Preparation method and application of platinum modified defect cobalt oxide catalyst

Abstract

The invention relates to the technical field of preparation of electro-catalysis electrode materials, in particular to a preparation method and application of a platinum-modified defect cobalt oxide catalyst, firstly, cobalt salt and glycerin are evenly mixed, a defect cobalt oxide precursor is obtained through a hydrothermal method, then, the precursor is subjected to high-temperature calcination to obtain defect cobalt oxide, and finally, the platinum-modified defect cobalt oxide catalyst is obtained. The method comprises the following steps: uniformly mixing defect cobalt oxide and platinum salt, and carrying out hydrothermal treatment to obtain a Pt-Vco catalyst; the Pt-Vco catalyst is prepared through a three-step hydrothermal-calcination-hydrothermal method, and the preparation method is simple, convenient to operate and high in practicability; the obtained Pt-Vco catalyst has excellent activity, low initial potential and high stability, the performance of electrocatalytic oxidation of HMF is remarkably improved, and the market prospect is wide.

Description

Technical field:

[0001] The present invention relates to the technical field of electrocatalytic electrode material preparation, and in particular to a preparation method and application of a platinum-modified defective cobalt oxide catalyst. Background technology:

[0002] With the rapid consumption of fossil resources, the development of renewable resources has attracted widespread attention in countries around the world. The use of abundant renewable biomass resources to prepare bulk chemicals and fine chemicals to make up for the shortage of petroleum resources has become an important development direction in the future and is of great significance. 5-Hydroxymethylfurfural (HMF) plays an important bridging role between biomass and fossil resources, while the oxidation of 5-hydroxymethylfurfural (HMFOR) provides the possibility of simultaneously producing low-energy and high-value-added products. Among the selective oxidation products of HMF, 2,5-furandicarboxylic acid (FDCA) has attracted more attention due to its application in the production of polyethylene 2,5-furandicarboxylate (PEF). PEF is considered a potential substitute for petroleum-derived polyethylene terephthalate (PET). Therefore, HMFOR is of great significance to the industrial and scientific fields. It is crucial to deeply understand the catalytic mechanism of HMF electrooxidation and develop electrocatalysts with high catalytic performance.

[0003] Cobalt oxide (Co3O4), which is abundant on earth, is an alternative catalyst for HMFOR. As an abundant transition metal oxide, cobalt oxide (Co3O4) has the characteristics of direct oxidation and indirect oxidation, but poor performance in competitive oxygen evolution reaction (OER), and is considered to be a promising catalyst. However, its weak ability to enrich active molecules limits its further development.

[0004] Among the many strategies for optimizing catalytic performance, defect engineering can break symmetry and improve catalytic activity. However, current research mainly involves oxygen defects, and there is little research on the role of metal defects in biomass catalysis. Summary of the invention:

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing an efficient and stable platinum-modified defective cobalt oxide (Pt-Vco) catalyst and its application. Through a simple hydrothermal reaction, defective cobalt oxide (Vco) induces exogenous Pt δ+ Compared with the Co3O4 electrode, the Pt-Vco catalyst exhibits excellent electrocatalytic performance, which is manifested in higher FDCA yield, Faradaic efficiency and current density.

[0006] To achieve the above-mentioned object of the invention, the present invention provides a method for preparing a platinum-modified defective cobalt oxide catalyst, comprising the following steps:

[0007] (1) Preparing defective cobalt oxide: mixing cobalt salt and glycerol evenly, and synthesizing a defective cobalt oxide precursor cobalt glycerate (GlyCo) material by hydrothermal reaction; then using the GlyCo material as a defective cobalt oxide precursor, and calcining at high temperature to obtain defective cobalt oxide;

[0008] (2) Preparation of platinum-modified defective cobalt oxide: The obtained defective cobalt oxide and platinum salt are mixed and stirred, and then subjected to a hydrothermal reaction to obtain a platinum-modified defective cobalt oxide (Pt-Vco) catalyst.

[0009] The cobalt salt in step (1) is cobalt nitrate or cobalt acetate. The molar ratio of the cobalt salt to glycerol is 1:(70-100); the hydrothermal reaction temperature is 160-200°C and the time is 1-4 hours; the high-temperature calcination is carried out in an oxygen atmosphere at 200-400°C at a heating rate of 5°C / min for 1-4 hours.

[0010] The platinum salt in step (2) is platinum nitrate, platinum sulfate or chloroplatinic acid.

[0011] In the step (2), the hydrothermal reaction temperature is 100 to 150° C. and the reaction time is 1 to 4 hours.

[0012] The raw materials involved in the hydrothermal reaction in step (2) also include ethylene glycol. The molar ratio of defective cobalt oxide, ethylene glycol and platinum salt is (2-3): (500-10000): (0.3-0.9).

[0013] After the hydrothermal reaction in step (2), the solid product is collected by centrifugation or filtration and placed in an oven to dry at 60° C. for 8-12 hours.

[0014] The present invention also provides a platinum-modified defective cobalt oxide catalyst prepared by the method.

[0015] The present invention also provides the use of the platinum-modified defective cobalt oxide catalyst in the electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF), which can be used to promote the anode to obtain a high value-added oxidation product 2,5-furandicarboxylic acid.

[0016] The research and development idea of ​​the present invention is as follows: Since the enrichment and activation effect of Co3O4 on OH and HMF is weak, its further application is limited. Therefore, in order to further improve the electrocatalytic activity of Co3O4, the present invention utilizes the construction of metal defects and the modification of Pt at the defect sites to deeply optimize the surface electronic structure and coordination environment, thereby significantly improving the performance of 5-hydroxymethylfurfural oxidation.

[0017] Compared with the prior art, the Pt-Vco catalyst prepared by the present invention has the following advantages:

[0018] (1) The onset potential of Pt-Vco (1.14 V) is lower than that of pure Co3O4 (1.35 V), and the current density at 1.35 V is 19 times higher than that of Co3O4. This is due to the introduction of Pt at defect sites and the regulation of the electronic structure of heterogeneous components, which leads to reduced antibonding orbital electron filling and upward shift of the Co d band center, thus exhibiting excellent electrocatalytic performance.

[0019] (2) The number of direct catalytic sites of the catalyst of the present invention increases, the charge transfer is accelerated during the reaction, and the kinetic rate is faster.

[0020] (3) The catalyst of the present invention exhibits excellent stability in HMF oxidation.

[0021] (4) The catalyst preparation and synthesis method of the present invention is simple and has high commercial prospects.

[0022] In summary, the present invention prepares the Pt-Vco catalyst by a three-step hydrothermal-calcination-hydrothermal method, and the preparation method is simple, easy to operate, and highly practical; the obtained Pt-Vco catalyst has excellent activity, low starting potential and high stability, which significantly improves the performance of electrocatalytic oxidation of HMF and has broad market prospects. Description of the drawings:

[0023] Figure 1 This is the XRD diagram of the Pt-Vco catalyst of Example 1 of the present invention.

[0024] Figure 2 This is a SEM image of the Pt-Vco catalyst of Example 1 of the present invention.

[0025] Figure 3 This is the HRTEM image of the Pt-Vco catalyst of Example 1 of the present invention.

[0026] Figure 4 This is a HMFOR linear sweep voltammetry test diagram of the Pt-Vco catalyst of Example 1 of the present invention.

[0027] Figure 5 This is a diagram of FDCA yield and Faraday efficiency in six HMFOR cycles of the Pt-Vco catalyst of Example 1 according to the present invention. Specific implementation method:

[0028] The present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0029] Embodiment 1:

[0030] This embodiment relates to a method for preparing a platinum-modified defective cobalt oxide catalyst, and the steps are as follows:

[0031] (1) Preparation of GlyCo (cobalt glycerate)

[0032] 4 mmol of cobalt acetate and 0.4 mol of glycerol were mixed and stirred evenly, and then the solution was poured into a 100 ml reactor and stirred for one hour. Then the reactor was sealed and placed in a 180° C. oven for reaction for 2.5 hours. After the reaction was completed, the reaction mixture was naturally cooled to room temperature. The powder obtained after the reaction was collected, washed with anhydrous ethanol for several times, and dried at 60° C. for 12 hours to obtain cobalt glycerate;

[0033] (2) Preparation of Vco (defective cobalt oxide)

[0034] GlyCo powder was calcined in an oxygen atmosphere at 250 °C for 2 h at a heating rate of 5 °C / min, and the resulting product was Vco;

[0035] (3) Preparation of Pt-Vco catalyst

[0036] Mix 2 mmol of Vco, 10 mol of ethylene glycol and 0.9 mmol of chloroplatinic acid, and ultrasonically treat for 30 minutes. Then pour the solution into a 100 mL reactor, seal the reactor and place it in a 120°C oven to react for 4 hours. After cooling, filter and collect the solids, and dry them at 60°C for 12 hours to obtain a Pt-Vco catalyst.

[0037] Embodiment 2:

[0038] This embodiment relates to a method for preparing a platinum-modified defective cobalt oxide catalyst, comprising the following steps:

[0039] (1) Preparation of GlyCo (cobalt glycerate)

[0040] 6 mmol of cobalt acetate and 0.5 mol of glycerol were stirred evenly, poured into a 100 mL reactor, stirred for 1 hour, and then the reactor was sealed and placed in a 160° C. oven for 4 hours. After the reaction was completed, it was naturally cooled to room temperature, and the powder obtained by the reaction was collected, washed with anhydrous ethanol for several times, and dried at 60° C. for 12 hours to obtain cobalt glycerate as a precursor for preparing defective cobalt oxide;

[0041] (2) Preparation of Vco (defective cobalt oxide)

[0042] GlyCo powder was calcined in an oxygen atmosphere at 350 °C for 1 hour at a heating rate of 5 °C / min, and the resulting product was Vco;

[0043] (3) Preparation of Pt-Vco catalyst

[0044] 4 mmol of Vco, 12 mol of ethylene glycol and 0.6 mmol of chloroplatinic acid were mixed and ultrasonically treated for 30 minutes. The solution was poured into a 100 mL reactor, and then the reactor was sealed and placed in a 140°C oven for reaction for 2 hours. After cooling, the solid items were collected by filtration and dried at 60°C for 12 hours to obtain a platinum-modified defective cobalt oxide (Pt-Vco) catalyst.

[0045] In this example, the crystal structure of the prepared Pt-Vco catalyst was characterized by X-ray powder diffraction spectroscopy (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). Figure 1-3 shown.

[0046] from Figure 1 It can be seen that after Pt loading, Co3O4 (311) crystal plane exists; in addition, Pt shows characteristic diffraction peaks at 39.8° and 46.2°, which correspond well to the card, indicating that the Pt-Vco material is successfully synthesized.

[0047] from Figure 2 It can be seen that the Pt-Vco material is composed of many nanoblocks.

[0048] from Figure 3 It can be seen that after platinum modification, the (400) and Pt (111) crystal planes of Co3O4 exist, confirming that the material synthesis is successful.

[0049] Embodiment 3:

[0050] This embodiment relates to a method for preparing a platinum-modified defective cobalt oxide catalyst, comprising the following steps:

[0051] (1) Preparation of GlyCo (cobalt glycerate)

[0052] After 8 mmol of cobalt nitrate and 0.6 mol of glycerol are stirred evenly, the solution is poured into a 100 ml reactor and stirred for one hour. Then the reactor is sealed and placed in a 140°C oven for reaction for 3 hours. After the reaction is completed, it is naturally cooled to room temperature. The powders are collected, washed with anhydrous ethanol for several times, and dried at 60°C for 12 hours. The purple powder obtained is cobalt glycerate.

[0053] (2) Preparation of Vco (defective cobalt oxide)

[0054] GlyCo powder was calcined in an oxygen atmosphere at 300 °C for 3 h at a heating rate of 5 °C / min, and the resulting product was Vco;

[0055] (3) Preparation of Pt-Vco catalyst

[0056] 6 mmol of Vco, 10 mol of ethylene glycol and 0.8 mmol of chloroplatinic acid were mixed and ultrasonically treated for 30 minutes. Then the solution was poured into a 100 ml reactor. The reactor was sealed and placed in a 150°C oven for reaction for 1 hour. After cooling, the solid matter was collected by filtration and dried at 60°C for 12 hours to prepare a platinum-modified defective cobalt oxide (Pt-Vco) catalyst.

[0057] Embodiment 4:

[0058] This embodiment relates to a method for preparing a platinum-modified defective cobalt oxide catalyst, comprising the following steps:

[0059] (1) Preparation of GlyCo (cobalt glycerate)

[0060] 8 mmol of cobalt acetate and 0.6 mol of glycerol were mixed and stirred evenly, then the solution was poured into a 100 mL reactor and stirred for one hour, then the reactor was sealed and placed in a 140°C oven for reaction for 3 hours, after the reaction was completed, it was naturally cooled to room temperature, the powder obtained by the reaction was collected, washed with anhydrous ethanol for several times, and dried at 60°C for 12 hours, and the purple powder obtained was cobalt glycerate;

[0061] (2) Preparation of Vco (defective cobalt oxide)

[0062] GlyCo powder was calcined in an oxygen atmosphere at 300 °C for 3 h at a heating rate of 5 °C / min, and the resulting product was Vco;

[0063] (3) Preparation of Pt-Vco catalyst

[0064] 6 mmol of Vco, 10 mol of ethylene glycol and 0.8 mmol of platinum nitrate were mixed and ultrasonically treated for 30 minutes. Then the solution was poured into a 100 ml reactor. The reactor was sealed and placed in a 130°C oven for reaction for 2 hours. After cooling, the solid matter was collected by filtration and dried at 60°C for 12 hours to prepare a platinum-modified defective cobalt oxide (Pt-Vco) catalyst.

[0065] Embodiment 5:

[0066] This example involves an electrochemical test experiment of the Pt-Vco catalyst prepared in Example 2, and the specific steps are as follows:

[0067] The Pt-Vco catalyst obtained in Example 2 was used as the working electrode (anode), the Hg / HgO electrode was used as the reference electrode, and the carbon rod electrode was used as the counter electrode. -1HMF was added to the KOH aqueous solution and stirred evenly, and the electrolyte was used (the concentration of HMF in the electrolyte was 10 mmol / L). The electrochemical test was carried out by an electrochemical workstation, including a linear sweep voltammetry test and a stability test of multiple cycles of electrolysis. The stability test was to collect the electrolyte after each electrolysis, and then use a high performance liquid chromatography to detect 5-hydroxymethylfurfural (HMF) molecules and related selective oxidation products. The results are as follows: Figure 4 and Figure 5 As shown; and in the same way, pure Co3O4 and defective cobalt oxide (Vco) were used as working electrodes for linear sweep voltammetry tests, and the results are shown in Figure 4 shown.

[0068] from Figure 4 From the linear sweep voltammetry test of Pt-Vco catalytic oxidation of HMF, it can be seen that the starting potential of Vco is 1.21V, which is lower than the starting potential of pure Co3O4 (1.29V). The starting potential of Pt-Vco is 1.14V, which is the lowest among the three. This means that the construction of metal defects and the introduction of Pt have a significant promoting effect on the activity and performance of HMFOR. The current density of pure Co3O4 at 1.35V is 0.38mA / cm 2 , the current density of Pt-Vco at 1.35V is 7.22mA / cm 2 , Pt-Vco is 19 times higher than pure Co3O4.

[0069] from Figure 5 From the FDCA yield and Faradaic efficiency of the Pt-Vco electrode in six HMFOR cycles, it can be seen that Pt-Vco still maintains a high 2,5-furandicarboxylic acid (FDCA) yield and Faradaic efficiency after 6 cycles, indicating that it has good stability in multiple cycles.

Claims

1. A method for preparing a platinum-modified defective cobalt oxide catalyst, characterized in that: The following steps are involved: (1) Preparing defective cobalt oxide: mixing cobalt salt and glycerol evenly, synthesizing cobalt glycerate by hydrothermal reaction; and then calcining the cobalt glycerate at high temperature to obtain defective cobalt oxide; (2) Preparation of platinum-modified defective cobalt oxide: The obtained defective cobalt oxide and platinum salt are mixed and stirred, and then subjected to a hydrothermal reaction to obtain a platinum-modified defective cobalt oxide (Pt-Vco) catalyst.

2. The method for preparing a platinum-modified defective cobalt oxide catalyst according to claim 1, characterized in that: In the step (1), the cobalt salt is cobalt nitrate or cobalt acetate.

3. The method for preparing a platinum-modified defective cobalt oxide catalyst according to claim 1, characterized in that: The molar ratio of cobalt salt to glycerol is 1:(70-100).

4. The method for preparing a platinum-modified defective cobalt oxide catalyst according to claim 1, characterized in that: The hydrothermal reaction temperature in step (1) is 160-200° C. and the reaction time is 1-4 hours.

5. The method for preparing a platinum-modified defective cobalt oxide catalyst according to claim 1, characterized in that: The high temperature calcination in step (1) is carried out in an oxygen atmosphere at 200 to 400° C. at a heating rate of 5° C. / min for 1 to 4 hours.

6. The method for preparing the platinum-modified defective cobalt oxide catalyst according to claim 1, characterized in that: In the step (2), the platinum salt is platinum nitrate, platinum sulfate or chloroplatinic acid.

7. The method for preparing a platinum-modified defective cobalt oxide catalyst according to claim 1, characterized in that: The principle of the hydrothermal reaction in step (2) also includes ethylene glycol, and the molar ratio of defective cobalt oxide, ethylene glycol and platinum salt is (2-3): (500-10000): (0.3-0.9).

8. The method for preparing the platinum-modified defective cobalt oxide catalyst according to claim 1, characterized in that: In the step (2), the hydrothermal reaction temperature is 100 to 150° C. and the reaction time is 1 to 4 hours.

9. A platinum-modified defective cobalt oxide catalyst prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the platinum-modified defective cobalt oxide catalyst as claimed in claim 9 in the electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF).

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