阅读说明：本技术 一种电化学还原二氧化碳制合成气的催化剂及其制备方法 (Catalyst for preparing synthesis gas by electrochemical reduction of carbon dioxide and preparation method thereof ) 是由 张世国 倪文鹏 张妍 于 2020-08-07 设计创作，主要内容包括：本发明涉及一种电化学还原二氧化碳制合成气的催化剂及其制备方法与其在二氧化碳电化学还原中的应用,属于二氧化碳资源化利用和储能技术领域。该催化剂由含金属原子M1的层级孔结构的碳载体负载含金属原子M2的分子催化剂制得。所述的碳载体,由金属离子交联的聚乙烯基咪唑结合二氧化硅纳米球硬模板高温碳化后,经碱洗制得,然后负载分子催化剂。本发明的催化剂,通过改变载体和分子催化剂中金属中心原子的种类实现对氢析出反应和二氧化碳还原反应的选择性进行调控,并结合电解液和电位的改变实现对生成的合成气中H<Sub>2</Sub>/CO的比例调变。该方法具有良好的适用性,操作简单易于放大生产,具有良好的应用前景。(The invention relates to a catalyst for preparing synthesis gas by electrochemically reducing carbon dioxide, a preparation method thereof and application thereof in electrochemical reduction of carbon dioxide, and belongs to the technical field of resource utilization and energy storage of carbon dioxide. The catalyst is prepared by loading a molecular catalyst containing a metal atom M2 on a carbon carrier containing a hierarchical pore structure of the metal atom M1. The carbon carrier is prepared by carbonizing a hard template of metal ion crosslinked polyvinyl imidazole combined silicon dioxide nanospheres at high temperature, washing with alkali and then loading a molecular catalyst. The catalyst realizes regulation and control of selectivity of hydrogen evolution reaction and carbon dioxide reduction reaction by changing species of metal central atoms in the carrier and the molecular catalyst, and realizes regulation and control of H in generated synthesis gas by combining change of electrolyte and potential 2 The ratio of/CO is modulated. The method has good applicability, simple operation, easy amplification production and good application prospect.)

1. The catalyst for preparing the synthesis gas by electrochemically reducing the carbon dioxide is characterized by consisting of a carbon carrier containing a single metal atom M1 and a molecular catalyst loaded with a metal atom M2; the M1 atom is one or more of iron, cobalt, nickel, copper, zinc, aluminum, chromium, manganese, silver, ruthenium, indium, tin and bismuth.

2. The catalyst for preparing synthesis gas by electrochemically reducing carbon dioxide as claimed in claim 1, wherein the molecular catalyst containing the atom M2 is a molecular catalyst of phthalocyanine, porphyrin or vitamin B12 of one or more of iron, cobalt, copper and manganese.

3. The catalyst for preparing synthesis gas by electrochemically reducing carbon dioxide as recited in claim 1, wherein the mass ratio of the carbon support of the monatomic M1 to the supported molecular catalyst is: 10:1-1:10.

4. The catalyst for preparing synthesis gas by electrochemical reduction of carbon dioxide as claimed in claim 1, wherein the carbon support containing M1 is prepared by alkali washing after carbonizing hard templates of metal ion crosslinked polyvinyl imidazole combined silica nanospheres at high temperature.

5. The catalyst for preparing synthesis gas by electrochemical reduction of carbon dioxide as claimed in claim 4, wherein the temperature of the high temperature carbonization is 910-1050^oAnd C, the reaction atmosphere is argon.

6. The method for preparing a catalyst for synthesis gas by electrochemical reduction of carbon dioxide as claimed in claim 1, wherein the molecular catalyst is supported by wet high-temperature treatment or physical mixing.

7. The method according to claim 6, wherein the wet high-temperature treatment is carried out using N, N-dimethylformamide as a solvent; the physical mixing means include grinding and ball milling.

8. Electrochemical reduction of CO using the catalyst obtained by the method of claim 6₂The application in preparing synthesis gas is characterized in that the catalystThe catalyst is used as a catalytic electrode to participate in electrochemical reduction of CO₂Preparing synthesis gas; the preparation process of the catalytic electrode comprises the following steps: the catalyst powder and the Nafion binder are dispersed in the dispersant by ultrasonic wave and then directly coated on the carbon paper by dropping and dried.

9. The application of claim 8, wherein the dispersant is a mixture of one or more of ethanol, isopropanol and ethylene glycol with water; the volume ratio of the Nafion binder to the dispersing agent is 1: 19; the catalyst concentration in the catalyst slurry is 1-10 mg/mL.

10. The use of claim 8, wherein the drying temperature is 50-100 deg.f^oC。

Technical Field

The invention relates to a catalyst for preparing synthesis gas by electrochemically reducing carbon dioxide, a preparation method thereof and application thereof in electrochemical reduction of carbon dioxide, and belongs to the technical field of resource utilization and energy storage of carbon dioxide.

Background

Carbon dioxide (CO)₂) The resource utilization of the method is an important means for relieving the problems of increasingly severe energy shortage and environmental pollution. Wherein the sustainable energy-driven electrochemical reduction converts CO₂Conversion to high value-added chemicals and fuels is a technology that is of great interest. However, as the reaction conditions change, CO₂Can be reduced to various compounds including carbon monoxide (CO), formic acid (HCOOH), acetic acid (CH)₃COOH), methane (CH)₄) Ethylene (C)₂H₄) Methanol (CH)₃OH) and ethanol (CH)₃CH₂OH), etc., which makes it difficult to prepare a certain product, particularly C2+ species, with high selectivity. On the other hand, the CO content in the aqueous electrolyte₂The low solubility of the molecule makes the current density to produce a single product low for practical use. In view of this, hydrogen gas (H) generated by the Hydrogen Evolution Reaction (HER) which is unavoidable in the aqueous electrolyte system is utilized₂) By combining with CO₂Reduction to CO to give a product having a different H₂And CO ratio (H)₂CO) is another more feasible route. Considering the wide application of the synthesis gas in industrial productionIn the way, and the existing mature production process based on the synthesis gas, the path has the advantages of strong applicability, simple production line construction, low cost and the like.

Realizing high-efficiency CO₂The key to the reduction of syngas is the design with CO₂Bifunctional catalyst for reduction and HER activity, and combined with regulation of active components and design of electrolyte, preparation of catalyst with wide H under high current density₂Syngas in a/CO ratio. At present, noble metal-based catalysts such as gold (Au), or other metal alloy catalysts are capable of achieving syngas H₂Control of/CO, but the current density is still low. At the same time, metal chalcogenides also exhibit good catalytic CO₂The capability of converting into synthesis gas, but the preparation process is difficult to scale up and produce on a large scale, and practical application is restricted (Angew. chem. int. Ed. 2017, 129, 9249-9253). Heteroatom-doped carbon materials as CO, on the other hand₂Reduced catalysts have received extensive attention, especially with monatomic metal site-doped carbon materials exhibiting excellent CO selectivity. The composition of such materials and the designability of the pore structure provide for the tunability of the reduction product and current density. In view of this, a set of bifunctional carbon-based single-atom catalysts for efficiently generating synthesis gas is developed, and the preparation method is simplified, so that the method has a very wide application prospect.

Disclosure of Invention

In order to solve the technical problem, the invention develops a catalyst with CO₂The catalyst is prepared by a single M1 metal-doped carbon carrier loaded molecular catalyst containing M2 metal, and the single M1 atom-containing carbon carrier is obtained by carbonizing polyvinyl imidazole cross-linked by M1 metal ions and zinc ions as a precursor in an inert atmosphere. The invention also provides a preparation method of the catalyst, and the method is simple and easy to operate and is suitable for industrial production. Finally, the catalyst is used for electrochemical reduction of carbon dioxide, and can prepare H with wide range under high current density₂Syngas in a/CO ratio.

The technical scheme adopted by the invention is as follows:

a catalyst for preparing synthesis gas by electrochemically reducing carbon dioxide, wherein the catalyst consists of a carbon carrier containing a single metal atom M1 and a molecular catalyst containing a metal atom M2; the M1 atom is one or more of iron, cobalt, nickel, copper, zinc, aluminum, chromium, manganese, silver, ruthenium, indium, tin and bismuth.

Preferably, the molecular catalyst containing the atom M2 is a phthalocyanine, porphyrin or vitamin B12 molecular catalyst containing one or more of iron, cobalt, copper and manganese.

Preferably, the content of M1 on the carbon carrier containing the single atom M1 is 0.5-2.0 wt%; the mass ratio of the carbon carrier of the monoatomic M1 to the supported molecular catalyst is as follows: 10:1-1:10.

Preferably, the carbon carrier containing the monoatomic M1 is prepared by carbonizing a hard template of a polyvinyl imidazole-bonded silica nanosphere crosslinked by metal ions at high temperature and then washing with alkali.

Preferably, the temperature of the high-temperature carbonization is 910-1050^oAnd C, the time is 1-4 h, and the reaction atmosphere is argon.

The preparation method of the catalyst for preparing the synthesis gas by electrochemically reducing the carbon dioxide adopts a wet high-temperature treatment or physical mixing mode to load the molecular catalyst.

Preferably, the wet high-temperature treatment takes N, N-dimethylformamide as a solvent; the physical mixing means include grinding and ball milling.

The catalyst prepared by the preparation method is used for electrochemically reducing CO₂Application of catalyst in preparation of synthesis gas, and catalyst used as catalytic electrode to participate in electrochemical reduction of CO₂Preparing synthesis gas; the preparation process of the catalytic electrode comprises the following steps: the catalyst powder and the Nafion binder are dispersed in the dispersant by ultrasonic wave and then directly coated on the carbon paper by dropping and dried.

Preferably, the dispersant is a mixture of one or more of ethanol, isopropanol and ethylene glycol and water; the volume ratio of the Nafion binder to the dispersing agent is 1: 19; the concentration of the catalyst in the catalyst slurry is 1-10 mg/mL; the drying temperature is 50-100 DEG C^oC。

The catalyst provided by the invention is subjected to electrochemical test in a three-electrode system: the electrode carrying the catalyst is a working electrode, the Pt net is a counter electrode, and Ag/AgCl is a reference electrode. The electrolyte is KHCO₃An aqueous solution. The electrolytic cell comprises an H-shaped double-chamber electrolyte and a flow type electrolytic cell. The electrolyte concentration is 0.1 to 1M.

The single M1 atom carbon carrier provided by the invention is obtained by carbonizing a polyvinyl imidazole cross-linked by metal ions as a precursor in an inert atmosphere, and the specific method comprises the following steps: vinyl imidazole is polymerized under the initiation of azodiisobutyronitrile, the solvent is N, N-dimethylformamide, polyvinyl imidazole is prepared after reaction, the polyvinyl imidazole is dissolved in ethanol and then mixed with silicon dioxide nanospheres, and then the mixture is mixed with ethanol solution of corresponding metal ions to obtain a crosslinked polyvinyl imidazole precursor. The precursor is carbonized in a tube furnace under the argon atmosphere, then is treated in concentrated alkali solution to remove silicon dioxide nanospheres, and is washed and dried to obtain the single M1 atom carbon carrier.

The carbon-based single-atom catalyst provided by the invention is prepared by loading a molecular catalyst containing M2 metal on a single M1 metal carbon carrier, and the preparation method comprises the following two steps: one is carbon carrier and molecular catalyst dispersed in N, N-dimethyl formamide in certain proportion in 90%^oC, removing the solvent and drying after treatment; the other is that a certain proportion of carbon carrier is directly and physically mixed with molecular catalyst. CO provided by the invention₂The reduction catalyst electrode was prepared as follows: adding a dispersant into an M2 molecular catalyst loaded by a single M1 atomic carbon carrier, adding a Nafion binder, and then uniformly dispersing by ultrasonic oscillation to obtain catalyst slurry; coating the slurry on carbon paper and drying to obtain the catalytic electrode.

The invention discloses a method for preparing different H by carbon dioxide electroreduction₂A carbon-based single metal atom catalyst of synthetic gas with a/CO ratio and a preparation method thereof. The catalyst is prepared by loading a molecular catalyst containing a metal atom M2 on a carbon carrier containing a hierarchical pore structure of the metal atom M1. The carbon carrier of the monoatomic M1 is prepared by carbonizing polyvinyl imidazole crosslinked by metal ions at high temperature and is combined with a silica nanosphere hard template to obtain the catalystTo a carbon support having macropores, mesopores and micropores at the same time. The carrier can be directly used as a carbon dioxide electro-reduction catalyst after being combined with a molecular catalyst in a simple physical mixing mode and the like.

The invention has the advantages of

1. In a wide range to the H in the generated synthesis gas₂Modulation of the ratio of/CO

The catalyst provided by the invention can realize regulation and control of selectivity of hydrogen evolution reaction and carbon dioxide reduction reaction by changing the species of metal central atoms in the carrier and the molecular catalyst, and realizes H in generated synthesis gas in a wider range by combining with the change of electrolyte and potential₂The ratio of/CO is modulated to obtain H₂Synthesis gas with a/CO ratio of 0.2 to 30 and at high current density giving a synthesis gas with ideal H for direct Fischer-Tropsch synthesis₂Syngas in a/CO ratio (e.g. in H-type cells at above 220 mA cm^-2Current density of (D) to obtain H₂Syngas with a CO ratio of 3).

2. Good applicability and suitability for industrialization

The method has good applicability to various metal ions, has cheap raw materials and wide sources, is simple to operate, is easy to amplify and produce, and has good application prospect in the fields of preparing synthesis gas from electrochemical carbon dioxide and other fields.

Drawings

FIG. 1 is a scanning electron microscope and nitrogen desorption test of a monoatomic Co carbon support in example 1 of the present invention, and the obtained pore size distribution curve (FIG. 1 a) and an image of a transmission electron microscope (FIG. 1 b) with spherical aberration correction.

FIG. 2 shows the total current density (FIG. 2 a) and H in the reduction product at different potentials for the catalytic electrode of example 2₂the/CO ratio (FIG. 2 b).

FIG. 3 shows the total current density (FIG. 3 a) and H in the reduction product at different potentials for the catalytic electrode of example 3₂the/CO ratio (FIG. 3 b).

FIG. 4 shows the total current density (FIG. 4 a) and H in the reduction product at different potentials for the catalytic electrode of example 4₂Ratio of (C to COFig. 4 b).

FIG. 5 shows the total current density (FIG. 5 a) and H in the reduction product at different potentials for the catalytic electrode of example 5₂the/CO ratio (FIG. 5 b).

FIG. 6 shows the total current density (FIG. 6 a) and H in the reduction product at different potentials for the catalytic electrode of example 6₂the/CO ratio (FIG. 6 b).

FIG. 7 shows the total current density (FIG. 7 a) and H in the reduction product for the catalytic electrode of example 7 at different potentials₂the/CO ratio (FIG. 7 b).

FIG. 8 shows the total current density (FIG. 8 a) and H in the reduction product for the catalytic electrode of example 8 at different potentials₂the/CO ratio (FIG. 8 b).

The specific implementation mode is as follows:

for a better understanding of the present invention, the following examples are set forth in order to provide a further understanding of the present invention, and are not to be construed as limiting the present invention in any way.