CN114715876A - Biomass tar-based dual-functional carbon-based electrocatalytic material and preparation method thereof - Google Patents

Abstract

The invention discloses a biomass tar-based dual-function carbon-based electrocatalysis material and a preparation method thereof, belonging to the technical field of secondary resource utilization. According to the method, biomass tar is used as a carbon source, melamine is used as a nitrogen source, oxygen-containing functional groups are constructed on the surface of a pyrolyzed biomass tar-based carbon material through acid oxidation, and nitrogen heteroatoms are doped on the surface of the carbon material by utilizing an organic synthesis reaction mechanism. The preparation method comprises the following steps: (1) uniformly dispersing and mixing the biomass tar and the pore-forming agent; (2) pyrolyzing the mixture of step (1) in a tubular furnace; (3) taking out the product in the step (2), grinding, and oxidizing in a mixed acid solution; (4) and (4) mixing the carbon material in the step (3) with a nitrogen source. When the obtained product is used for energy conversion, the obtained product has high-efficiency bifunctional catalytic activity and excellent cycle stability. The invention solves the problems of high cost, poor circulation stability and the like of the bifunctional catalyst, realizes high-value utilization of biomass tar and has wide prospect.

Description

A kind of biomass tar-based bifunctional carbon-based electrocatalytic material and preparation method thereof

technical field

The invention belongs to the technical field of energy conversion, and discloses a biomass tar-based bifunctional carbon-based electrocatalytic material and a preparation method thereof.

Background technique

With the continuous growth of global energy demand, the development of energy storage technology is imperative. Among them, electrochemical energy storage has received extensive attention and applications due to its high energy density, long service life, and low self-discharge. However, slow oxygen reduction (ORR) kinetics greatly limit the development of energy conversion technologies. Platinum (Pt)-based catalysts exhibit excellent performance and are crucial for enhancing cathodic ORR. However, platinum's high cost, scarcity, and poor methanol resistance make it difficult to achieve widespread applications in the field of energy conversion. Noble metal alloys, single-atom, core-shell structures, and nano-confined structures have been developed to reduce the amount of noble metals, but achieving large-scale precise synthesis of nano-micro structures remains a huge challenge. Transition metals have attracted extensive attention as promising alternatives to noble metal catalysts due to their good stability. In particular, recently developed single-atom catalysts (SACs) with individual Fe or Co single-atom sites, supported by N-doped carbon, have emerged as the most promising due to their excellent ORR electrocatalytic performance and maximized atom utilization one of the alternatives. However, the problems of leaching and agglomeration of transition metals during use still need to be solved urgently. Therefore, it is of great significance to explore metal-free catalysts to replace metal catalysts.

Carbon materials have the advantages of wide sources, easy regulation, and good stability, so they have received extensive attention. However, due to the uniform charge distribution of carbon materials, their intrinsic catalytic activity is not high. Introducing heteroatom (nitrogen, sulfur, boron, phosphorus, etc.) doping into carbon materials can effectively improve the electronic properties and chemical reactivity of carbon-based materials, thereby significantly improving the electrochemical properties of the materials. Based on the difference in electronegativity between heteroatoms and carbon atoms, the heteroatom-doped carbon interface atomic domain with modified electronic structure has the characteristics of large charge polarization and minimal change in conjugation length, so the atomic domain can be Delivers high electrochemical activity. At the same time, lone pairs of electrons on some heteroatoms (such as N and S) act as carriers to promote electron transfer, which can change the spatial structure of the π system of carbon materials, thereby changing the van der Waals force of the carbon layer, which is beneficial to control the adsorption capacity of the material to the precursor. . Generally speaking, carbon materials doped with foreign atoms/groups have high surface activity and can be used as electrode materials in electrochemical reactions, significantly improving the catalytic performance of the materials. Among them, nitrogen atom has an atomic size similar to carbon and greater electronegativity, which is the mainstream direction of heteroatom doping of carbon-based catalytic materials. At present, most of the heteroatom-doped carbon material substrates are carbon nanotubes, graphene, covalent organic frameworks (COFs), etc. These materials have excellent electrical conductivity, which helps to enhance electron transfer between the interface and the current collector. The preparation methods of these advanced carbon-based materials usually have long processes, harsh operating conditions, and complex precursors in the preparation process. Biomass tar is a by-product of biomass gasification process, which is cheap and easy to obtain, and its main component is benzene derivatives. At high temperature, biomass tar has the characteristics of a mobile phase, and benzene derivatives are prone to cross-linking reaction to generate fused-ring carbon, thereby forming a carbon substrate with a high degree of order. A high degree of ordering is an important guarantee for the excellent electrical conductivity of carbon-based catalytic materials. At the same time, biomass tar itself contains a small amount of heteroatoms such as N and S. Through modulation, the content of aromatic ring heteroatoms (N, S, O) is increased, and the self-doping molecular structure is easily formed during the pyrolysis process. It is beneficial to increase the polarization of carbon charges, thereby realizing the improvement of electrocatalytic activity. Therefore, biomass tar is an excellent raw material for carbon-based catalysts. The invention provides a biomass tar-based bifunctional carbon-based electrocatalytic material and a preparation method thereof. The preparation method is simple, green, and easy to prepare on a large scale. The invention realizes the high-value utilization of cheap biomass tar and is helpful for In order to promote the "carbon neutralization" process, the prepared high-efficiency bifunctional carbon-based catalytic materials can be widely used in various energy conversion fields such as all-water electrolysis, fuel cells, and metal-air batteries.

SUMMARY OF THE INVENTION

In order to solve the following two problems: (1) carbon-based electrocatalytic materials have a long preparation process, harsh operating conditions, and require complex precursors; (2) high-value utilization of waste biomass tar. The invention provides a biomass tar-based bifunctional carbon-based electrocatalytic material and a preparation method thereof, comprising the following steps:

(1) uniformly disperse and mix biomass tar and pore-forming agent;

(2) the mixture of step (1) is pyrolyzed;

(3) after taking out step (2) product grinding, oxidize in mixed acid solution;

(4) Mixing the carbon material in step (3) with a nitrogen source, and forming heteroatom doping on its surface by pyrolysis.

Further, the pore-forming agent in step (1) is one or more of the following combinations: potassium hydroxide, ammonium carbonate, ammonium bicarbonate, ammonium chloride;

Further, the mass ratio of the biomass tar to the pore-forming agent in step (1) is between 1:1 and 1:5, and the optimized mass ratio is between 1:3 and 1:5.

Further, the solvent in step (1) is one or more of the following combinations, deionized water, ethanol, ethylene glycol, methanol, glycerol, isopropanol, n-butanol;

Further, the pyrolysis temperature in step (2) is 700°C to 1200°C, and the pyrolysis atmosphere is one or any combination of the following gases: argon, nitrogen, carbon dioxide, water vapor, and ammonia;

Further, the mixed acid in step (3) is one of the following solutions or a combination of any two or more thereof: nitric acid, sulfuric acid, hypochlorous acid, hydrogen peroxide;

Further, the oxidation time in step (3) is 24～96h, and the oxidation time after optimization is 36～48h;

Further, the pyrolysis temperature in step (4) is 400°C to 900°C, and the pyrolysis atmosphere is one or any combination of the following gases: argon, nitrogen, and ammonia.

The beneficial effects of the invention are as follows: on the one hand, biomass tar is used as raw material to prepare carbon-based catalyst, the process is green and low-cost, and the mobile phase characteristics of biomass tar at high temperature are conducive to the improvement of the degree of graphitization, which overcomes advanced carbon-based catalysts. The material preparation process is long, the operating conditions are harsh, and complex precursors are required; on the other hand, the organic synthesis reaction is used to directionally introduce heteroatoms at the interface of the carbon material, which significantly improves the electrochemical activity of the catalytic material; it is an efficient bifunctional carbon-based catalyst. The preparation and application of it provides a broad prospect.

Description of drawings

Fig. 1 is the concrete flow chart of the present invention

FIG. 2 is a SEM picture of the carbon material after pyrolysis provided by the specific embodiment 1 of the present invention.

FIG. 3 is a BET picture of the carbon material after pyrolysis provided by the specific embodiment 1 of the present invention.

FIG. 4 is the XPS peak split result of carbon after interface modification provided by specific embodiment 1 of the present invention.

FIG. 5 is the FT-IR result after the interface oxidation provided by the specific embodiment 1 of the present invention.

FIG. 6 is a bifunctional electrochemical activity diagram provided by the specific embodiment 1 of the present invention.

FIG. 7 is the bifunctional electrochemical kinetic performance of the carbon material provided by the specific embodiment 1 of the present invention.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments.

The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials can be obtained from commercial sources unless otherwise specified.

Example 1

Biomass tar and pore-forming agent were dispersed in a solution of ethanol/deionized water (1:1) according to the mass ratio of 2:1, and stirred on a magnetic stirrer for 2 hours to form mixed solution A; then solution A was poured into corundum In the crucible, the temperature was raised to 800°C under an argon atmosphere, and the temperature was kept constant for 2 hours, and then the powder B was taken out and ground into powder B; then powder B was added to 30 mL of a mixed solution of 30 wt% nitric acid and hydrogen peroxide (1:1), stirred for 24 hours, and washed with water to medium The powder C was obtained by drying in a stable manner; the powder C was ground and mixed with melamine (mass ratio 5:1), and then heated to 500 °C at a rate of 5 °C/min under an argon atmosphere, and kept at a constant temperature for 3 h. Finally, a carbon-based bifunctional electrocatalytic material was obtained. The material has a rich mesoporous structure and surface functional groups. It has also been proved that nitrogen heteroatoms are incorporated into the carbon interface to form nitrogen-containing carbon rings. (OER) reaction exhibits excellent bifunctional catalytic activity.

Scanning electron microscope (JSM-7800) was used to test the microscopic morphology of carbon-based catalytic materials under the above conditions. The test results are shown in Figure 1 respectively. The pore structure of the material is shown in Figure 2, showing a uniform mesoporous structure. XPS was used to characterize the incorporated form of N, as shown in Figure 3. The FT-IR results are shown in Fig. 4, and the carbonyl and aldehyde functional groups on the surface of powder C were significantly increased after oxidation in mixed acid.

The carbon-based bifunctional catalytic material prepared in Example 1 was coated on the glassy carbon electrode of the rotating ring disk to carry out the ORR/OER bifunctional electrocatalytic reaction. /AgCl was used as the reference electrode. Before the test, oxygen was injected into the electrolyte for 10 min to achieve oxygen saturation in the electrolyte. The electrochemical workstation is CHI760e, the scanning speed of LSV is 50mV/s, and the rotational speed is 400, 625, 900, 1225, 1600, and 2500 rpm, respectively. The electrochemical reactivity is shown in Fig. 4, and the kinetic activity is shown in Fig. 5.

Example 2

The biomass tar and the pore-forming agent were dispersed in deionized water according to the mass ratio of 4:1, and stirred on a magnetic stirrer for 2 h to form a mixed solution A1; then the solution A1 was poured into a corundum crucible, and the temperature was raised to 100 °C under an argon atmosphere. 800 ° C, constant temperature for 2 hours, take out and grind into powder B1; then add powder B1 to 30 mL of a mixed solution of 30% wt% nitric acid and hydrogen peroxide (1:1), stir for 24 hours, wash with water until neutral and dry to obtain powder C1; Powder C1 and melamine were ground and mixed (mass ratio 4:1) and then heated to 500°C at a rate of 5°C/min in an argon atmosphere, and kept at a constant temperature for 3 hours. Finally, carbon-based bifunctional electrocatalytic materials are obtained.

Example 3

The biomass tar and the pore-forming agent were dispersed in a solution of ethanol/deionized water (1:1) according to the mass ratio of 5:1, and stirred on a magnetic stirrer for 4 hours to form a mixed solution A2; then the solution A2 was poured into corundum In the crucible, the temperature was raised to 1000°C under an argon atmosphere, the temperature was kept constant for 2 hours, and then the powder B2 was taken out and ground into powder B2; then powder B2 was added to 30 mL of a mixed solution of 30% wt% nitric acid and hydrogen peroxide (1:1), stirred for 48 hours, and washed with water. Dry to neutrality to obtain powder C2; grind and mix powder C2 and melamine (mass ratio 5:1), and then raise the temperature to 500°C at a rate of 5°C/min under an argon atmosphere, and maintain a constant temperature for 3 hours. Finally, carbon-based bifunctional electrocatalytic materials are obtained.

Example 4

The biomass tar and pore-forming agent were dispersed in a solution of ethanol/deionized water (1:1) according to the mass ratio of 5:1, and stirred on a magnetic stirrer for 2 hours to form a mixed solution A3; then the solution A3 was poured into graphite In the crucible, the temperature was raised to 800°C in an ammonia gas atmosphere, and the temperature was kept constant for 2 hours, and then the powder B3 was taken out and ground into powder B3; then, the powder B3 was added to 30 mL of a 30% wt% nitric acid solution, stirred for 72 hours, washed with water until neutral, and dried to obtain powder C3; After grinding and mixing powder C3 and melamine (mass ratio 5:1), the temperature was raised to 500°C at a rate of 5°C/min under an argon atmosphere, and the temperature was kept constant for 3 hours. Finally, carbon-based bifunctional electrocatalytic materials are obtained.

Example 5

The biomass tar and pore-forming agent were dispersed in a solution of ethanol/deionized water (1:1) according to the mass ratio of 5:1, and stirred on a magnetic stirrer for 4 hours to form a mixed solution A4; then the solution A4 was poured into corundum In the crucible, the temperature was raised to 900°C under an argon atmosphere, and the temperature was kept constant for 2 hours, and then the powder B4 was taken out and ground into powder B4; then powder B4 was added to 30 mL of a mixed solution of 30% wt% nitric acid and hydrogen peroxide (1:1), stirred for 24 hours, and washed with water. Dry to neutrality to obtain powder C4; grind and mix powder C4 and melamine (mass ratio 5:1), and then raise the temperature to 700°C at a rate of 5°C/min under an argon atmosphere, and maintain a constant temperature for 3 hours. Finally, carbon-based bifunctional electrocatalytic materials are obtained.

Example 6

The biomass tar and the pore-forming agent were dispersed in ethanol according to the mass ratio of 5:1, and stirred on a magnetic stirrer for 3 hours to form a mixed solution A5; then the solution A5 was poured into a corundum crucible and heated to 800 ° C under a nitrogen atmosphere. , after constant temperature for 1 h, take out and grind into powder B5; then add powder B5 to 30 mL of a mixed solution of 30% wt% hydrogen peroxide (1:1), stir for 48 h, wash with water until neutral and dry to obtain powder C5; powder C5 and melamine After grinding and mixing (mass ratio 5:1), the temperature was raised to 500 °C at a rate of 5 °C/min under an argon atmosphere, and the temperature was kept constant for 3 h. Finally, carbon-based bifunctional electrocatalytic materials are obtained.

Example 7

The biomass tar and pore-forming agent were dispersed in a solution of ethanol/deionized water (1:1) according to the mass ratio of 5:1, and stirred on a magnetic stirrer for 4 hours to form a mixed solution A6; then the solution A6 was poured into graphite In the crucible, the temperature was raised to 1200°C under an argon atmosphere, and the temperature was kept constant for 2 hours, and then the powder B6 was taken out and ground into powder B6; then powder B6 was added to 30 mL of a mixed solution of 30% wt% nitric acid and hydrogen peroxide (1:1), stirred for 72 hours, and washed with water. Dry to neutrality to obtain powder C6; grind and mix powder C6 and melamine (mass ratio 4:1), and then raise the temperature to 900°C at a rate of 5°C/min under an argon atmosphere, and maintain a constant temperature for 3 hours. Finally, carbon-based bifunctional electrocatalytic materials are obtained.

Example 8

The biomass tar and the pore-forming agent were dispersed in a solution of ethanol/deionized water (1:1) according to the mass ratio of 5:1, and stirred on a magnetic stirrer for 2 hours to form a mixed solution A7; then the solution A7 was poured into corundum In the crucible, the temperature was raised to 1200°C under an argon atmosphere, and the temperature was kept constant for 2 hours, and then the powder B7 was taken out and ground into powder B7; then powder B7 was added to 30 mL of a mixed solution of 30 wt% nitric acid and hydrogen peroxide (2:1), stirred for 36 hours, and washed with water to medium The powder C7 was obtained by dry drying; the powder C7 was ground and mixed with melamine (mass ratio 3:1), and then heated to 900 °C at a rate of 5 °C/min under a nitrogen atmosphere, and kept at a constant temperature for 2 h. Finally, carbon-based bifunctional electrocatalytic materials are obtained.

In the description of this specification, reference is made to the description of the terms "one embodiment", "some embodiments", "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. It is intended that a particular feature, structure, material or characteristic described in connection with this embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The above content is a further detailed description of the present invention in conjunction with specific embodiments, and it cannot be considered that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art to which the present invention pertains, some simple deductions or substitutions can be made without departing from the concept of the present invention.

Claims (9)

1. a high-efficiency bifunctional water-splitting carbon-based catalytic material and preparation method thereof, is characterized in that, comprises the following steps: (1) uniformly disperse and mix biomass tar and pore-forming agent; (2) the mixture of step (1) is pyrolyzed; (3) after taking out step (2) product grinding, oxidize in mixed acid solution; (4) Mixing the carbon material in step (3) with a nitrogen source, and forming heteroatom doping on its surface by pyrolysis. 2. a kind of biomass tar-based bifunctional carbon-based electrocatalytic material and preparation method thereof as claimed in claim 1, it is characterized in that: the biomass tar used in described step (1) is that biomass gasification process produces The by-products of which are the main components of benzene derivatives; 3. a kind of biomass tar-based bifunctional carbon-based electrocatalytic material and preparation method thereof as claimed in claim 1, is characterized in that: the pore-forming agent in described step (1) is following one or more Combination: potassium hydroxide, ammonium carbonate, ammonium bicarbonate, ammonium chloride; 4. a kind of biomass tar-based bifunctional carbon-based electrocatalytic material and preparation method thereof as claimed in claim 1, it is characterized in that: the mass ratio of biomass tar in described step (1) and pore-forming agent is in Between 1:1 and 1:5, the optimized mass ratio is between 1:3 and 1:5. 5. a kind of biomass tar-based bifunctional carbon-based electrocatalytic material and preparation method thereof as claimed in claim 1, is characterized in that: the solvent in described step (1) is following one or more combination , deionized water, ethanol, ethylene glycol, methanol, glycerol, isopropanol, n-butanol; 6. A biomass tar-based bifunctional carbon-based electrocatalytic material and a preparation method thereof as claimed in claim 1, wherein the pyrolysis temperature in the step (2) is 700°C to 1200°C, and the thermal The solution atmosphere is one or any combination of the following gases: argon, nitrogen, carbon dioxide, water vapor, ammonia; 7. a kind of biomass tar-based bifunctional carbon-based electrocatalytic material and preparation method thereof as claimed in claim 1, is characterized in that: the mixed acid in described step (3) is one of following solutions or wherein any two One or more kinds of combination: nitric acid, sulfuric acid, hypochlorous acid, hydrogen peroxide. 8. A kind of biomass tar-based bifunctional carbon-based electrocatalytic material and preparation method thereof as claimed in claim 1, characterized in that: the oxidation time in the step (3) is 24-96 h, and the optimized oxidation time is For 36 ~ 48h. 9 . The biomass tar-based bifunctional carbon-based electrocatalytic material according to claim 1 and a preparation method thereof, wherein the pyrolysis temperature in the step (4) is 400° C. to 900° C., and the thermal The solution atmosphere is one or any combination of the following gases: argon, nitrogen, and ammonia.

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