and more preferably 2ml and (4-6) g.

In the invention, the tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine, the organic solvent and the acetic acid-amino-rich organic matter mixed solution are preferably mixed and then quickly vibrated, and the vibration is based on obtaining uniform dark green hydrogel without any specific requirement.

The cobalt tetra-beta- (4-aldehyde phenoxy) phthalocyanine is specifically used as a cross-linking agent, and amino-rich organic matters (such as chain-shaped chitosan) are mutually connected to form a three-dimensional network structure by the cross-linking agent.

The method comprises the steps of (1) soaking the hydrogel in water to remove redundant solvent, taking out the hydrogel, and then soaking the hydrogel in a graphene oxide solution or a multi-walled carbon nanotube solution for adsorption to obtain the composite hydrogel.

In the invention, the volume ratio of the organic solvent in the step (1) to the water in the step (2) is preferably (1-5): 250-350), more preferably (2-4): 280-320, and most preferably (2-3): 300-310. Since the hydrogel is a polymer with a three-dimensional network structure, which has hydrophilic groups, can be swelled by water but is insoluble in water, can absorb a large amount of water in water to be swelled significantly, and can continuously keep the original structure without being dissolved after being swelled significantly; the organic solvent used is miscible with water, so as to remove the organic solvent.

The time for soaking the hydrogel in water in the step (2) to remove the excessive solvent is preferably not less than 6 hours, more preferably 6-15 hours, and most preferably 10-12 hours. The invention preferably pumps away the solvent by means of suction filtration, and retains the block-shaped hydrogel. According to the invention, if a large amount of water is not used for removing the organic solvent in the hydrogel system, the organic solvent is likely to be incompletely volatilized during freeze drying and remain in the aerogel system, so that the formation of cavities is influenced, and the performance is poor.

The graphene oxide solution in the step (2) is preferably an aqueous solution of graphene oxide, and the concentration of the graphene oxide solution is preferably 1-10 mg/mL, more preferably 2-8 mg/mL, and most preferably 5-6 mg/mL; the multiwalled carbon nanotube solution is preferably a multiwalled carbon nanotube aqueous solution, and the concentration of the multiwalled carbon nanotube aqueous solution is preferably 1-10 mg/mL, more preferably 2-8 mg/mL, and most preferably 5-6 mg/mL; the volume ratio of the water to the graphene oxide solution or the multi-walled carbon nanotube solution in the step (2) is preferably (250-350): 5-15), more preferably (280-320): 8-12, and most preferably (300-310): 10-11); the adsorption time in the step (2) is preferably 1-10 h, more preferably 2-8 h, and most preferably 4-6 h.

The hydrogel is taken out and then soaked in the graphene oxide aqueous solution to mainly generate physical action, the graphene oxide or the multi-walled carbon nano tube has a plurality of oxygen-containing functional groups (such as-COOH and-OH) so as to show electronegativity in the aqueous solution, and amino-rich organic matters such as chitosan and positively charged-NH³⁺Therefore, graphene oxide or multi-walled carbon nanotubes can be combined into hydrogel through electrostatic interaction, and the composite hydrogel is obtained. The chemical composition of the dark green hydrogel obtained in the step (1) is as follows: tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine&The chitosan and the composite hydrogel comprise the following chemical components: tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine&Chitosan&Graphene oxide or tetra-beta- (4-aldehyde phenoxy) cobalt phthalocyanine&Chitosan&Dissolving the multi-wall carbon nano-tube.

The composite aerogel obtained in the step (2) is subjected to freeze drying to obtain the composite aerogel. The temperature of the freeze drying in the step (3) is preferably-60 to-50 ℃, more preferably-57 to-55 ℃, and the time is preferably 16 to 24 hours, more preferably 18 to 20 hours. The invention utilizes a freeze dryer to carry out freeze drying treatment on the composite hydrogel: firstly, freezing the composite hydrogel by using liquid nitrogen, and then removing the solvent by sublimation under a vacuum condition by using a freeze-drying technology to obtain the light green composite aerogel.

In a protective atmosphere, the composite aerogel obtained in the step (3) is subjected to high-heat treatment to obtain the oxygen reduction catalyst. The protective atmosphere in the step (4) is preferably an argon atmosphere or a nitrogen atmosphere; the temperature of the high-heat treatment is preferably 600-900 ℃, more preferably 700-850 ℃, and most preferably 750-800 ℃; the time is preferably 1 to 3 hours, and more preferably 2 hours. The temperature is preferably increased to the high heat treatment temperature at the speed of 2-4 ℃/min, and the heat is preserved at the temperature for high heat treatment, more preferably 3 ℃/min; after the high-heat treatment is finished, the temperature is preferably reduced to the room temperature in a natural cooling mode.

Under the protection of protective atmosphere, when the composite aerogel is subjected to high-temperature treatment, chemical bonds in molecules are broken, atoms are rearranged, and a graphitized carbon material is formed; meanwhile, metal atoms or other non-metal heteroatoms are also doped into the carbon material and become oxygen reduction catalytic active sites.

The invention also provides an oxygen reduction catalyst obtained by the method in the technical scheme, and the oxygen reduction catalyst simultaneously contains N, C and Co.

The technical solutions provided by the present invention are described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.