CN110890559A - Preparation method of carbonized wood loaded PdCo alloy composite electrocatalyst - Google Patents

Abstract

The invention discloses a preparation method of carbonized wood-supported PdCo alloy composite electrocatalyst. Working electrode, spectrally pure graphite rod as auxiliary electrode, mixed solution of palladium chloride, cobalt sulfate and sodium citrate as electrolyte, galvanostatic deposition, PdCo alloy deposited on the surface of carbonized wood to obtain composite electrocatalyst. The present invention uses carbonized wood with a three-dimensional porous network structure as the carrier of the electrocatalyst. Compared with the carbon carrier commonly used in current electrocatalysts, the network structure can provide a more efficient and stable electron transport network and improve the electrical conductivity of the composite electrocatalyst; The structure is beneficial to expose more active sites, increase the electrochemically active area of the electrocatalyst, and at the same time facilitate the rapid penetration and diffusion of the electrolyte, thereby improving the activity and stability of the composite electrocatalyst.

Description

A kind of preparation method of carbonized wood supported PdCo alloy composite electrocatalyst

technical field

The invention belongs to the field of electrocatalytic materials, and in particular relates to a preparation method of a carbonized wood-supported PdCo alloy composite electrocatalyst.

Background technique

Fuel cell is an energy conversion device that can directly convert chemical energy into electrical energy through chemical reaction. It has the advantages of high energy conversion efficiency, low environmental pollution, and wide source of raw materials. It is considered to be the most promising energy conversion device in the 21st century. one. At present, the catalysts used in fuel cells are mainly Pt-based catalysts. Due to the low reserves of Pt, high price, weak resistance to CO poisoning, and poor catalytic stability, the large-scale commercial application of Pt-based catalysts and fuel cells is seriously restricted.

Pd is in the same main group as Pt. It has catalytic activity comparable to Pt in alkaline medium. Its reserves are 50 times that of Pt, and its anti-poisoning ability is better than Pt. Therefore, Pd has been used to replace Pt. Research.

In the research process of Pd-based catalysts, the introduction of transition metals (Co, Ni, Cu, etc.) to form alloys with Pd can not only reduce the amount of Pd and further reduce the cost of catalysts, but also utilize the dual function between the two metals. Catalyst activity and stability. In addition, the preparation of supported composite catalysts can improve the dispersibility of the catalyst, increase the electrochemical active area of the catalyst, and at the same time can effectively inhibit the migration and agglomeration of active components during the catalytic reaction process, thereby improving the activity and stability of the electrocatalyst. Carbon materials have excellent electrical conductivity and chemical stability, as well as good adaptability to different interfaces, making them commonly used supports for current composite electrocatalysts. However, the carbon materials currently used in carbon-supported catalysts are basically prepared using non-renewable fossil resources under relatively harsh conditions, such as chemical vapor deposition and laser etching. are still very limited.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology, and provide a preparation method of a carbonized wood supported PdCo alloy electrocatalyst with low cost, high catalytic activity and stability.

In order to solve the above-mentioned technical problems, the technical scheme proposed by the present invention is:

A preparation method of a carbonized wood-supported PdCo alloy composite electrocatalyst, comprising the following steps:

(1) the wood chips are immersed in the zinc chloride solution for pretreatment, then successively dried, pyrolyzed and carbonized, and cooled to obtain carbonized wood with a three-dimensional porous structure;

(2) using the carbonized wood with the three-dimensional porous structure as the working electrode, the spectroscopically pure graphite rod as the auxiliary electrode, the mixed solution of palladium chloride, cobalt sulfate and sodium citrate as the electrolyte, galvanostatic deposition is carried out, and the PdCo alloy is The carbonized wood supported PdCo alloy composite electrocatalyst is obtained by depositing on the surface of the carbonized wood, and then cleaning and drying.

In the above preparation method, preferably, in the step (1), the concentration of the zinc chloride solution is 0.2-0.4 mol/L, the pretreatment temperature is 25-30 °C, and the time is 12-24 h.

In the above preparation method, preferably, in the step (1), drying refers to drying at 60 to 80°C for 12 to 24 hours; the specific process of pyrolysis and carbonization is as follows: the temperature is raised to a temperature of 2 to 5°C/min. 300-500°C, hold for 1-2h, then heat up to 700-900°C at a heating rate of 2-5°C/min, and hold for 3-5h.

In the above preparation method, preferably, in the step (1), both pyrolytic carbonization and cooling are performed under the protection of nitrogen or argon.

In the above preparation method, preferably, in the step (2), the concentration of palladium chloride in the electrolyte is 0.5-1.0 mmol/L, the concentration of cobalt sulfate is 0.5-1.0 mmol/L, and the concentration of sodium citrate is 0.002-0.006 mmol/L; electrolyte volume is 10-15mL.

In the above preparation method, preferably, in the step (2), the pH value of the electrolyte is adjusted to 3.5-4.5 by using a 2.0 mol/L sodium hydroxide solution. Controlling the electrolyte within this range can ensure the quality of the coating and ensure that the target product is produced.

In the above preparation method, preferably, in the step (2), the current density of the galvanostatic deposition is 0.25-0.5 mA/cm ² , the temperature is 60-80° C., and the time is 1.5-2.5 h.

In the above preparation method, preferably, in the step (2), the diameter of the spectroscopically pure graphite rod is 0.6 cm and the length is 8-10 cm.

In the above-mentioned preparation method, preferably, in the step (1), the wood chips are cut into thin slices along the direction of the cross-section of the wood, the length is 1.5-2.5 cm, the width is 0.5-1.0 cm, and the thickness is 0.1-0.3 cm; The raw material is broadleaf wood.

In the above preparation method, preferably, in the step (2), washing refers to washing with ultrapure water for 3-5 times; drying refers to vacuum drying at 60-80° C. for 12-24 hours.

In the above preparation method, preferably, the Pd loading in the carbonized wood-supported PdCo alloy composite electrocatalyst is 12.8-32.2 μg/cm ² .

Compared with the prior art, the advantages of the present invention are:

(1) The present invention uses the carbonized wood material with a three-dimensional porous network structure as the carrier of the electrocatalyst. Compared with the carbon material carriers (such as carbon black, graphene, etc.) commonly used in electrocatalysts in the prior art, the present invention consists of carbon. The network structure can provide a more efficient and stable electron transport network and improve the conductivity of the composite electrocatalyst; the three-dimensional porous structure is conducive to exposing more active sites, increasing the electrochemical active area of the electrocatalyst, and at the same time, it is beneficial to the electrolyte. Rapid penetration and diffusion are beneficial to improve the activity and stability of composite electrocatalysts.

(2) the present invention first adopts zinc chloride solution to carry out pretreatment before the wood chips are carried out pyrolysis carbonization, by making the surface of the wood fully adsorb the zinc chloride activator, to achieve the purpose of synchronous activation of wood in the pyrolysis carbonization process, Increasing the surface roughness of the carbonized wood and increasing the specific surface area of the carbonized wood can effectively increase the active sites on the surface of the electrocatalyst after loading, which is beneficial to improve the catalytic activity of the composite electrocatalyst.

(3) The present invention uses natural wood as the raw material for preparing the electrocatalyst carbon material carrier. Compared with non-renewable fossil resources, the present invention has the advantages of wide sources, green environmental protection and reproducibility; at the same time, the preparation process is simple and feasible, and can effectively Solve the problems of convenience and sustainability of carbon materials.

Description of drawings

1 is a scanning electron microscope image of the carbonized wood prepared in Example 1 of the present invention.

2 is a scanning electron microscope image of the carbonized wood-supported PdCo alloy composite electrocatalyst prepared in Example 1 of the present invention.

3 is an X-ray powder diffraction pattern of the carbonized wood-supported PdCo alloy composite electrocatalyst prepared in Example 1 of the present invention.

4 is a cyclic voltammogram of the carbonized wood-supported PdCo alloy composite electrocatalyst prepared in Example 1 of the present invention and the carbon-supported PdCo alloy composite electrocatalyst prepared by a conventional method.

5 is the chronoamperometry curves of the carbonized wood-supported PdCo alloy composite electrocatalyst prepared in Example 1 of the present invention and the carbon-supported PdCo alloy composite electrocatalyst prepared by a conventional method.

Detailed ways

In order to facilitate understanding of the present invention, the present invention will be described more comprehensively and in detail below with reference to the accompanying drawings and preferred embodiments of the specification, but the protection scope of the present invention is not limited to the following specific embodiments.

Unless otherwise defined, all technical terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments, and are not intended to limit the protection scope of the present invention.

Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or can be prepared by existing methods.

Example 1:

The preparation method of the carbonized wood-supported PdCo alloy composite electrocatalyst of the present invention, the specific method is as follows:

(1) Cut the basswood in the horizontal direction into wood chips with a length of 2 × 0.5 cm and a thickness of 0.1 cm, wash the wood chips, and then soak the wood chips in a 0.3 mol/L zinc chloride solution at 30°C for 24 hours, and then take them out. Dry in an oven at 80°C for 12h;

(2) Put the dried wood chips in a tube furnace, and under the protection of nitrogen atmosphere, first heat up to 500°C at a heating rate of 5°C/min, keep the temperature for 1 hour, and then heat up at a heating rate of 5°C/min to 900°C, kept for 3 hours, and finally cooled to room temperature under nitrogen protection to obtain three-dimensional porous carbonized wood derived from wood;

(3) Using the carbonized wood prepared in step (2) as a working electrode, a spectroscopically pure graphite rod with a diameter of 0.6 cm and a length of 10 cm as an auxiliary electrode, at 70 ° C, a volume of 10 mL, and an electrolyte with a pH of 4.0 1.5h, wherein, in the electrolyte, the concentration of palladium chloride is 1.0mmol/L, the concentration of cobalt sulfate is 1.0mmol/L, the concentration of sodium citrate is 0.005mmol/L, and the electrolyte is 2.0mol/L. L sodium hydroxide solution to adjust the pH, the current density during the deposition process is 0.5 mA/cm ² , the area of the carbonized wood immersed in the electrolyte is 1 cm ² , after the deposition is taken out and washed with ultrapure water for 3 times, and then at 60 The carbonized wood-supported PdCo alloy composite electrocatalyst was obtained by vacuum drying at ℃ for 12 h.

The scanning electron microscope image of the carbonized wood prepared in this example is shown in FIG. 1 , and it can be seen from FIG. 1 that the wood after carbonization still maintains its three-dimensional porous structure.

Figure 2 shows the scanning electron microscope image of the carbonized wood-supported PdCo alloy composite electrocatalyst prepared in this example. It can be seen from Figure 2 that the PdCo alloy is uniformly supported on the surface of the carbonized wood, and there is basically no agglomeration phenomenon.

FIG. 3 is an X-ray diffraction pattern of the carbonized wood-supported PdCo alloy composite electrocatalyst prepared in this example. It can be seen from the figure that the derived carbonized wood is amorphous carbon, and the material supported on its surface is a PdCo alloy.

The cyclic voltammetry curve of the carbonized wood-supported PdCo alloy composite electrocatalyst prepared in this example for catalytic oxidation of ethanol in 1.0mol/L KOH+1.0mol/LC ₂ H ₅ OH solution is shown in Figure 4, and the scan rate is 50mV/ s, the loading of Pd was 32.2 μg/cm ² , and PdCo/C was prepared by conventional impregnation reduction method using traditional commercial carbon black (Vulcan XC-72C) as the carrier and NaBH ₄ solution as the reducing agent. to make. It can be seen from Fig. 4 that the carbonized wood-supported PdCo alloy composite electrocatalyst prepared by the present invention has a current density of 1000 mA/mg for ethanol oxidation. Significantly improved, indicating that it has better catalytic performance.

FIG. 5 shows the chronoamperometry curves of the carbonized wood-supported PdCo alloy composite electrocatalyst and the PdCo/C catalyst prepared in this example. It can be seen from FIG. 5 that the carbonized wood-supported PdCo alloy composite electrocatalyst prepared in this example has a higher performance than the PdCo/C catalyst. The higher current and slower current decay rate further illustrate that the carbonized wood supported PdCo alloy composite electrocatalyst prepared by the present invention has better catalytic performance and better stability than the PdCo/C catalyst.

Example 2:

The preparation method of the carbonized wood-supported PdCo alloy composite electrocatalyst of the present invention, the specific method is as follows:

(1) Cut the basswood into 2.5×1.0cm long and 0.2cm thick wood chips along the horizontal direction, wash the wood chips, then soak the wood chips in 25°C, 0.2mol/L zinc chloride solution for 24h, take out Dry in an oven at 60°C for 24h;

(2) Put the dried wood chips in a tube furnace, and under the protection of nitrogen atmosphere, first heat up to 400°C at a heating rate of 3°C/min, keep the temperature for 1.5h, and then heat up at a heating rate of 3°C/min The temperature was raised to 800 °C, kept for 4 h, and finally cooled to room temperature under nitrogen protection to obtain three-dimensional porous carbonized wood derived from wood;

(3) Using the carbonized wood prepared in step (2) as a working electrode, a spectroscopically pure graphite rod with a diameter of 0.6 cm and a length of 10 cm as an auxiliary electrode, at 60 ° C, a volume of 10 mL, and an electrolyte with a pH of 4.0 2h, wherein, in the electrolyte, the concentration of palladium chloride is 1.0mmol/L, the concentration of cobalt sulfate is 1.0mmol/L, the concentration of sodium citrate is 0.006mmol/L, and the electrolyte is 2.0mol/L The pH was adjusted with the sodium hydroxide solution, the current density during the deposition process was 0.5mA/cm ² , and the area of the carbonized wood immersed in the electrolyte was 2cm ² . The carbonized wood-supported PdCo alloy composite electrocatalyst was obtained by vacuum drying under the conditions for 12 h.

The Pd loading in the carbonized wood-supported PdCo alloy composite electrocatalyst prepared in this example is 17.5 μg/cm ² , and its ethanol oxidation current density can reach 848 mA/mg.

Example 3:

The preparation method of the carbonized wood-supported PdCo alloy composite electrocatalyst of the present invention, the specific method is as follows:

(1) Cut the basswood into 2.0×1.0cm long and 0.3cm thick wood chips along the horizontal direction, wash the wood chips, and then soak the wood chips in 30℃, 0.4mol/L zinc chloride solution for 12h, take out Dry in an oven at 70°C for 18h;

(2) Put the dried wood chips in a tube furnace, and under the protection of nitrogen atmosphere, first heat up to 300°C at a heating rate of 4°C/min, keep the temperature for 2 hours, and then heat up at a heating rate of 4°C/min to 700°C, kept for 5h, and finally cooled to room temperature under nitrogen protection to obtain three-dimensional porous carbonized wood derived from wood;

(3) Using the carbonized wood prepared in step (2) as a working electrode, a spectroscopically pure graphite rod with a diameter of 0.6 cm and a length of 10 cm as an auxiliary electrode, at 80° C., a volume of 15 mL, and an electrolyte with a pH of 4.5 For 1.5h, in the electrolyte, the concentration of palladium chloride is 0.5mmol/L, the concentration of cobalt sulfate is 0.5mmol/L, the concentration of sodium citrate is 0.003mmol/L, and the electrolyte is 2.0mol/L. L of sodium hydroxide solution to adjust the pH, the current density during the deposition process is 0.3 mA/cm ² , the area of the carbonized wood immersed in the electrolyte is 2 cm ² , after the deposition is taken out and washed with ultrapure water for 3 times, and then at 60 The carbonized wood-supported PdCo alloy composite electrocatalyst was obtained by vacuum drying at ℃ for 12 h.

The Pd loading in the carbonized wood-supported PdCo alloy composite electrocatalyst prepared in this example is 12.8 μg/cm ² , and its ethanol oxidation current density can reach 820 mA/mg.

Claims (10)

1. A preparation method of a carbonized wood loaded PdCo alloy composite electrocatalyst is characterized by comprising the following steps:

(1) immersing the wood chips into a zinc chloride solution for pretreatment, and then sequentially drying, pyrolyzing and carbonizing, and cooling to obtain carbonized wood with a three-dimensional porous structure;

(2) and (2) taking the carbonized wood with the three-dimensional porous structure as a working electrode, a spectral pure graphite rod as an auxiliary electrode, and a mixed solution of palladium chloride, cobalt sulfate and sodium citrate as an electrolyte, performing constant current deposition, depositing the PdCo alloy on the surface of the carbonized wood, and cleaning and drying to obtain the carbonized wood loaded PdCo alloy composite electrocatalyst.

2. The preparation method according to claim 1, wherein in the step (1), the concentration of the zinc chloride solution is 0.2-0.4 mol/L, the pretreatment temperature is 25-30 ℃, and the pretreatment time is 12-24 hours.

3. The preparation method according to claim 1, wherein in the step (1), the drying is performed at 60-80 ℃ for 12-24 h; the specific process of pyrolysis and carbonization comprises the following steps: heating to 300-500 ℃ at a heating rate of 2-5 ℃/min, preserving heat for 1-2 h, then heating to 700-900 ℃ at a heating rate of 2-5 ℃/min, and preserving heat for 3-5 h.

4. The method according to any one of claims 1 to 3, wherein in the step (1), the pyrolysis carbonization and the cooling are performed under the protection of nitrogen or argon.

5. The method according to any one of claims 1 to 3, wherein in the step (2), the concentration of palladium chloride, cobalt sulfate and sodium citrate in the electrolyte is 0.5 to 1.0mmol/L, 0.5 to 1.0mmol/L and 0.002 to 0.006 mmol/L; the volume of the electrolyte is 10-15 mL.

6. The method according to any one of claims 1 to 3, wherein in the step (2), the pH of the electrolyte is adjusted to 3.5 to 4.5 by using 2.0mol/L sodium hydroxide solution.

7. The production method according to any one of claims 1 to 3, wherein in the step (2), the constant-current deposition has a current density of 0.25 to 0.5mA/cm²The temperature is 60-80 ℃, and the time is 1.5-2.5 h.

8. The preparation method according to any one of claims 1 to 3, wherein in the step (2), the spectroscopically pure graphite rod has a diameter of 0.6cm and a length of 8 to 10 cm.

9. The method according to any one of claims 1 to 3, wherein the wood chips in the step (1) are cut into thin pieces having a length of 1.5 to 2.5cm, a width of 0.5 to 1.0cm and a thickness of 0.1 to 0.3cm in the transverse direction of the wood; the raw material of the wood chip is broad-leaved tree wood.

10. The preparation method of any one of claims 1 to 3, wherein the loading amount of Pd in the carbonized wood-supported PdCo alloy composite electrocatalyst is 12.8 to 32.2ug/cm²。

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