Preparation method of diatomite composite catalytic material

Abstract

The present application relates to composite material catalysis technology, and aims to provide a preparation method of diatomite composite catalytic material.The method comprises the following steps: after diatomite is modified by acid immersion, the modified diatomite is used for hydrothermal reaction to load noble metal active component, and the reaction system comprises a noble metal nitrate aqueous solution, modified diatomite and appropriate distilled water; the reaction product is subjected to suction filtration, washing and drying, and then is calcined by an ink method or a joule heat method to obtain carbon paper which can be used as an electrode and on which the diatomite composite catalytic material is loaded.The diatomite composite catalyst used in the present application can effectively realize electrocatalytic reduction of carbon dioxide to carbon monoxide, has good conversion efficiency and carbon monoxide yield; the composite catalyst has a developed pore structure and a large specific surface, which is helpful for carbon dioxide capture and diffusion, and the rough carrier surface is beneficial to uniform dispersion of the loaded noble metal, realizes nanoscale growth of the metal component, and comprehensively improves reaction mass transfer and catalytic activity.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite material catalysis, and particularly relates to a preparation method of diatomite composite catalytic material. BACKGROUND

[0002] The massive use of fossil fuels has caused serious air pollution, climate warming and energy crisis, and the development of clean renewable energy has become a top priority. In order to achieve carbon emission reduction and full use of renewable energy, energy conversion and storage technologies represented by electrocatalytic reduction of carbon dioxide are crucial. High-activity electrocatalysts are the key to efficient reduction of CO2.

[0003] Among various heterogeneous catalysts involved, noble metal catalysts such as Pt, Pd, Au, Ag and the like show significant low-temperature catalytic activity. However, due to the high cost of noble metals, the catalysts developed with noble metals are very limited in practical conditions. The introduction of supported catalysts provides a practical way to solve the above-mentioned contradiction. By selecting appropriate supports, the growth of supported metals can be effectively controlled and the synergistic catalytic performance of the overall catalyst can be improved, thereby achieving the goal of efficient and low-cost synergistic catalysis.

[0004] At present, the supports used by industrial catalysts include molecular sieves, honeycomb ceramics, activated carbon, zeolites, montmorillonite, porous foam metal, diatomite and kaolin, etc. China has abundant reserves of high-quality diatomite, such as Jilin Changbai Mountain, Quzhou City, Zhejiang, etc., which have different forms of diatomite output, and the cost is low, which is a very good choice of carrier. Obviously, making full use of the local diatomite resource advantage and using easily available diatomite as a carrier can effectively reduce the high cost of the catalyst.

[0005] Diatomite is a biogenic siliceous sedimentary rock composed of amorphous SiO2, which has many practical advantages and is a suitable industrial catalyst support. For example, diatomite has a unique microporous structure, which can effectively help capture and diffuse carbon dioxide as a support, thereby improving the mass transfer of the reaction. Diatomite itself has a large specific surface area, providing numerous sites for the loading of noble metal catalysts, and is expected to grow nanocatalysts through reaction condition control. Diatomite has good adsorption properties, and as a catalyst carrier it can effectively adsorb carbon dioxide, which helps to contact and activate the reactants with the active sites of the catalyst. Diatomite itself has a SiO2 content of more than 98% after modification and screening, and has good thermal stability, which helps to improve the stability of the catalyst. Diatomite itself does not contain chemical toxic substances, and as a catalyst carrier for catalytic reduction reactions, it will not release toxic substances, which is green and environmentally friendly.

[0006] However, although diatomite has the above advantages, it still has certain disadvantages when used as a catalyst carrier in specific application scenarios. For example, the diatomite mineral has many impurities (such as viscosity, etc.), and it is difficult to achieve fine regulation of the loading of the metal active component in the catalyst; the diatomite from different places has great differences in morphology, which leads to differences in the main parameter indexes of the carrier, such as porosity and mechanical strength, and affects the loading regulation of the metal active component, thereby affecting the performance of the catalytic material; in the aqueous solution environment, there are a large number of silicon hydroxyl groups on the surface and micropores of diatomite, and there are hydrogen bonds, which exhibit hydrophilicity, which inhibits the yield of CO and is not conducive to the generation of high-purity carbon products.

[0007] Therefore, it is necessary to further modify the diatomite raw material for the preparation of catalytic materials to meet the technical requirements of more application scenarios. SUMMARY

[0008] The technical problem to be solved by the present application is to overcome the deficiencies in the prior art and provide a preparation method of diatomite composite catalytic material.

[0009] To solve the technical problem, the solution of the present application is:

[0010] A preparation method of diatomite composite catalytic material is provided, comprising the following steps:

[0011] (1) Acid leaching modification treatment of diatomite

[0012] The crushed diatomite raw ore is added to an acid solution and subjected to acid leaching treatment under stirring; after natural sedimentation, the precipitate is taken out, washed by centrifugation with distilled water, mixed with an alkali solution, and the pH value is adjusted to weak alkalinity; the obtained mixture is fully dispersed, sieved and dried to obtain modified diatomite;

[0013] (2) Loading of noble metal active component

[0014] A noble metal nitrate aqueous solution, modified diatomite and an appropriate amount of distilled water are mixed and ultrasonically treated at room temperature; the mixture is moved to a reaction kettle, sodium citrate solution is added under stirring, and the reaction kettle is sealed for hydrothermal reaction; in the hydrothermal reaction system, the mass ratio of noble metal element: modified diatomite: water: sodium citrate is 0.4-10.8: 100: 8: 1.03-103; after the reaction is completed, the reaction product is suction filtered, washed, and the solid is dried to obtain a catalyst semi-finished product;

[0015] (3) Activation of composite catalytic material

[0016] The activation treatment of the composite catalytic material is carried out in any of the following ways:

[0017] (3.1) The catalyst semi-finished product is ground into powder and added to a mixture of distilled water, ethanol, and phenol for ultrasonic dispersion; the dispersion is dropped onto one side of a hydrophobic carbon paper, dried at room temperature to obtain the carbon paper used as an electrode, on which diatomaceous earth composite catalyst material is loaded; or,

[0018] (3.2) Grind the catalyst semi-finished product into powder and add it to distilled water or ethanol solution for dispersion; take the dispersion and drop it onto one side of the surface of hydrophobic carbon paper, dry it at room temperature, and then calcine it using the Joule heating method to obtain carbon paper that can be used as an electrode. Diatomaceous earth composite catalyst material is loaded on the carbon paper.

[0019] As a preferred embodiment of the present invention, in step (1), the acid solution is a hydrochloric acid solution, nitric acid solution, sulfuric acid solution or citric acid solution with a concentration of 1 to 3 mol / L, and the temperature of the acid leaching treatment is 20 to 100°C and the time is 1 to 3 hours; the alkaline solution is a potassium hydroxide solution with a concentration of 2 mol / L.

[0020] As a preferred embodiment of the present invention, in step (1), the number of centrifugal washings is 3 times, and the pH value is adjusted to 9-10; the monomer structure length of the modified diatomite after sieving and drying is 8-15 μm.

[0021] As a preferred embodiment of the present invention, in step (2), the precious metal element is at least one of palladium, silver, ruthenium or rhodium; the concentration of the precious metal nitrate aqueous solution is 0.001 to 0.025 mol / L, and the concentration of the sodium citrate solution is 0.002 to 0.2 mol / L.

[0022] As a preferred embodiment of the present invention, in step (2), when mixing the precious metal nitrate aqueous solution, modified diatomaceous earth and distilled water, the mixture is first ultrasonically treated for 10 min, and then stirred at room temperature for 20 to 40 min; when adding sodium citrate solution, the stirring speed is maintained at 500 to 900 rpm; the hydrothermal reaction temperature is 130 to 150°C, and the time is 3 to 5 h.

[0023] As a preferred embodiment of the present invention, in step (2), the reaction product is filtered and washed several times with distilled water and ethanol, and the resulting solid is dried in an oven at 60°C for 5-7 hours.

[0024] As a preferred embodiment of the present invention, in step (3), the ultrasonic dispersion time is 2 hours.

[0025] In a preferred embodiment of the present invention, in step (3), the amount of dispersion added is controlled so that the loading of the noble metal active component on the carbon paper is 0.01–0.27 mg / cm³. 2 .

[0026] As a preferred scheme of the present application, in step (3.2), during the calcination by the Joule heating method, the parameters are controlled as follows: 20-60V, 5-10A, 0.01-0.05s, one-time pulse current conduction.

[0027] The present application further provides an application method of the carbon paper loaded with the diatomite composite catalytic material prepared by the aforementioned method in electrocatalytic reduction of CO2, which is used as a working electrode, together with an Ag / AgCl reference electrode and a platinum plate counter electrode to form a three-electrode system; a KHCO3 solution is used as an electrolyte, and the overpotential and current density of the catalyst are obtained through an electrochemical workstation, so that CO2 gas is reduced to CO.

[0028] Invention principle description:

[0029] The diatomite composite catalytic material provided by the present application has the characteristics of high activity and high stability, and has a relatively low content of noble metal active components and non-noble metal additives. The developed pore structure can effectively capture carbon dioxide in the air, and can effectively convert carbon dioxide and water into a mixed gas of carbon monoxide and hydrogen at room temperature without heating or illumination, and is suitable for various carbon dioxide conversion and energy storage devices. In addition, the preparation method adopted by the present application is simple and easy to operate, has strong universality, and the raw materials are cheap and easy to obtain, and is suitable for large-scale preparation of industrial catalysts.

[0030] Diatomite usually has a unique regional appearance feature, which may exhibit different porosity and adsorption characteristics. Diatomite with excellent characteristics and few inferior qualities is rare. Therefore, in order to expand the market application of various diatomite raw materials and improve their commodity value, it is necessary to perform comprehensive modification and screening processes such as acid leaching, alkali neutralization and sieving on diatomite with special structure, low purity and high clay impurity, so as to remove impurity minerals, etch to increase the surface roughness of diatomite, and remove agglomerated clay blocks and small fragments. The comprehensive process is used to help obtain diatomite with high purity and special morphology, which is beneficial to the loading and morphology control of noble metal active components.

[0031] On the basis of modifying diatomite, the present application further realizes uniform loading of noble metal on diatomite with special morphology through a simple and easy synthetic process method; while maintaining the conversion efficiency of the catalyst in electrocatalytic reduction of carbon dioxide and water into carbon monoxide and hydrogen, the use amount of noble metal is greatly reduced, and the cost of the catalyst is significantly reduced.

[0032] By adjusting the process parameters, the present application can realize nanoscale size regulation of the metal loaded on diatomite, so as to effectively control the ratio of carbon monoxide and hydrogen generated by electrocatalytic reduction, and be applied to different environmental requirements.

[0033] Compared with the prior art, the present application has the following beneficial effects:

[0034] 1、The diatomite composite catalyst used in the present application can effectively realize the electrocatalytic reduction of carbon dioxide to carbon monoxide, and has good conversion efficiency and carbon monoxide yield.

[0035] 2、The diatomite composite catalyst prepared in the present application has developed pore structure and large specific surface area, which is helpful for carbon dioxide capture and diffusion on the one hand, and the rough carrier surface is beneficial to the uniform dispersion of noble metal loading, realizing the nanoscale growth of metal components, and comprehensively improving the reaction mass transfer and catalytic activity.

[0036] 3、The preparation process disclosed in the present application has simple flow and high repeatability, and through simple experimental parameter adjustment, the nanoscale morphology regulation of noble metal loading can be effectively completed, and the proportion control of carbon monoxide and hydrogen generated in the application of the catalyst in the carbon dioxide-containing water environment can be realized.

[0037] 4、The diatomite composite catalyst used in the present application greatly reduces the amount of noble metal used, significantly reduces the cost, has environmental friendliness and good thermal stability, and is more suitable for industrial scale preparation. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The SEM morphology of the diatomite composite catalyst material described in the present application is shown in the figure.

[0039] The magnification of each area in the figure is: (a) 100 times, (b) 500 times, (c) 5000 times, and (d) 10000 times. DETAILED DESCRIPTION

[0040] In order to clearly and completely describe the technical solutions in the embodiments of the present application, it is obvious that the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0041] First part of the implementation scheme of the present application

[0042] The preparation method of the diatomite composite catalyst material provided by the present application comprises the following steps:

[0043] (1) Acid leaching modification treatment of diatomite

[0044] The broken diatomite raw ore is added into a hydrochloric acid solution, a nitric acid solution, a sulfuric acid solution or a citric acid solution with a concentration of 1-3 mol / L, and is subjected to acid leaching treatment at 20-100 ℃ under stirring for 1-3 h; after natural sedimentation, the precipitate is taken out, washed with distilled water by centrifugation for 3 times, mixed with a potassium hydroxide solution with a concentration of 2 mol / L, and adjusted to weak alkalinity (pH value to 9-10); the obtained mixture is fully dispersed, screened and dried to obtain modified diatomite with a monomer structure length of 8-15 μm;

[0045] (2) Loading of noble metal active component.

[0046] The noble metal nitrate aqueous solution, the modified diatomite and an appropriate amount of distilled water are first subjected to ultrasonic treatment for 10 min, and then kept stirring at room temperature for 20-40 min; the noble metal element can be at least one of palladium, silver, ruthenium and rhodium; the concentration of the noble metal nitrate aqueous solution can be selected as 0.001-0.025 mol / L. Then the mixture is moved to a reaction kettle, a sodium citrate solution with a concentration of 0.002-0.2 mol / L is added under stirring at a speed of 500-900 rpm, and then the reaction kettle is sealed for hydrothermal reaction, the reaction temperature is 130-150 ℃, and the time is 3-5 h; in the raw materials for hydrothermal reaction, the mass ratio of noble metal element: modified diatomite: water: sodium citrate is 0.4-10.8: 100: 8: 1.03-103. After the reaction is completed, the reaction product is suction filtered, washed with distilled water and ethanol several times respectively, and the obtained solid is placed in a 60 ℃ oven for drying for 5-7 h to obtain a catalyst semi-product;

[0047] (3) Activation of composite catalytic material

[0048] The activation treatment of the composite catalytic material is carried out in any of the following ways:

[0049] (3.1) The catalyst semi-product is ground into powder, added into a distilled water-ethanol-phenol mixed solution, and subjected to ultrasonic dispersion for 2 h; the dispersion liquid is dropped onto one side surface of a hydrophobic carbon paper, and the dropping amount of the dispersion liquid is controlled so that the loading amount of the noble metal active component on the carbon paper is 0.01-0.27 mg / cm 2 . After drying at room temperature, the carbon paper capable of being used as an electrode is obtained, and the diatomite composite catalytic material is loaded on the carbon paper; or,

[0050] (3.2) The catalyst semi-product is ground into powder, added into a distilled water or ethanol solution, and subjected to ultrasonic dispersion for 2 h; the dispersion liquid is dropped onto one side surface of a hydrophobic carbon paper, and the dropping amount of the dispersion liquid is controlled so that the loading amount of the noble metal active component on the carbon paper is 0.01-0.27 mg / cm 2After drying at room temperature, the calcination is carried out by Joule heat method, with the parameters controlled as 20-60V, 5-10A, 0.01-0.05s, one pulse current conduction. The carbon paper capable of being used as an electrode is finally obtained, and the diatomite composite catalytic material is loaded on the carbon paper.

[0051] In the above activation process, different electrode preparation methods are adopted. Among them, method (3.1) is the mainstream ink method, in which ultrasonic treatment can help the catalyst to be fully dispersed on the conductive carbon paper, and the phenol in the mixed solution can serve as a solidification cross-linking effect to make the catalyst and the conductive carbon paper continuously produce physical contact, thereby activating the catalyst to prepare the electrode. Method (3.2) is to use the Joule heat method for calcination, and the catalyst and the conductive carbon paper are contacted and sintered by the method of rapid temperature rise and fall, which can also achieve the effect of activating the catalyst.

[0052] Further, the carbon paper can be used as a working electrode, together with an Ag / AgCl reference electrode and a platinum sheet counter electrode to form a three-electrode system; a KHCO3 solution is used as an electrolyte, and the overpotential and current density of the catalyst are obtained by an electrochemical workstation, so that the CO2 gas is reduced to CO.

[0053] Second part of the specific embodiment of the present application

[0054] Example 1

[0055] The diatomite composite catalytic material provided in this example contains 1g of modified diatomite carrier and 0.00004mol of active component Pd.

[0056] The preparation method is as follows:

[0057] S1, modification of diatomite.

[0058] First step: prepare a 1mol / L hydrochloric acid solution, and weigh the crushed diatomite ore into the above acid solution and stir at 100℃ for 2h.

[0059] Second step: remove the solution by natural deposition of the solid-liquid mixture obtained in the first step, and centrifugally wash with distilled water for 3 times, and add 2mol / L sodium hydroxide solution dropwise to adjust the pH value to 10.

[0060] Third step: after the solid-liquid mixture obtained in the second step is fully dispersed, it is sieved through 500 mesh, 1000 mesh, 1600 mesh and 2000 mesh sieves in turn, and the sieve product on the 1600 mesh sieve is put into an oven for drying, to obtain a large amount of single diatomite structure carrier with a length of 8-15μm, for standby use.

[0061] S2, loading of noble metal active component.

[0062] Step 1: Prepare a 0.001 mol / L palladium nitrate solution and a 0.002 mol / L sodium citrate solution.

[0063] Step 2: Transfer 40 ml of palladium nitrate solution, 1 g of modified carrier and 20 ml of distilled water into a 100 ml beaker, sonicate for 10 min and then stir at room temperature for 30 min.

[0064] Step 3: Transfer the above solution to a stirred and heated reactor, maintain a stirring speed of 500 rpm, slowly add 20 ml of sodium citrate solution dropwise to the above mixture, seal the reactor, and heat to 150°C for 5 hours.

[0065] In the hydrothermal reaction system, the mass ratio of precious metal element: modified diatomaceous earth: water: sodium citrate is 0.43:100:8:1.03;

[0066] Step 4: Filter the mixture in the reactor, wash it several times with distilled water and ethanol respectively, and dry the resulting solid in a 60°C oven for 6 hours to obtain a catalyst semi-finished product.

[0067] S3, Electrode preparation.

[0068] The synthesized catalyst semi-finished product was lightly ground into powder. 10 mg of the powder was ultrasonically dispersed with 20 μl of distilled water, 60 μl of ethanol solution, and 20 μl of phenol solution for 2 hours. Then, 10 μl of the mixture was dropped onto one side of a 0.7 cm x 0.7 cm hydrophobic carbon paper. The amount of drop was controlled to ensure that the loading of the noble metal active component on the carbon paper was 0.05 mg / cm². 2 After drying at room temperature, carbon paper loaded with diatomaceous earth composite catalyst material is obtained.

[0069] Example 2

[0070] The diatomite composite catalytic material provided in this embodiment contains 1g of modified diatomite support and 0.0001mol of active component Ag.

[0071] Its preparation method is as follows:

[0072] S1, diatomaceous earth modification.

[0073] Step 1: Prepare a 2 mol / L hydrochloric acid solution. Weigh the crushed diatomaceous earth ore into the acidic solution and stir at 80°C for 3 hours.

[0074] Step 2: Allow the solid-liquid mixture obtained in Step 1 to settle naturally to remove the solution, then mix with distilled water and centrifuge three times to wash. Add 2 mol / L sodium hydroxide solution to the suspension to adjust the pH to 10.

[0075] Third step: the solid-liquid mixture obtained in the second step is dispersed thoroughly and then sieved through 500 mesh, 1000 mesh, 1600 mesh and 2000 mesh sieves in turn, and the sieve product on the 1600 mesh sieve is put into an oven for drying to obtain a large amount of carriers with a single diatomite structure length of 8-15 μm for standby use.

[0076] S2, loading of noble metal active component.

[0077] First step: preparation of 0.0025 mol / L silver nitrate solution and 0.01 mol / L sodium citrate solution.

[0078] Second step: 40 ml of silver nitrate solution, 1 g of modified carrier and 20 ml of distilled water solution are transferred into a 100 ml beaker, ultrasonic treatment is performed for 10 min, and then room temperature stirring is performed for 20 min.

[0079] Third step: the above solution is transferred into a stirring and heating reaction kettle, the stirring speed is kept at 500 rpm, 20 ml of sodium citrate solution is slowly added into the above mixture, the reaction kettle is closed, heated to 130℃ and reacted for 5 h.

[0080] In the hydrothermal reaction system, the mass ratio of noble metal element: modified diatomite: water: sodium citrate is 1.08: 100: 8: 5.16;

[0081] Fourth step: the mixture in the reaction kettle is filtered, washed with distilled water and ethanol several times, and the obtained solid is placed in a 60℃ oven for drying for 5 h to obtain a catalyst semi-finished product.

[0082] S3, electrode preparation.

[0083] The synthesized catalyst semi-finished product is slightly ground into powder, 10 mg of which is ultrasonically dispersed with 20 μl of distilled water, 60 μl of ethanol solution and 20 μl of phenol solution for 2 h, and then 10 μl of the mixture is added dropwise to one side surface of a 0.7 cm*0.7 cm hydrophobic carbon paper; the dropwise amount is controlled so that the loading amount of noble metal active component on the carbon paper is 0.17 mg / cm 2 . After waiting for room temperature drying, a carbon paper loaded with diatomite composite catalytic material is obtained.

[0084] Example 3

[0085] This example provides a diatomite composite catalytic material, which comprises 1 g of modified diatomite carrier and 0.00004 mol of active component Ru.

[0086] The preparation method is as follows:

[0087] S1, diatomite modification.

[0088] First step: prepare 3 mol / L hydrochloric acid solution, and weigh the broken diatomite ore into the above acid solution, and stir at 20℃ for 3h.

[0089] Second step: remove the solution by natural deposition of the solid-liquid mixture obtained in the first step, and centrifugal wash with distilled water for 3 times. Add 2 mol / L sodium hydroxide solution dropwise to the suspension to adjust the pH value to 10.

[0090] Third step: after the solid-liquid mixture obtained in the second step is fully dispersed, it is sieved through 500 mesh, 1000 mesh, 1600 mesh and 2000 mesh sieves in turn, and the sieve product on the 1600 mesh sieve is placed in an oven for drying to obtain a large number of diatomite carriers with a single structure length of 8-15 μm, which are ready for use.

[0091] S2, loading of noble metal active component.

[0092] First step: prepare 0.001 mol / L ruthenium nitrate solution and 0.008 mol / L sodium citrate solution.

[0093] Second step: take 40 ml of ruthenium nitrate solution, 1 g of modified carrier and 20 ml of distilled water solution into a 100 ml beaker, and ultrasonic for 10 min, then stir at room temperature for 30 min.

[0094] Third step: transfer the above solution into a stirring and heating reaction kettle, keep the stirring speed at 700 rpm, slowly drop 20 ml of sodium citrate solution into the above mixture, close the reaction kettle, heat to 150℃ and react for 5h.

[0095] In the hydrothermal reaction system, the mass ratio of noble metal element: modified diatomite: water: sodium citrate is 0.40: 100: 8: 4.12;

[0096] Fourth step: filter the mixture in the reaction kettle, wash with distilled water and ethanol several times respectively, and dry the obtained solid in a 60℃ oven for 7h to obtain a catalyst semi-finished product.

[0097] S3, electrode preparation.

[0098] The synthesized catalyst semi-finished product is slightly ground into powder, which is dispersed on one side surface of hydrophobic carbon paper by ultrasonic in distilled water or ethanol solution; the dropwise amount is controlled so that the loading amount of noble metal active component on the carbon paper is 0.27 mg / cm 2 . After drying at room temperature, the carbon paper loaded with diatomite composite catalyst material is obtained by Joule heating method (20V, 5A, 0.03s pulse current conduction).

[0099] Example 4

[0100] The diatomite composite catalytic material provided by the embodiment comprises 1 g of modified diatomite carrier and 0.0002 mol of active component Rh.

[0101] The preparation method is as follows:

[0102] S1, diatomite modification.

[0103] First step: prepare a 3 mol / L hydrochloric acid solution, and weigh the crushed diatomite ore into the above acid solution, and stir at 100°C for 1 h.

[0104] Second step: remove the solution by natural deposition of the solid-liquid mixture obtained in the first step, and centrifugally wash with distilled water for 3 times, and adjust the pH value of the suspension to 9.5 by dropwise adding a 2 mol / L sodium hydroxide solution.

[0105] Third step: after the solid-liquid mixture obtained in the second step is fully dispersed, it is sieved through 500 mesh, 1000 mesh, 1600 mesh and 2000 mesh sieves in sequence, and the sieve product on the 1600 mesh sieve is placed into an oven for drying, to obtain a large amount of single diatomite structure carrier with a length of 8-15 μm, for standby use.

[0106] S2, loading of noble metal active component.

[0107] First step: prepare a 0.005 mol / L rhodium nitrate solution and a 0.02 mol / L sodium citrate solution.

[0108] Second step: take 40 ml of the rhodium nitrate solution, 1 g of the modified carrier and 20 ml of distilled water solution into a 100 ml beaker, ultrasonically treat for 10 min, and then stir at room temperature for 30 min.

[0109] Third step: transfer the above solution into a stirring and heating reaction kettle, keep the stirring speed at 900 rpm, slowly drop 20 ml of the sodium citrate solution into the above mixture, close the reaction kettle, heat to 150°C and react for 5 h.

[0110] In the hydrothermal reaction system, the mass ratio of noble metal element: modified diatomite: water: sodium citrate is 2.05: 100: 8: 10.3.

[0111] Fourth step: filter the mixture in the reaction kettle, wash with distilled water and ethanol for several times respectively, and dry the obtained solid in a 60°C oven for 6 h, to obtain a catalyst semi-product.

[0112] S3, electrode preparation.

[0113] The synthesized catalyst semi-finished product is slightly ground into powder, 10 mg of which is ultrasonically dispersed with 20 μl of distilled water, 60 μl of an ethanol solution and 20 μl of a phenol solution for 2 h, and then 10 μl of the mixture is added dropwise to one side of the surface of a 0.7 cm*0.7 cm hydrophobic carbon paper; the amount of dropwise addition is controlled so that the loading amount of the noble metal active component on the carbon paper is 0.01 mg / cm 2 . Wait for room temperature drying to obtain the carbon paper loaded with the diatomite composite catalytic material.

[0114] Example 5

[0115] This example provides a diatomite composite catalytic material for electrochemical conversion of carbon dioxide into carbon monoxide, which comprises 1 g of a modified diatomite carrier and 0.0002 mol of an active component Ag.

[0116] The preparation method thereof is as follows:

[0117] S1, modification of diatomite.

[0118] First step: prepare a 2 mol / L citric acid solution, and weigh the crushed diatomite raw ore into the above acid solution, and stir at 80°C for 2 h.

[0119] Second step: remove the solution by natural deposition of the solid-liquid mixture obtained in the first step, and centrifugally wash with distilled water for 3 times, and adjust the pH value of the suspension to 9 by dropwise addition of a 2 mol / L sodium hydroxide solution.

[0120] Third step: after the solid-liquid mixture obtained in the second step is fully dispersed, it is sieved through 500 mesh, 1000 mesh, 1600 mesh and 2000 mesh sieves in sequence, and the sieve product on the 1600 mesh sieve is placed into an oven for drying to obtain a large amount of single diatomite carrier with a structure length of 8-15 μm, which is ready for use.

[0121] S2, loading of a noble metal active component.

[0122] First step: prepare a 0.005 mol / L silver nitrate solution and a 0.04 mol / L sodium citrate solution.

[0123] Second step: transfer 40 ml of the silver nitrate solution, 1 g of the modified carrier and 20 ml of a distilled water solution into a 100 ml beaker, ultrasonically treat for 10 min, and then stir at room temperature for 30 min.

[0124] Third step: transfer the above solution into a stirring and heating reaction kettle, keep the stirring speed at 700 rpm, slowly drop 20 ml of the sodium citrate solution into the above mixture, close the reaction kettle, heat to 140°C and react for 4 h.

[0125] In the hydrothermal reaction system, the mass ratio of noble metal element: modified diatomite: water: sodium citrate is 2.16: 100: 8: 20.6;

[0126] Fourth step: the mixture in the reaction kettle is suction filtered, washed with distilled water and ethanol several times respectively, and the obtained solid is placed in a 60℃ oven for drying for 5h to obtain a catalyst semi-finished product.

[0127] S3, electrode preparation.

[0128] The synthesized catalyst semi-finished product is slightly ground into powder, and is dispersed on one side surface of a hydrophobic carbon paper through ultrasonic dispersion in a distilled water or ethanol solution; the dropwise addition amount is controlled so that the loading amount of the noble metal active component on the carbon paper is 0.13mg / cm 2 After drying at room temperature, calcination is performed through the Joule heat method (30V, 8A, 0.03s pulse current conduction once), to obtain a carbon paper loaded with diatomite composite catalytic material.

[0129] Example 6

[0130] The example provides a diatomite composite catalytic material for electrochemical conversion of carbon dioxide into carbon monoxide, comprising 1g of modified diatomite carrier and 0.001mol of active component Ag.

[0131] The preparation method is as follows:

[0132] S1, diatomite modification.

[0133] First step: prepare a 3mol / L nitric acid solution, and weigh the crushed diatomite raw ore in the above acid solution and stir at 80℃ for 1h.

[0134] Second step: remove the solution by natural deposition of the solid-liquid mixture obtained in the first step, and centrifugally wash with distilled water for 3 times, and add 2mol / L sodium hydroxide solution to the suspension to adjust the pH value to 9.

[0135] Third step: after the solid-liquid mixture obtained in the second step is fully dispersed, it is sieved through 500 mesh, 1000 mesh, 1600 mesh and 2000 mesh sieves in sequence, and the sieve product on the 1600 mesh sieve is placed in an oven for drying, to obtain a large amount of single diatomite structure carrier with a length of 8-15μm, for standby use.

[0136] S2, loading of noble metal active component.

[0137] First step: prepare a 0.025mol / L silver nitrate solution and a 0.2mol / L sodium citrate solution.

[0138] Second step: 40 ml of silver nitrate solution, 1 g of modified carrier and 20 ml of distilled water solution were transferred into a 100 ml beaker, and then ultrasonic treatment was performed for 10 min, and stirring was performed at room temperature for 40 min.

[0139] Third step: the above solution was transferred into a stirring and heating reaction kettle, the stirring speed was kept at 900 rpm, 20 ml of sodium citrate solution was slowly added into the above mixture, the reaction kettle was closed, heated to 140℃ and reacted for 3 h.

[0140] In the hydrothermal reaction system, the mass ratio of noble metal element: modified diatomite: water: sodium citrate was 10.8: 100: 8: 103;

[0141] Fourth step: the mixture in the reaction kettle was filtered, washed with distilled water and ethanol several times, and the obtained solid was placed in a 60℃ oven for drying for 6 h to obtain a catalyst semi-finished product.

[0142] S3, electrode preparation.

[0143] The synthesized catalyst semi-finished product was slightly ground into powder, which was dispersed on one side surface of a hydrophobic carbon paper through a distilled water or ethanol solution; the dropwise addition amount was controlled so that the loading amount of noble metal active component on the carbon paper was 0.09 mg / cm 2 After drying at room temperature, calcination was performed by Joule heat method (60V, 10A, 0.01s pulse current conduction), and a carbon paper loaded with diatomite composite catalyst material was obtained.

[0144] Example 7

[0145] The example provides a diatomite composite catalyst material for electrochemical conversion of carbon dioxide into carbon monoxide, which comprises 1 g of modified diatomite carrier and 0.0002 mol of active component Ag.

[0146] The preparation method is as follows:

[0147] S1, diatomite modification.

[0148] First step: a 2 mol / L sulfuric acid solution was prepared, and the crushed diatomite raw ore was weighed and transferred into the above acid solution, and stirring was performed at 60℃ for 2 h.

[0149] Second step: the solid-liquid mixture obtained in the first step was naturally deposited to remove the solution, and distilled water was mixed and centrifuged for washing 3 times, and 2 mol / L of sodium hydroxide solution was added dropwise to adjust the pH value to 9.

[0150] Step 3: After fully dispersing the solid-liquid mixture obtained in Step 2, sieve it sequentially through 500 mesh, 1000 mesh, 1600 mesh, and 2000 mesh screens. Select the material from the 1600 mesh screen and dry it in an oven to obtain a large number of carriers with individual diatomaceous earth structures with a length of 8 to 15 μm for later use.

[0151] S2, loading of noble metal active components.

[0152] Step 1: Prepare a 0.005 mol / L silver nitrate solution and a 0.04 mol / L sodium citrate solution.

[0153] Step 2: Transfer 40 ml of silver nitrate solution, 1 g of modified carrier and 20 ml of distilled water into a 100 ml beaker, sonicate for 10 min and then stir at room temperature for 40 min.

[0154] Step 3: Transfer the above solution to a stirred and heated reactor, maintain a stirring speed of 700 rpm, slowly add 20 ml of sodium citrate solution to the above mixture, seal the reactor, and heat to 140°C for 3 hours.

[0155] In the hydrothermal reaction system, the mass ratio of precious metal element: modified diatomaceous earth: water: sodium citrate is 2.16:100:8:20.6;

[0156] Step 4: Filter the mixture in the reactor, wash it several times with distilled water and ethanol respectively, and dry the resulting solid in an oven at 60°C for 7 hours to obtain a catalyst semi-finished product.

[0157] S3, Electrode preparation.

[0158] The synthesized catalyst semi-finished product was lightly ground into powder and dispersed on one side of a hydrophobic carbon paper using distilled water or ethanol solution; the amount added was controlled to ensure that the loading of the noble metal active component on the carbon paper was 0.21 mg / cm³. 2 After drying at room temperature, the carbon paper loaded with diatomaceous earth composite catalyst is obtained by calcination using the Joule heating method (20V, 5A, 0.05s pulse current conduction).

[0159] Part Three: Comparative Cases Different from the Invention

[0160] Comparative Example 1

[0161] Refer to "H3PW 12 O 40The preparation, characterization and catalytic synthesis of n-butyl acetate of acid-modified diatomite catalyst (DOI: 10.16085 / j.issn.1000-6613.2019-0813) are described. The diatomite is immersed in sulfuric acid of a certain concentration and treated by high-temperature calcination to obtain the corresponding acid-modified diatomite. Compared with the modification method in Example 2, the specific surface area of the carrier is smaller, the pore volume and average pore size are larger, and under the same loading conditions, it is difficult to support the growth of nanoscale noble metals, and the electrocatalytic performance is not ideal.

[0162] Comparative Example 2

[0163] In Comparative Example 2, the preparation process of the diatomite carrier is the same as that of Example 2, except that the catalyst loading operation uses copper nitrate solution instead of silver nitrate for synthesis and preparation, and finally the copper grows in dendritic form on the diatomite, which is difficult to disperse. Under the same test conditions, the yield and conversion efficiency of CO and H2 in the electrocatalytic reduction of CO2 in aqueous solution are not ideal.

[0164] Comparative Example 3

[0165] A commercially available analytical pure diatomite (Tianjin Damao Chemical Reagent Factory, No. 3714) is purchased and subjected to the same catalyst loading operation as in Example 6. The purchased diatomite has a more disc-like morphology, more broken components, a smaller specific surface area than the diatomite used in the example, and a higher purity. The prepared electrode loaded with noble metal components has a larger size, and the catalytic performance under the same test conditions is not ideal.

[0166] Comparative Example 4

[0167] In Comparative Example 4, the other material synthesis steps are the same as in Example 6, and in the activation of the composite catalytic material, the power-on time is extended to 0.2 s. The prepared electrode sheet shows that the loaded metal size is larger and the distribution is not uniform, which leads to unsatisfactory catalytic performance under the same test conditions.

[0168] Fourth part: catalytic performance test and data analysis

[0169] The test platform is built in the following manner to test the conversion rate of CO in the electrocatalytic reduction of CO2.

[0170] Under normal pressure, the carbon paper loaded with diatomite composite catalytic material is fixed as a working electrode with a glassy carbon electrode clamp, and an Ag / AgCl reference electrode, a 0.5 cm 2 The platinum sheet counter electrode is used for three-electrode catalytic performance test, the electrolyte is 0.5 mol / L KHCO3 solution, the CO2 flow rate is 22 sccm, the overpotential and current density of the catalyst are obtained by the electrochemical workstation, and the CO yield is analyzed by the chromatograph.

[0171] Test results of each example:

[0172] Example 1: Under the conditions of normal temperature and pressure, and potential of -1.6V, the current density of the catalyst was 10.8 mA / cm 2 , and the conversion rate of CO was 15.2%. The catalytic effect was stable after 480h of testing.

[0173] Example 2: Under the conditions of normal temperature and pressure, and potential of -1.6V, the current density of the catalyst was 11.6 mA / cm 2 , and the conversion rate of CO was 16.8%. The catalytic effect was stable after 480h of testing.

[0174] Example 3: Under the conditions of normal temperature and pressure, and potential of -1.6V, the current density of the catalyst was 12.5 mA / cm 2 , and the conversion rate of CO was 15.0%. The catalytic effect was stable after 480h of testing.

[0175] Example 4: Under the conditions of normal temperature and pressure, and potential of -1.6V, the current density of the catalyst was 11.0 mA / cm 2 , and the conversion rate of CO was 14.5%. The catalytic effect was stable after 480h of testing.

[0176] Example 5: Under the conditions of normal temperature and pressure, and potential of -1.6V, the current density of the catalyst was 15.2 mA / cm 2 , and the conversion rate of CO was 25.2%. The catalytic effect was stable after 480h of testing.

[0177] Example 6: Under the conditions of normal temperature and pressure, and potential of -1.6V, the current density of the catalyst was 14.8 mA / cm 2 , and the conversion rate of CO was 21.0%. The catalytic effect was stable after 480h of testing.

[0178] Example 7: Under the conditions of normal temperature and pressure, and potential of -1.6V, the current density of the catalyst was 13.2 mA / cm 2 , and the conversion rate of CO was 15.6%. The catalytic effect was stable after 480h of testing.

[0179] Comparative Example 1: Under the conditions of normal temperature and pressure, and potential of -1.6V, the current density of the catalyst was 9.5 mA / cm 2 , and the conversion rate of CO was 6.4%. The catalytic effect was stable after 480h of testing.

[0180] Comparative Example 2: Under the conditions of normal temperature and pressure, and potential of -1.6V, the current density of the catalyst was 10.3 mA / cm 2 , and the conversion rate of CO was 3.8%. The catalytic effect decreased seriously after 480h of testing.

[0181] Comparative Example 3: under the conditions of normal temperature and pressure, and potential of -1.6V, the current density of the catalyst is 7.2mA / cm 2 , and the conversion rate of CO is 4.4%. The catalytic effect is stable after 480h of testing.

[0182] Comparative Example 4: under the conditions of normal temperature and pressure, and potential of -1.6V, the current density of the catalyst is 11.4mA / cm 2 , and the conversion rate of CO is 5.2%. The catalytic effect is stable after 480h of testing.

[0183] The final results are shown in the following table:

[0184]

[0185] From the test data of the examples and comparative examples, the following conclusions can be obtained:

[0186] 1. The diatomite composite catalyst product of the present application realizes effective electrocatalytic reduction of CO2 to CO;

[0187] 2. The diatomite raw material and noble metal component selected in the examples have a 2-4 times higher yield of target product than the comparative examples, and have good stability;

[0188] 3. The present application realizes optimization of the catalyst material in terms of important indicators such as yield of target product, catalytic activity, and working stability, by adjusting the preparation and activation process parameters. For example, the use of Joule heating method to prepare the electrode effectively removes the organic components of diatomite, further expanding the pore structure of the material, and the sintering of the catalyst and conductive carbon paper also enhances the electrical conductivity of the electrode, improving the catalytic activity.

[0189] 4. The present application can adjust the catalyst morphology and the ratio of the final reduction product by adjusting the material synthesis components and process parameters, which is sufficient to meet the needs of different working environments.

[0190] 5. The electrode sheet produced by the present application has simple operation process, short time, and low cost, and is suitable for industrial scale production.

[0191] Obviously, the described examples are only part of the embodiments of the present application, not all. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without creative labor belong to the scope of protection of the present application.

Claims

1. A method for preparing a diatomaceous earth composite catalytic material, characterized in that, Includes the following steps: (1) Acid leaching modification treatment of diatomaceous earth The crushed diatomaceous earth ore is added to an acid solution and subjected to acid leaching while stirring. After natural sedimentation, the precipitate is collected, washed by centrifugation with distilled water, mixed with alkaline solution, and the pH value is adjusted to weakly alkaline. The resulting mixture is then fully dispersed, sieved, and dried to obtain modified diatomaceous earth. (2) Loading of noble metal active components A precious metal nitrate aqueous solution, modified diatomaceous earth, and an appropriate amount of distilled water were mixed at room temperature and ultrasonically treated. The mixture was then transferred to a reaction vessel, and sodium citrate solution was added under stirring. The reaction vessel was then sealed for hydrothermal reaction. In the hydrothermal reaction system, the mass ratio of precious metal element: modified diatomaceous earth: water: sodium citrate was 0.4–10.8:100:8:1.03–103. After the reaction was completed, the reaction product was filtered, washed, and the solid was dried to obtain a catalyst semi-finished product. (3) Activation of composite catalytic materials Activate the composite catalytic material using any of the following methods: (3.1) The catalyst semi-finished product is ground into powder and added to a mixture of distilled water-ethanol-phenol for ultrasonic dispersion; the dispersion is dropped onto one side of the surface of hydrophobic carbon paper and dried at room temperature to obtain carbon paper used as an electrode, on which diatomaceous earth composite catalyst material is loaded. or, (3.2) Grind the catalyst semi-finished product into powder and add it to distilled water or ethanol solution for dispersion; take the dispersion and drop it onto one side of the surface of hydrophobic carbon paper, dry it at room temperature, and then calcine it using the Joule heating method to obtain carbon paper that can be used as an electrode. Diatomaceous earth composite catalyst material is loaded on the carbon paper.

2. The method according to claim 1, characterized in that, In step (1), the acid solution is a hydrochloric acid solution, nitric acid solution, sulfuric acid solution or citric acid solution with a concentration of 1 to 3 mol / L, and the temperature of the acid leaching treatment is 20 to 100°C and the time is 1 to 3 hours; the alkaline solution is a potassium hydroxide solution with a concentration of 2 mol / L.

3. The method according to claim 1, characterized in that, In step (1), the centrifugation washing is performed 3 times, and the pH value is adjusted to 9-10; the monomer structure length of the modified diatomite after sieving and drying is 8-15 μm.

4. The method according to claim 1, characterized in that, In step (2), the precious metal element is at least one of palladium, silver, ruthenium or rhodium; the concentration of the precious metal nitrate aqueous solution is 0.001 to 0.025 mol / L, and the concentration of the sodium citrate solution is 0.002 to 0.2 mol / L.

5. The method according to claim 1, characterized in that, In step (2), when mixing the precious metal nitrate aqueous solution, modified diatomaceous earth and distilled water, the mixture is first ultrasonically treated for 10 minutes, and then stirred at room temperature for 20 to 40 minutes; when adding sodium citrate solution, the stirring speed is maintained at 500 to 900 rpm; the hydrothermal reaction temperature is 130 to 150°C and the time is 3 to 5 hours.

6. The method according to claim 1, characterized in that, In step (2), the reaction product is filtered and washed several times with distilled water and ethanol, and the resulting solid is dried in an oven at 60°C for 5-7 hours.

7. The method according to claim 1, characterized in that, In step (3), the ultrasonic dispersion time is 2 hours.

8. The method according to claim 1, characterized in that, In step (3), the amount of dispersion added is controlled so that the loading of the noble metal active component on the carbon paper is 0.01–0.27 mg / cm³. 2 .

9. The method according to claim 1, characterized in that, In step (3.2), during the calcination process using the Joule heating method, the parameters are controlled as follows: 20-60V, 5-10A, 0.01-0.05s, and a single pulse current is turned on.

10. The method for applying the carbon paper loaded with diatomaceous earth composite catalyst material prepared by the method described in claim 1 in the electrocatalytic reduction of CO2, characterized in that, The carbon paper is used as the working electrode, together with the Ag / AgCl reference electrode and the platinum sheet as the counter electrode to form a three-electrode system; KHCO3 solution is used as the electrolyte, and the catalyst overpotential and current density are obtained through an electrochemical workstation, thereby reducing CO2 gas to CO.

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