阅读说明：本技术 一种基于白千层树皮粉的非贵金属电催化剂及其制备方法和应用 (Non-noble metal electrocatalyst based on cajeput bark powder and preparation method and application thereof ) 是由 陈德良 杨华明 李铭 李涛 杨震宇 孙成华 崔立峰 李超 林晓莹 于 2019-07-11 设计创作，主要内容包括：本发明涉及一种基于白千层树皮粉的非贵金属电催化剂及其制备方法和应用。该制备方法包括如下步骤：S1：将咪唑类配体材料、硼源、三聚氰胺、白千层树皮粉和钴盐混合于溶剂中得悬浮液,超声,干燥得产物；S2：将产物和造孔剂混合,碳化得碳化产物；S3：将碳化产物酸洗后干燥即得所述非贵金属电催化剂。本发明提供的制备方法具有工艺流程简单、原料成本低廉、便于宏量制备而适合于工业生产等优点；制备得到的非贵金属电催化剂具有与商业Pt/C催化剂相近的,甚至比商业Pt/C催化剂更高、更稳定的电催化氧还原(ORR)性能,可望应用于大型锌空气电池、铝空气电池以及燃料电池的新能源装置。(The invention relates to a non-noble metal electrocatalyst based on cajeput bark powder and a preparation method and application thereof. The preparation method comprises the following steps: s1: mixing imidazole ligand material, boron source, melamine, cajeput bark powder and cobalt salt in a solvent to obtain a suspension, and performing ultrasonic treatment and drying to obtain a product; s2: mixing the product with a pore-forming agent, and carbonizing to obtain a carbonized product; s3: and (4) washing the carbonized product with acid and drying to obtain the non-noble metal electrocatalyst. The preparation method provided by the invention has the advantages of simple process flow, low raw material cost, convenience for macro-preparation, suitability for industrial production and the like; the prepared non-noble metal electrocatalyst has electrocatalytic oxygen reduction (ORR) performance similar to that of a commercial Pt/C catalyst, even higher and more stable than that of the commercial Pt/C catalyst, and is expected to be applied to new energy devices of large-scale zinc-air batteries, aluminum-air batteries and fuel cells.)

1. A preparation method of a non-noble metal electrocatalyst based on cajeput bark powder is characterized by comprising the following steps:

s1: mixing imidazole ligand material, boron source, melamine, cajeput bark powder and cobalt salt in a solvent to obtain a suspension, and performing ultrasonic treatment and drying to obtain a product; the mass ratio of the cobalt salt to the cajeput bark powder is 20-50: 100, and the mass ratio of the MOF ligand material to the cajeput bark powder is 50-80: 100; the mass ratio of the boron source to the cajeput bark powder is 30-50: 100, and the mass ratio of the melamine to the cajeput bark powder is 60-100: 100;

s2: mixing the product with a pore-forming agent, and carbonizing at 600-1100 ℃ in an inert atmosphere to obtain a carbonized product;

s3: and (4) washing the carbonized product with acid and drying to obtain the non-noble metal electrocatalyst.

2. The preparation method according to claim 1, wherein the boron source in S1 is one or more of boric acid, boric acid or pyroboric acid; the imidazole ligand material in S1 is one or more of 2-methylimidazole, N-methylimidazole, 4-methylimidazole or 1, 2-dimethylimidazole; the cobalt salt in S1 is one or more of cobalt nitrate, cobalt sulfate, cobalt chloride, cobalt acetate, cobalt hydroxide or cobalt acetylacetonate.

3. The method according to claim 1, wherein the pore-forming agent in S2 is NaCl, KCl, LiCl, ZnCl₂One or more of KOH or NaOH; and S2, the mass ratio of the product to the pore-forming agent is 1: 2-6.

4. The method according to claim 1, wherein the mixing in S2 and S3 is independently selected from one or more of grinding, sanding, ball milling or stirring; the mixing time is independently selected from 5 to 600 minutes.

5. The preparation method of claim 1, wherein the inert atmosphere in S2 is one or more of argon and nitrogen.

6. The method according to claim 1, wherein the acid washing in S3 comprises: and stirring the carbonized product in an acid solution for reaction for 0.1-24 hours, washing off excessive acid, and drying.

7. The preparation method of claim 1, wherein the step of drying in S3 and calcining at 600-1100 ℃ in an inert atmosphere to obtain the non-noble metal electrocatalyst is further included.

8. The preparation method according to claim 7, wherein the inert atmosphere in S3 is one or more of argon or nitrogen; the calcining time in S3 is 0.5-12 hours; the temperature rise rate is 1-50 ℃/min.

9. A non-noble metal electrocatalyst based on cajeput bark powder, characterized in that it is prepared by the preparation method of any one of claims 1 to 8.

10. Use of the cajeput bark powder based non-noble metal electrocatalyst according to claim 9 for the preparation of new energy devices.

Technical Field

The invention relates to the field of inorganic nano materials and electrochemical catalysis, in particular to a non-noble metal electrocatalyst based on cajeput bark powder and a preparation method and application thereof.

Background

The Oxygen Reduction Reaction (ORR) plays a key role in fuel cells. Because the oxygen reduction reaction has a complex process and a high reaction energy barrier, a high-performance electrocatalyst is required to promote the reaction to proceed smoothly. Pt-based catalysts are considered to be the most efficient oxygen reduction electrocatalysts; however, metal Pt is expensive, the earth resource reserves are small, and the requirement of large-scale application cannot be met, and development of a catalyst which is cheap, convenient to obtain and easy to prepare to replace a Pt-based catalytic material is urgently needed. Against this background, international material scientists have developed various methods to prepare non-platinum catalysts, such as non-noble metal catalyst systems like carbon supported metal macrocycles (ACS Energy lett.2018,3,252), metal oxides (angelw. chem. int.ed.2016,55,4087), metal chalcogenides (adv. funct. mater.2017, 27,1702300), metal carbides (j.am. chem. soc.2017,139,453), metal nitrides (biosens. bioelectrron.2016, 83,68), carbon supported alloys (electrotechnim. acta.2016,220, 354). Because the performance requirements on the catalyst in the practical application scene of the fuel cell are very strict, the price is required to be low, and the currently developed non-platinum-based oxygen reduction catalysts cannot meet the requirements of commercial application, and the research and development of novel, efficient and cheap electrocatalysts are still urgent and are challenging.

In the cheap and abundant non-noble metal catalyst, the biomass porous carbon catalyst in which transition metal elements (Fe, Co, Ni, Mn and the like) and non-metal elements such as nitrogen, boron and the like are codoped shows excellent comprehensive performance. The biomass-based porous carbon material is renewable, wide in material source, low in price and green and ecological. Heretofore, Fe-N-C catalysts have optimum ORR catalytic activity under acidic conditions, but since iron readily dissolves under acidic conditions to form iron ions, H, a by-product of the reaction with ORR₂O₂Fenton's reagent (Fenton) with strong oxidizing property is formed, the proton exchange membrane is seriously damaged, short circuit is caused, and the failure is caused, so that a new material system must be developed. At present, a Co-N-C system becomes an international research hotspot, and partial research results show that the reaction rate is obviously accelerated and the output power of the fuel cell is improved when the Co-N-C catalyst is applied to the ORR process of the fuel cell (adv. Mater.2019, 1805126).

Therefore, the development of a novel Co-N-C catalyst which is cheap, abundant, high in ORR catalytic activity and good in stability has important research significance and application value.

Disclosure of Invention

The invention aims to solve the problems that the existing platinum/carbon ORR electrocatalyst is expensive and small in resource amount, and an iron-nitrogen-carbon-based ORR electrocatalyst is unstable, and provides a preparation method of a non-noble metal electrocatalyst based on cajeput bark powder. The non-noble metal electrocatalyst provided by the invention takes the biomass charcoal of cajeput bark with a layered structure as a carrier, and the carrier has the advantages of a hierarchical pore structure, high specific surface area and the like, and provides rich embedded pore passages for doping atoms such as Co, N, B and the like; the bark of the cajeput is wide in source, renewable and low in price; b, N, Co cluster structure is loaded on the carrier, and the synergy of B, N, Co and other multi-element codoping is beneficial to improving the catalytic performance and improving the catalytic performance. The non-noble metal electrocatalyst provided by the invention has electrocatalytic oxygen reduction (ORR) performance similar to that of a commercial Pt/C catalyst, even higher and more stable than that of the commercial Pt/C catalyst, has excellent oxygen reduction catalytic activity, and is expected to be applied to new energy devices of large-scale zinc-air batteries, aluminum-air batteries and fuel cells. The preparation method provided by the invention has the advantages of simple process flow, low raw material cost, convenience for macro-preparation and suitability for industrial production.

Another object of the present invention is to provide a non-noble metal electrocatalyst based on bark powder of cajeput.

The invention also aims to provide application of the non-noble metal electrocatalyst based on the bark powder of cajeput to preparing fuel cells.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of a non-noble metal electrocatalyst based on cajeput bark powder comprises the following steps:

s1: mixing imidazole ligand material, boron source, melamine, cajeput bark powder and cobalt salt in a solvent to obtain a suspension, and performing ultrasonic treatment and drying to obtain a product; the mass ratio of the cobalt salt to the cajeput bark powder is 20-50: 100, and the mass ratio of the MOF ligand material to the cajeput bark powder is 50-80: 100; the mass ratio of the boron source to the cajeput bark powder is 30-50: 100, and the mass ratio of the melamine to the cajeput bark powder is 60-100: 100;

s2: mixing the product with a pore-forming agent, and carbonizing at 600-1100 ℃ in an inert atmosphere to obtain a carbonized product;

s3: and (4) washing the carbonized product with acid and drying to obtain the non-noble metal electrocatalyst.

Melaleuca leucadendra L, a tree belonging to the genus Melaleuca and the family Myrtaceae. The bark is grey white and is peeled off in a lamellar way; the soil is fond of warm and humid environment with sufficient sunlight, can resist drought and high temperature, can resist light frost and low temperature, has strong adaptability, and can be widely planted in Guangdong, Taiwan, Fujian, Guangxi and the like in China.

Researches show that the bark of cajeput is in a thin-layer structure, has the advantages of a hierarchical pore structure, high specific surface area and the like, provides rich embedded pore passages for doping atoms such as Co, N, B and the like, and is an ideal raw material for preparing the carbon nano material with high specific surface area and low vitamin; in addition, bark of cajeput can be continuously peeled off, a large amount of bark can be obtained without damaging trees, and the cost is low. B. N, Co, etc. is favorable to raising catalytic performance and raising its catalytic performance.

In addition, the imidazole ligand material and cobalt ions can form a cobalt-imidazole complex, so that better dispersion of Co element can be realized; the boron source and melamine can form melamine borate, in addition to providing the B element and N element, respectively.

According to the method, cajeput bark biomass charcoal is used as a carrier, blocky melamine borate is coated on the surface of the cajeput bark biomass charcoal, and the cajeput-imidazole complex is mixed in the blocky melamine borate, so that the cobalt element can be effectively dispersed by the method. Meanwhile, compared with melamine and boron sources, the melamine borate has certain thermal stability (commonly used as a flame retardant), can inhibit volatilization of nitrogen and boron elements in the carbonization process, and improves the doping efficiency of the nitrogen and boron elements. And mixing the S1, mixing the treated product with a pore-forming agent, and calcining to obtain the flaky porous doped carbon material with wrinkled surface. After acid cleaning, the generated metallic cobalt and pore-forming agent impurities can be removed, and the doped carbon material with a hierarchical pore structure (micropore and mesopore) can be obtained, and the specific surface area is large.

In the preparation method provided by the invention, the main raw material cajeput bark is renewable biomass waste, and other auxiliary reagents are low in price. The obtained porous carbon-doped electrocatalyst has catalytic performance similar to that of commercial Pt/C catalyst.

Namely, the non-noble metal electrocatalyst based on the cajeput bark powder provided by the invention has excellent oxygen reduction catalytic activity, and is expected to be applied to new energy devices of large zinc-air batteries, aluminum-air batteries and fuel cells.

The preparation method provided by the invention has the advantages of simple process flow, low raw material cost, convenience for macro-preparation, suitability for industrial production and the like.

Preferably, the mixing process in S1 is: adding imidazole ligand material, boron source and melamine into a solvent, and performing ultrasonic treatment; adding bark powder of Melaleuca Alternifolia L.and mixing, adding cobalt salt, and stirring to obtain suspension.

Sources of boron, imidazole-based ligand materials (e.g., alkyl imidazoles), and cobalt salts that are conventional in the art may be used in the present invention.

Preferably, the boron source in S1 is one or more of boric acid, metaboric acid, or pyroboric acid.

Preferably, the imidazole ligand material in S1 is one or more of 2-methylimidazole, N-methylimidazole, 4-methylimidazole or 1, 2-dimethylimidazole.

Preferably, the cobalt salt in S1 is one or more of cobalt nitrate, cobalt sulfate, cobalt chloride, cobalt acetate, cobalt hydroxide, or cobalt acetylacetonate.

Preferably, the particle size of the cajeput bark powder in S1 is not more than 50 mesh.

Preferably, the solvent in S1 is one or more of methanol, ethanol, isopropanol, or water.

Pore formers conventional in the art may be used in the present invention in conventional amounts.

Preferably, the pore-forming agent in S2 is NaCl, KCl, LiCl or ZnCl₂One or more of KOH or NaOH.

Preferably, the mass ratio of the product S2 to the pore-forming agent is 1: 2-6.

Preferably, the carbonization time in S2 is 0.5-12 h.

Preferably, the temperature rise rate in S2 is 1-50 ℃/min.

Preferably, the mixing mode in S2 is one or more of grinding, sanding, ball milling or stirring; the mixing time is 5-600 minutes.

Preferably, the inert atmosphere in S2 is one or more of argon or nitrogen.

Preferably, the pickling process in S3 is: and stirring the carbonized product in an acid solution for reaction for 0.1-24 hours, washing off excessive acid, and drying.

More preferably, the acidic solution is HCl solution or HNO₃Solutions or H₂SO₄One or more of the solutions.

More preferably, the concentration of the acidic solution is 0.1-5 mol/L.

Preferably, the mixing mode in S3 is one or more of grinding, sanding, ball milling or stirring; the mixing time is 5-600 minutes.

Preferably, the step of drying in S3 and then calcining in an inert atmosphere at 600-1100 ℃ to obtain the non-noble metal electrocatalyst.

The secondary calcination can improve the graphitization degree, increase the number of micropores, improve the conductivity of the catalyst and the transport capacity of current carriers, and further improve the catalytic activity of oxygen reduction.

The non-noble metal electrocatalyst obtained after secondary calcination has the advantages of high specific surface area, high catalytic activity and high stability, and has higher and more stable electrocatalytic oxygen reduction (ORR) performance than a commercial Pt/C catalyst: the half-wave potential of the catalyst is up to 0.831V (vs. RHE), which is better than that of a commercial 20% Pt/C catalyst (0.825V vs. RHE); the current density is superior to or close to that of a commercial 20% Pt/C catalyst; after 5000 cycles of test, the performance is not obviously reduced and is better than that of a commercial 20 percent Pt/C catalyst; methanol is stable against toxicity and is superior to commercial 20% Pt/C catalyst.

More preferably, the inert atmosphere in S3 is one or more of argon or nitrogen.

More preferably, the calcining time in S3 is 0.5-12 hours; the temperature rise rate is 1-50 ℃/min.

A non-noble metal electrocatalyst based on cajeput bark powder is prepared by the preparation method.

The application of the non-noble metal electrocatalyst based on the cajeput bark powder in preparing a new energy device is also within the protection scope of the invention.

Preferably, the new energy device is a zinc-air battery, an aluminum-air battery or a fuel cell.

Compared with the prior art, the invention has the following beneficial effects:

in the preparation method provided by the invention, the main raw material cajeput bark is renewable biomass waste, and other auxiliary reagents are low in price. The obtained non-noble metal electrocatalyst has similar to or even higher and more stable electrocatalytic oxygen reduction (ORR) performance than commercial Pt/C catalysts, and is expected to be applied to new energy devices of large-scale zinc-air batteries, aluminum-air batteries and fuel cells.

The preparation method provided by the invention has the advantages of simple process flow, low raw material cost, convenience for macro-preparation, suitability for industrial production and the like.

Drawings

FIG. 1 is a schematic diagram of the method of example 1 for preparing a non-noble metal electrocatalyst based on bark powder of Melaleuca alternifolia;

FIG. 2 is an infrared spectrum of the precursor of example 1;

FIG. 3 is an XRD contrast of the sample obtained in example 1 after calcination and after acid washing;

FIG. 4 is a scanning electron micrograph of bark powder of Melaleuca alternifolia;

FIG. 5 is a scanning electron micrograph of the precursor of example 1;

FIG. 6 is a scanning electron micrograph of a sample obtained after calcination of example 1;

FIG. 7 is a scanning electron micrograph of a sample obtained after acid washing in example 1;

FIG. 8 is a scanning electron micrograph of a sample obtained after the secondary calcination of example 1;

FIG. 9 shows the N values corresponding to the samples obtained after the primary and secondary calcinations in example 1₂Adsorption-desorption isotherms;

FIG. 10 is a graph of the pore size distribution of the samples of example 1 after the primary and secondary calcinations;

FIG. 11 is an XPS spectrum of samples of example 1 after primary and secondary calcinations;

FIG. 12 is a Co2p fine XPS spectrum of the sample after the second calcination of example 1;

FIG. 13 is a C1s fine XPS spectrum of the sample after the second calcination of example 1;

FIG. 14 is a B1s fine XPS spectrum of the sample after the second calcination of example 1;

FIG. 15 is a N1s fine XPS spectrum of a sample after a second calcination of example 1;

FIG. 16 is an LSV curve at 1600rpm for the samples of examples 1-3 after one calcination and a commercial platinum-carbon 20% Pt/C catalyst;

FIG. 17 is an LSV curve at 1600rpm for the samples of examples 1-3 after the secondary calcination and a commercial 20% Pt/C catalyst;

FIG. 18 is an LSV curve at 1600rpm for the porous biochar catalyst and the commercial 20% Pt/C catalyst provided in comparative example 1, comparative example 2;

FIG. 19 is a LSV curve of the non-noble metal electrocatalyst provided in example 1 at different rotational speeds in 0.1mol/L KOH solution; the inset is the corresponding K-L curve, and the electron transfer number in the ORR process is calculated to be 4;

FIG. 20 shows non-noble metal electrocatalysts as provided in example 1 in N₂Saturated, O₂Cyclic voltammograms in saturated 0.1mol/L KOH solution;

FIG. 21 is a comparison of the methanol resistance of the non-noble metal electrocatalyst and the 20% Pt/C catalyst provided in example 1, showing the i-t curves for the two catalysts before and after methanol addition, respectively;

FIG. 22 is a comparison of the stability of the non-noble metal electrocatalyst provided in example 1 and a commercial 20% Pt/C catalyst in 0.1mol/L KOH solution versus the LSV curves for the two catalysts after 5000 CV cycles;

FIG. 23 is a comparison of the electrocatalytic hydrogen evolution performance of the non-noble metal electrocatalyst provided in example 1, the porous biomass charcoal catalyst provided in comparative examples 1-2, and the 20% Pt/C catalyst in 1mol/L KOH.

Detailed Description

The invention is further illustrated by the following examples. These examples are intended to illustrate the invention and are not intended to limit the scope of the invention. Experimental procedures without specific conditions noted in the examples below, generally according to conditions conventional in the art or as suggested by the manufacturer; the raw materials, reagents and the like used are, unless otherwise specified, those commercially available from the conventional markets and the like. Any insubstantial changes and substitutions made by those skilled in the art based on the present invention are intended to be covered by the claims.