Doped large-particle hydroxyl cobalt oxide as well as preparation method and application thereof

Abstract

The invention discloses doped large-particle hydroxyl cobalt oxide as well as a preparation method and application thereof. The preparation method of the doped large-particle cobalt oxyhydroxide comprises the following steps: dissolving cobalt salt and doped metal salt in water to prepare a mixed salt solution; under the stirring condition, the mixed salt solution and the precipitator solution are added into a reactor in a parallel flow mode, the pH of a reaction system is controlled to be 8.0-11.0, the temperature is controlled to be 40-70 DEG C, aging is carried out after charging is completed, a co-precipitation reaction is carried out, and doped precursor slurry is obtained; and adding an oxidizing agent into the doped precursor slurry, carrying out oxidation reaction at 60-95 DEG C, and filtering, washing and drying the product after the reaction is finished. The hydroxyl cobalt oxide prepared by the method is large particles of 10-50 microns, has good fluidity, is easy to be filled in a fixed bed, can be directly used for a flowing type electrolytic tank, and solves the engineering application problem of nano powder.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic materials technology, and particularly relates to a doped large-particle cobalt hydroxyoxide, its preparation method, and its application. Background Technology

[0002] Cobalt hydroxyoxide (CoOOH) is an important functional material that has attracted widespread attention in the fields of energy, catalysis and environment due to its excellent electrochemical activity and stability. In particular, its oxidase-like activity and electrocatalytic oxidation performance have shown great potential in reactions such as the oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) and alcohol oxidation.

[0003] However, most current research focuses on nanoscale CoOOH materials (such as nanosheets, nanowires, quantum dots, etc.). Although nanomaterials have a large specific surface area and many exposed active sites, they also have obvious inherent defects: (1) easy agglomeration: the van der Waals forces between nanoparticles are strong, and agglomeration is very easy to occur during preparation, storage and use, resulting in a decrease in actual specific surface area and activity decay; (2) poor flowability: in slurry systems, nanomaterials have high viscosity and it is difficult to increase the solid content, which is not conducive to large-scale slurry coating or slurry transportation; (3) application limitations: in fixed bed reactors or flowing electrolytic cells, the use of nanoparticles will cause a sharp increase in system pressure drop, or even block the flow channel, making it difficult to achieve industrial continuous operation.

[0004] Furthermore, the conductivity of pure-phase CoOOH still needs improvement, and its intrinsic catalytic activity limits its further applications. Although some studies have improved its electronic structure through doping (such as Cu doping), these studies are still limited to the nanoscale and have failed to solve the aforementioned macroscopic application bottlenecks.

[0005] Therefore, developing a cobalt hydroxyl oxide material that combines high catalytic activity, good conductivity, and suitable macroscopic particle size has become the key to promoting its industrial application. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a doped large-particle cobalt hydroxyl oxide, its preparation method, and its applications. The preparation method described in this invention is simple, reproducible, and easily scalable for mass production. The resulting product exhibits both high catalytic activity and excellent engineering application performance.

[0007] The objective of this invention is achieved through the following technical solution: A method for preparing doped large-particle cobalt hydroxyoxide includes the following steps: A mixed salt solution was prepared by dissolving cobalt salt and doped metal salt in water; Under stirring conditions, the mixed salt solution and the precipitant solution are added to the reactor in parallel flow. The pH of the reaction system is controlled at 8.0~11.0 and the temperature at 40~70℃. After the addition is completed, the mixture is aged to carry out a co-precipitation reaction to obtain a doped precursor slurry. An oxidant is added to the doped precursor slurry, and an oxidation reaction is carried out at 60~95℃. After the reaction is completed, the product is filtered, washed and dried to obtain the doped large-particle cobalt hydroxyl oxide.

[0008] In this invention, the doped large-particle cobalt hydroxyl oxide is a regular spherical or near-spherical secondary particle, which is self-assembled from primary nanosheets / nanoneedles. The overall particle size D50 is 10~50μm and the specific surface area is 20~150 m² / g.

[0009] Preferably, the molar ratio of Co in the cobalt salt to the metal in the doped metal salt is 10~100:1.

[0010] Preferably, the doped metal salt is at least one selected from Cu salt, Fe salt, Ni salt, La salt, and Mn salt.

[0011] Preferably, the concentration of cobalt salt in the mixed salt solution is 0.5~3.5 mol / L.

[0012] Preferably, the mixed salt solution and the precipitant solution are added to the reactor in parallel flow at a stirring speed of 200~600 r / min.

[0013] Preferably, the concentration of the precipitant solution is 10-30 wt%; the mass ratio of the precipitant solution to the mixed salt solution is 1:1-2.

[0014] Preferably, the precipitant is at least one selected from ammonium bicarbonate, sodium carbonate, and sodium hydroxide.

[0015] Preferably, the coprecipitation reaction takes 1 to 4 hours.

[0016] Preferably, the feeding time is 0.5 to 2 hours.

[0017] Preferably, the mass ratio of the oxidant to the cobalt salt is 0.15 to 0.3:1.

[0018] Preferably, the oxidation reaction takes 1 to 12 hours.

[0019] Preferably, the oxidant is at least one selected from ammonium persulfate, potassium persulfate, hydrogen peroxide, and sodium hypochlorite.

[0020] The doped large-particle cobalt hydroxyoxide prepared by the above-described method is a doped large-particle cobalt hydroxyoxide.

[0021] The above-mentioned doped large-particle cobalt hydroxyoxide is used as an electrocatalyst, a surface coating agent for lithium-ion battery cathode materials, and a heterogeneous catalyst in oxidation reactions.

[0022] Specifically, doped large-particle cobalt hydroxyoxide is used as an electrocatalyst to catalyze the electrochemical oxidation of 5-hydroxymethylfurfural (HMF) to prepare 2,5-furandicarboxylic acid (FDCA); as an electrocatalyst, it is used to catalyze the electrochemical oxidation reactions of small organic molecules such as alcohols and aldehydes; as a surface coating agent for lithium-ion battery cathode materials (such as NCM and NCA) to suppress interfacial side reactions; and as a heterogeneous catalyst in advanced oxidation processes to degrade organic pollutants.

[0023] Compared with the prior art, the beneficial effects of the present invention include: (1) Combination of macroscopic particle size and microscopic activity: The cobalt hydroxyl oxide prepared by this invention has large particle size of 10~50μm, good flowability, and is easy to fill a fixed bed. It can be directly used in a flow electrolytic cell, solving the engineering application problem of nanopowders. At the same time, its secondary particles are composed of nano-primary structures, retaining high specific surface area and abundant active sites.

[0024] (2) Doping modification enhances intrinsic activity: By introducing doped metal elements, the electronic structure of CoOOH is effectively regulated, the charge transport impedance is reduced, and the conductivity and intrinsic catalytic activity of the material are improved.

[0025] (3) Simple process and easy to scale up: This method adopts mature liquid phase coprecipitation and oxidation aging technology, with a short process flow, easy parameter control, and good reproducibility, making it very suitable for large-scale production at the hundred-kilogram level or even the ton level.

[0026] (4) Broad application prospects: This material has important application value in fields such as biomass conversion, energy storage materials and environmental catalysis. In particular, it provides a high-performance and low-cost catalyst solution for the upgrading of HMF to prepare high-value chemicals. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] Example 1 A method for preparing doped large-particle cobalt hydroxyl oxide, the specific steps of which are as follows: (1) Dissolve 100g of cobalt nitrate hexahydrate and 1.29g of copper nitrate trihydrate (Cu / Co molar ratio = 1:50) in 500mL of deionized water to prepare solution A; Dissolve 80g of ammonium bicarbonate in 500mL of deionized water to prepare solution B; 100 mL of deionized water was added to the reactor as a base solution, heated to 50 °C, and the stirring speed was set to 400 rpm. Solutions A and B were added to the reactor in parallel using a constant flow pump, and the feeding time was controlled to be 1 h. The pH of the system was maintained at 9.5 by adding ammonia dropwise. After the feeding was completed, the mixture was aged for another 1 h to carry out a co-precipitation reaction, and a pink precursor slurry was obtained. The precursor particles were measured to have a D50 of 12.385 μm by a laser particle size analyzer. (2) Add 20g of ammonium persulfate to the precursor slurry, heat to 85℃, react for 6h, and the slurry color gradually turns brownish-black; after the reaction is completed, filter the product, wash it three times with deionized water and ethanol, and dry it in a vacuum drying oven at 80℃ for 12h to obtain the final product, namely Cu-doped CoOOH.

[0029] According to the Zhuhai Omec laser particle size analyzer, the D50 of Cu-doped CoOOH is 15.507 μm; according to the specific surface area analyzer, the specific surface area is 70.682 m² / g.

[0030] Example 2 A method for preparing doped large-particle cobalt hydroxyl oxide, the specific steps of which are as follows: (1) Dissolve 100g of cobalt nitrate hexahydrate and 2.78g of ferric nitrate nonahydrate (Fe / Co molar ratio = 1:50) in 500mL of deionized water to prepare solution A; Dissolve 80g of ammonium bicarbonate in 500mL of deionized water to prepare solution B; 100 mL of deionized water was added to the reactor as a base solution, heated to 55 °C, and the stirring speed was set to 450 rpm. Solutions A and B were added to the reactor in parallel using a constant flow pump, and the feeding time was controlled to be 1.5 h. The pH of the system was maintained at 10.0 by adding ammonia dropwise. After the feeding was completed, the mixture was aged for another 1 h to carry out a co-precipitation reaction, and a pink precursor slurry was obtained. The precursor particles were measured to have a D50 of 16.052 μm by a laser particle size analyzer. (2) Add 22g of potassium persulfate (the mass ratio of potassium persulfate to cobalt salt is 0.22:1) to the precursor slurry, heat to 80℃, react for 5h, and the slurry color gradually turns brownish-black; after the reaction is completed, filter the product, wash it three times with deionized water and ethanol, and dry it in a vacuum drying oven at 80℃ for 12h to obtain the final product, namely Fe-doped CoOOH.

[0031] According to the Zhuhai Omec laser particle size analyzer, the D50 of Fe-doped CoOOH is 18.175 μm; according to the specific surface area analyzer, the specific surface area is 65.320 m² / g.

[0032] Example 3 A method for preparing doped large-particle cobalt hydroxyl oxide, the specific steps of which are as follows: (1) Dissolve 100g of cobalt nitrate hexahydrate and 2g of nickel nitrate hexahydrate (Ni / Co molar ratio = 1:50) in 500mL of deionized water to prepare solution A; Dissolve 90g of sodium carbonate in 500mL of deionized water to prepare solution B; 100 mL of deionized water was added to the reactor as a base solution, heated to 60 °C, and the stirring speed was set to 500 rpm. Solutions A and B were added to the reactor in parallel using a constant flow pump, with the feeding time controlled at 1 h. The pH of the system was maintained at 9.0 by adding ammonia dropwise. After the feeding was completed, the mixture was aged for 1.5 h for co-precipitation reaction to obtain a pink precursor slurry. The precursor particles were measured to have a D50 of 12.580 μm by a laser particle size analyzer. (2) Add 25g of hydrogen peroxide (the mass ratio of hydrogen peroxide to cobalt salt is 0.25:1, and the concentration of hydrogen peroxide is 30 wt%) to the precursor slurry, heat to 75℃, react for 4h, and the slurry color gradually turns brownish-black; after the reaction is completed, filter the product, wash it three times with deionized water and ethanol, and dry it in a vacuum drying oven at 80℃ for 12h to obtain the final product, namely Ni-doped CoOOH.

[0033] According to the Zhuhai Omec laser particle size analyzer, the D50 of Ni-doped CoOOH is 16.702 μm; according to the specific surface area analyzer, the specific surface area is 82.105 m² / g.

[0034] Comparative Example 1 Comparative Example 1 provides a method for preparing cobalt hydroxyoxide. Compared with Example 1, the only difference is that no doping metal is added, and the other steps are completely the same as those in Example 1.

[0035] Comparative Example 2 The liquid-phase coprecipitation method, a common technique in existing technologies, is used, in which metal salts, precipitants, and oxidants are simultaneously added to the reaction system. The specific steps are as follows: (1) Dissolve 100g of cobalt nitrate hexahydrate and 1.29g of copper nitrate trihydrate (Cu / Co molar ratio = 1:50) in 500mL of deionized water to prepare a mixed metal salt solution; Dissolve 80g of ammonium bicarbonate and 20g of ammonium persulfate together in 500mL of deionized water to prepare a mixed solution containing a precipitant and an oxidant. (2) 100 mL of deionized water was added to the reactor as a base liquid and heated to 50 °C. Under the condition of vigorous stirring with a stirring speed of 800 rpm, the mixed metal salt solution and the precipitant-oxidant mixed solution were added to the reactor in parallel by two constant flow pumps. The feeding time was controlled to be 1 h. The pH of the system was maintained at 9.5 by adding ammonia dropwise. After the feeding was completed, the reaction was continued at 50 °C for 1 h. At this time, the slurry had changed from pink to brownish-black.

[0036] (3) After the reaction is complete, the product is filtered, washed three times with deionized water and ethanol, and dried in a vacuum drying oven at 80°C for 12 hours to obtain the final product. Nanosheet Cu-doped CoOOH with a particle size of 100~500nm is prepared.

[0037] Comparative Example 3 The effect of simultaneous addition of precipitant and oxidant on the product The only difference between Comparative Example 3 and Example 1 is that Solution A (mixed metal salt solution), Solution B (precipitant solution), and oxidant (ammonium persulfate) were added to the reactor simultaneously in parallel, while other conditions remained unchanged.

[0038] The product prepared in Comparative Example 3 was an irregular particle with D50 = 5.025 μm and a specific surface area of ​​130.682 m² / g. The particle morphology was uneven and there was a large amount of agglomeration.

[0039] Comparative Example 4 Effect of pH on the product The only difference between Comparative Example 4 and Example 1 is that the pH in step (1) is controlled at 7.0 (below the scope of the present invention), while other conditions remain unchanged.

[0040] Comparative Example 4 showed incomplete precipitation of the precursor slurry. After oxidation and aging, the product had small particle size (D50=8.538μm) and poor sphericity, with a specific surface area of ​​110.906m² / g.

[0041] Application Experiment: Electrocatalytic Oxidation of HMF 0.1 g of doped large-particle cobalt hydroxyl oxide prepared in Example 1 of this invention was added as a catalyst to the anode chamber of an H-type electrolytic cell. Then, 1.0 g of HMF dissolved in 100 mL of 0.1 M KOH solution was injected into the electrolytic cell, and electrolysis was carried out at a constant potential of 1.45 V (vs. RHE). After 2 h of electrolysis, the HMF conversion rate was >99%, the FDCA yield reached 95%, and the Faraday efficiency was 92%. After the reaction, the catalyst could be easily recovered by sedimentation or filtration; after five consecutive cycles, the FDCA yield remained above 90%.

[0042] In comparison, the FDCA yield was 85% when using cobalt hydroxyoxide prepared in Comparative Example 1; while the Cu-doped CoOOH prepared in Comparative Example 2 showed comparable catalytic activity to that of Example 1 in the initial reaction, it was easily lost during recycling and reuse due to its nanoparticles, and was difficult to separate effectively, thus it could not be used in a flow electrolysis system.

[0043] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing doped large-particle cobalt hydroxyl oxide, characterized in that, Includes the following steps: A mixed salt solution was prepared by dissolving cobalt salt and doped metal salt in water; Under stirring conditions, the mixed salt solution and the precipitant solution are added to the reactor in parallel flow. The pH of the reaction system is controlled at 8.0~11.0 and the temperature at 40~70℃. After the addition is completed, the mixture is aged to carry out a co-precipitation reaction to obtain a doped precursor slurry. An oxidant is added to the doped precursor slurry, and an oxidation reaction is carried out at 60~95℃. After the reaction is completed, the product is filtered, washed and dried to obtain the doped large-particle cobalt hydroxyl oxide.

2. The method for preparing doped large-particle cobalt hydroxyl oxide according to claim 1, characterized in that, The molar ratio of Co in the cobalt salt to the metal in the doped metal salt is 10~100:

1.

3. The method for preparing doped large-particle cobalt hydroxyl oxide according to claim 1, characterized in that, In the mixed salt solution, the concentration of cobalt salt is 0.5~3.5 mol / L.

4. The method for preparing doped large-particle cobalt hydroxyl oxide according to claim 1, characterized in that, The mixed salt solution and the precipitant solution are added to the reactor in parallel flow at a stirring speed of 200~600 r / min.

5. The method for preparing doped large-particle cobalt hydroxyl oxide according to claim 1, characterized in that, The concentration of the precipitant solution is 10~30wt%; the mass ratio of the precipitant solution to the mixed salt solution is 1:1~2.

6. The method for preparing doped large-particle cobalt hydroxyl oxide according to claim 1, characterized in that, The coprecipitation reaction time is 1-4 hours; and / or The oxidation reaction takes 1-12 hours; and / or The feeding time is 0.5~2 hours.

7. The method for preparing doped large-particle cobalt hydroxyl oxide according to claim 1, characterized in that, The mass ratio of the oxidant to the cobalt salt is 0.15~0.3:

1.

8. The method for preparing doped large-particle cobalt hydroxyl oxide according to claim 1, characterized in that, The doped metal salt is at least one selected from Cu, Fe, Ni, La, and Mn salts; and / or The precipitant is at least one selected from ammonium bicarbonate, sodium carbonate, and sodium hydroxide; and / or The oxidant is at least one of ammonium persulfate, potassium persulfate, hydrogen peroxide, and sodium hypochlorite.

9. Doped large-particle cobalt hydroxyoxide prepared by the method according to any one of claims 1 to 8.

10. The application of the doped large-particle cobalt hydroxyoxide as described in claim 9 as an electrocatalyst, a surface coating agent for lithium-ion battery cathode materials, and a heterogeneous catalyst in oxidation reactions.