CN104689852B - Preparation of benzotriazole modified and carbon carrier loaded palladium-based catalyst - Google Patents

Abstract

The invention provides a preparation method of a benzotriazole-modified carbon carrier-loaded palladium-based catalyst applied in a fuel cell. The carbon material and benzotriazole are dissolved in an organic solvent and stirred for 2 to 24 h , remove the solvent, and dry to obtain a carbon carrier modified by benzotriazole; dissolve palladium chloride or a mixture of palladium chloride and metal salt in a protic solvent, add a complexing agent and a carbon carrier modified by benzotriazole After reacting at high temperature for a period of time, cooling, washing with water and drying, a palladium-based catalyst supported on a modified carbon carrier is obtained. Compared with the palladium-based nanoparticles loaded by the traditional C carrier, the carrier prepared by the invention has better catalytic performance and stability, simple preparation process and low price, and is an excellent palladium-based catalyst applicable to fuel cells.

Description

Preparation of Palladium-Based Catalysts on Carbon Supports Modified by Benzotriazole

technical field

The invention relates to the preparation of a modified carbon carrier-loaded palladium-based catalyst, in particular to the preparation of a benzotriazole-modified carbon carrier-loaded palladium-based catalyst, which belongs to the technical field of fuel cells.

Background technique

High-efficiency and low-emission fuel cells are recognized as clean energy conversion systems, but catalysts are a major constraint to their commercialization. Noble metals represented by platinum bases are the most ideal catalysts. It is catalytically active for both the cathodic and anode reactions of the fuel cell and can work for a long time. However, precious metals such as platinum have limited reserves and are expensive. In addition, platinum-based catalysts have low electrocatalytic activity and are easily poisoned by intermediate products. Therefore, reducing the cost of catalysts and preparing catalysts with low noble metal loading and high catalytic activity are the key to realize the commercialization of fuel cells. In the field of catalysts, on the one hand, people are looking for catalysts with low noble metal content and high catalytic activity, and studying nanoparticles with different components or special structures such as special shapes, alloys, and core-shell structures; on the other hand, they are looking for various high-performance supports.

The most widely used catalyst support in fuel cells is carbon powder (VulcanXC-72). Carbon powder is not only cheap and easy to prepare, it also has the following characteristics: large surface area, high conductivity, and special pore structure. However, when the fuel cell is started and stopped, the carbon support is easily corroded, which will cause the agglomeration of nanoparticles supported on its surface, seriously affecting the performance of the catalyst, thereby reducing the life of the catalyst. Since the modified carbon support can change the interaction between the support and the metal particles, it can improve the dispersion of nanoparticles on the support, reduce the onset potential of the catalyst, and then improve the activity and durability of the catalyst. Therefore, modification of carbon materials is an effective way to improve the performance of catalysts.

At present, the commonly used methods for preparing modified carbon supports mainly include the following: chemical vapor deposition, high temperature pyrolysis, nitrogen atom sputtering, etc. Although the above method can effectively improve the performance of the carbon support and increase the activity of the catalyst, it also has certain defects, such as the required temperature is too high, the preparation process is cumbersome, the cost is high, and it is difficult to commercialize it. In addition, compared with platinum, palladium has attracted widespread attention due to its cheap price, abundant reserves, high catalytic activity and high anti-poisoning ability. Therefore, replacing platinum with palladium and developing low-cost, high-activity and stable catalysts is the key to realize the commercialization of fuel cells.

Contents of the invention

The purpose of the present invention is to provide a kind of preparation method of the palladium-based catalyst supported on the carbon support of a kind of benzotriazole modification.

1. Preparation of benzotriazole-modified carbon support palladium-based catalyst

(1) Preparation of benzotriazole-modified carbon supports: carbon materials and benzotriazole (TBA) were dissolved in an organic solvent at a mass ratio of 0.5:1 to 20:1, and were heated at 20 to 60 °C. Stir the reaction for 2-24 h, remove the solvent, and dry to obtain a carbon carrier modified by benzotriazole; the organic solvent is at least one of methanol, ethanol, ethylene glycol, glycerol, benzene, toluene, and chloroform;

(2) Preparation of supported palladium-based catalyst: Dissolve palladium chloride or a mixture of palladium chloride and metal salt in a protic solvent, add complexing agent to disperse evenly, stir for 20-60 min, adjust pH=7-12; add The benzotriazole-modified carbon support prepared above was stirred and ultrasonically dispersed for 30-80 min, then reacted at 150-180 °C for 4-8 h, cooled, washed with water, and dried to obtain the modified carbon support-loaded palladium-based catalyst.

Described metal salt is the chloride salt of cobalt, nickel, silver, iron, tin, copper; Palladium chloride and metal salt are mixed with the mass ratio of 0.2:1～5:1; Described protic solvent is hydrazine, ethylene glycol Alcohol, glycerol, aqueous solution of sodium borohydride or ethanol; The complexing agent is triethanolamine, sodium citrate, sodium tartrate, EGTA, sodium hexametaphosphate, EDTA; palladium chloride or palladium chloride and metal The mass ratio of the salt mixture and the complexing agent is 0.2:1 ~ 5:1; the mass ratio of the above-mentioned palladium chloride or palladium chloride to the metal salt mixture and the carbon support modified by benzotriazole is 1:3 ~ 1: 6 .

2. Structure and performance of palladium-based catalysts supported on modified carbon supports

The structure of the catalyst (Pd/BTA-C) and the electrocatalytic performance of ethanol will be described below by taking the modified carbon carrier supported palladium nanoparticles as an example. At the same time, it was compared with the Pd/C catalyst prepared by the same method.

Figure 1 is the X-ray diffraction (XRD) patterns of Pd/BTA-C and Pd/C catalysts. As can be seen from Figure 1, there is a characteristic diffraction peak of the face-centered cubic structure of Pd in the Pd/BTA-C catalyst prepared by the present invention, indicating that the palladium nanoparticles loaded on it have a face-centered cubic structure.

Figure 2 is a transmission electron microscope image of the Pd/BTA-C catalyst. It can be seen from Figure 2 that the palladium nanoparticles are evenly distributed on the modified carbon support without agglomeration.

Figure 3 is a particle size distribution diagram of the Pd/BTA-C catalyst. It can be seen from Figure 3 that the average particle size is 4.2 + 0.3nm.

Figure 4 is the cyclic voltammetry test of Pd/BTA-C and Pd/C catalysts in 0.1 M KOH solution. The electrochemically active areas of the two catalysts can be calculated from the reduction peaks in Figure 3, which are 312.78 cm ² /mg and 582.98 cm ² /mg, respectively, indicating that the electrochemically active area of Pd/BTA-C is significantly larger than that of Pd/C.

Figure 5 is the cyclic voltammetry test of Pd/BTA-C and Pd/C catalysts in 0.1 M KOH + 0.5 MC ₂ H ₅ OH solution. It can be seen from Figure 4 that the onset potential of Pd/BTA-C is not only negatively shifted by 70 mV compared with Pd/C, but also its oxidation peak current density is 175.25 mA/mg _Pd , which is 1.72 times that of Pd/C catalyst.

Fig. 6 is the chronoamperometric diagram of Pd/BTA-C and Pd/C catalysts in 0.1 M KOH + 0.5 MC ₂ H ₅ OH solution. The results show that after 3000 s, the current density of Pd/BTA-C is 25.72 mA / mg _Pd , and that of Pd/C is 19.53 mA / mg _Pd (only 75.9 % of the current density of Pd/BTA-C), while the same as the initial current Compared with density, the attenuation of Pd/BTA-C is 57.4%, and the attenuation of Pd/C is 69.7%. It shows that Pd/BTA-C has better stability.

In summary, the benzotriazole-modified carbon carrier-supported palladium-based catalyst of the present invention effectively improves the catalytic performance of metal nanoparticles. In addition, the synthesis process of the present invention is simple, low in cost, and has good catalytic activity and stability, and is an excellent palladium-based catalyst applicable to fuel cells.

Description of drawings

Figure 1 is the X-ray diffraction (XRD) patterns of Pd/BTA-C and Pd/C catalysts.

Figure 2 is a transmission electron microscope image of the Pd/BTA-C catalyst.

Figure 3 is a particle size distribution diagram of the Pd/BTA-C catalyst.

Figure 4 is the cyclic voltammetry test of Pd/BTA-C and Pd/C catalysts in 0.1 M KOH solution.

Figure 5 shows the catalytic ethanol performance test of Pd/BTA-C and Pd/C catalysts in 0.1 M KOH + 0.5 MC ₂ H ₅ OH solution.

Figure 6 shows the chronoamperograms of Pd/BTA-C and Pd/C catalysts at -0.2 V in the ethanol oxidation reaction and the corresponding current density histograms after 3000 s.

Fig. 7 is a histogram of current density corresponding to Pd/BTA-C and Pd/C catalysts after ethanol oxidation reaction for 3000 s.

detailed description

The preparation and electrocatalytic performance of the palladium-based catalyst of the present invention will be further described below through specific examples.

The preparation of embodiment 1, Pd/BTA-C catalyst

Add 500 mg of carbon powder and 100 mg of benzotriazole (BTA) into a 100 mL round bottom flask, dissolve in 40 mL of ethanol, stir for 18 h; remove the solvent and dry at 50 °C for 7 h to obtain the carrier BTA -C;

Add 41.68 mg of palladium chloride into a 100 mL round bottom flask, dissolve with 5~10 drops of concentrated hydrochloric acid, add 30 mL of ethylene glycol, 150 mg of sodium citrate, and stir for 1 h after complete dissolution; adjust the pH =9, then add 100 mg of the above-prepared carrier BTA-C, stir for 30 min, and sonicate for 1 h; then reflux at 160°C for 6 h, cool, filter with suction, and dry at 50°C to obtain Pd/BTA-C catalyst.

In the performance test of catalytic ethanol oxidation, the oxidation peak current density of the Pd/BTA-C catalyst was 175.25 mA /mg _Pd , which was 1.72 times that of the Pd/C catalyst, and the onset potential shifted negatively by 70 mV; In the test, the current density of Pd/BTA-C after 3000 s was 25.72 mA/mg _Pd , which was 1.3 times that of Pd/C.

The preparation of embodiment 2, PdNi/BTA-C catalyst

Add 500 mg of carbon powder and 150 mg of benzotriazole (BTA) into a 100 mL round bottom flask, dissolve them in about 40 mL of ethanol, stir for 18 h, remove the solvent, and dry at 50 °C for 7 h. Obtain carrier BTA-C;

Add 26.61 mg of palladium chloride and 35.65 mg of nickel chloride into a 100 mL round bottom flask, dissolve with 4 to 8 drops of concentrated hydrochloric acid, then add 30 mL of ethylene glycol and 100 mg of sodium citrate; Stir the reaction for 1 h, adjust the pH=8 ~ 9, then add 100 mg of the prepared carrier BTA-C prepared above, stir for 30 min, and sonicate for 1 h; then reflux at 160 ° C for 6 h, cooling, suction filtration, Dry at 50°C to obtain a PdNi/BTA-C catalyst.

In the performance test of catalytic methanol oxidation, the oxidation peak current density of the PdNi/BTA-C catalyst was 173.60 mA/mg _Pd , which was 1.7 times that of the Pd/C catalyst, and the onset potential shifted negatively by 60 mV; at -0.1 V In the current test, the current density of PdNi/BTA-C after 3000s is 24.38 mA / mg _Pd , which is 1.25 times that of Pd/C catalyst and Pd/C.

The preparation of embodiment 3, PdCo/BTA-C catalyst

Add 600 mg of carbon powder and 150 mg of benzotriazole (BTA) into a 100 mL round bottom flask, dissolve them in about 40 mL of ethanol, stir for 20 h, remove the solvent, and dry at 50 °C for 7 h. Obtain carrier BTA-C;

Add 26.83 mg of palladium chloride and 35.98 mg of cobalt chloride into a 100 mL round bottom flask, dissolve with 4~7 drops of concentrated hydrochloric acid, add 30 mL of ethylene glycol and 80 mg of sodium citrate; stir after complete dissolution After reacting for 1 h, adjust the pH to 8–9, add 100 mg of the carrier prepared above, stir for 30 min, and sonicate for 1 h; then reflux at 160 °C for 6 h, cool, filter, and dry at 50 °C to obtain PdCo /BTA-C catalyst.

In the performance test of catalytic ethanol oxidation, the oxidation peak current density of the PdCo/BTA-C catalyst was 178.71 mA/mg _Pd , which was 1.75 times that of the Pd/C catalyst, and the onset potential shifted negatively by 58 mV; In the test, the current density of PdCo/BTA-C after 3000 s is 25.39 mA/mg _Pd , which is 1.3 times that of Pd/C.

The preparation of embodiment 4, PdAg/BTA-C catalyst

Add 500 mg of carbon powder and 200 mg of benzotriazole (BTA) into a 100 mL round bottom flask, dissolve them in about 40 mL of ethanol, stir for 20 h, remove the solvent, and dry at 50 °C for 7 h. Obtain carrier BTA-C;

Add 20.69 mg of palladium chloride and 19.82 mg of silver nitrate into a 100 mL round-bottomed flask, dissolve with 2 to 6 drops of concentrated hydrochloric acid, add 30 mL of ethylene glycol, and 100 mg of sodium citrate. After completely dissolving, stir Reaction 1, adjust the pH to 9 ~ 10, then add 100 mg of the carrier prepared above, stir for 30 min, and sonicate for 1 h; then reflux at 160 °C for 6 h, cool, filter, and dry at 50 °C to obtain PdAg/ BTA-C catalyst.

In the performance test of catalyzing the oxidation of ethylene glycol, the oxidation peak current density of the PdAg/BTA-C catalyst was 174.63 mA / mg _Pd , which was 1.71 times that of the Pd/C catalyst, and the onset potential shifted negatively by 64 mV; at -0.2 V In the chronoamperometry test, the current density of PdAg/BTA-C after 3000 s is 21.68 mA / mg _Pd , which is 1.11 times that of Pd/C catalyst.

The preparation of embodiment 5, PdFe/BTA-C catalyst

Add 600 mg of carbon powder and 200 mg of benzotriazole (BTA) into a 100 mL round bottom flask, dissolve them in about 40 mL of ethanol, stir for 21 h, remove the solvent, and dry at 50 °C for 7 h to obtain Carrier BTA-C;

Add 27.30 mg of palladium chloride and 41.60 mg of ferric chloride into a 100 mL round bottom flask, then add 30 mL of ethylene glycol and 100 mg of sodium citrate, and stir for 1 h after complete dissolution; adjust the pH of the solution =8 ~ 9, then add 100 mg of the above-prepared carrier, stir for 30 min, and sonicate for 1 h; then reflux at 180 °C for 4 h, cool, filter with suction, and dry at 50 °C to obtain the PdFe/BTA-C catalyst .

In the performance test of catalytic methanol oxidation, the oxidation peak current density of the PdFe/BTA-C catalyst was 125.61 mA/mg _Pd , which was 1.23 times that of the Pd/C catalyst, and the onset potential shifted negatively by 50 mV; In the test, the current density of PdFe/BTA-C after 3000 s is 22.50 mA/mg _Pd , which is 1.15 times that of Pd/C catalyst.

Embodiment 6, the preparation of PdSn/BTA-C catalyst

Add 550 mg of carbon powder and 150 mg of benzotriazole (BTA) into a 100 mL round bottom flask, dissolve them in about 40 mL of ethanol, stir for 18 h, remove the solvent, and dry at 50 °C for 7 h to obtain Carrier BTA-C;

Add 19.70 mg of palladium chloride and 38.94 mg of tin chloride into a 100 mL round bottom flask, then add 30 mL of ethylene glycol and 75 mg of sodium citrate. After completely dissolving, stir the reaction for 1 h and adjust the pH to After 8 to 9 minutes, add 100 mg of the carrier prepared above, stir for 0.5 h, sonicate for 1 h, then reflux at 170 °C for 5 h, cool, filter with suction, and dry at 50 °C to obtain the PdSn/BTA-C catalyst.

In the performance test of catalytic glycerol oxidation, the oxidation peak current density of the PdSn/BTA-C catalyst was 163.39mA/mg _Pd , which was 1.6 times that of the Pd/C catalyst, and the onset potential shifted negatively by 65 mV; In the current test, the current density of PdSn/BTA-C after 3000 s is 20.51 mA/mg _Pd , which is 1.05 times that of Pd/C catalyst.

Claims (4)

1. the carbon carrier of benzotriazole modification loads the preparation method of palladium-based catalyst, comprises the following steps that：

（1）The preparation of the carbon carrier of benzotriazole modification：By material with carbon element and benzotriazole with 0.5:1 ~ 20:1 quality In than being dissolved in organic solvent, the h of stir process 2 ~ 24 at 20 ~ 60 DEG C removes solvent, is dried, and obtains benzotriazole The carbon carrier of modification；

（2）The preparation of load palladium-based catalyst：Palladous chloride. or Palladous chloride. are dissolved in protonic solvent with metal salt mixture, Add chelating agent ultrasonic disperse uniformly to stir 20 ~ 60 min afterwards, adjust pH=7 ~ 12；Add the carbon of benzotriazole modification Then carrier, stirring, each 30 ~ 80 min of ultrasonic disperse react 4 ~ 8 h at 150 ~ 180 DEG C, cool down, wash, do It is dry, obtain final product modified carbon carrier supported palladium base catalyst；

The slaine is cobalt, nickel, silver, ferrum, stannum, the chlorate of copper；

The mass ratio of the carbon carrier that the Palladous chloride. or Palladous chloride. are modified with metal salt mixture and benzotriazole is 1:3~1: 6；

The chelating agent is triethanolamine, sodium citrate, sodium tartrate, EGTA, sodium hexameta phosphate or EDTA；

Palladous chloride. or Palladous chloride. and the mass ratio of metal salt mixture and chelating agent are 0.2:1 ~ 5:1.

2. the carbon carrier of benzotriazole modification as claimed in claim 1 loads the preparation method of palladium-based catalyst, and its feature exists In：Step（1）In organic solvent be methanol, ethanol, ethylene glycol, glycerol, benzene, toluene, at least one of chloroform.

3. the carbon carrier of benzotriazole modification as claimed in claim 1 loads the preparation method of palladium-based catalyst, and its feature exists In：Step（2）In, Palladous chloride. is with slaine with 0.2:1 ~ 5:1 mass ratio mixing.

4. the carbon carrier of benzotriazole modification as claimed in claim 1 loads the preparation method of palladium-based catalyst, and its feature exists In：Step（2）In protonic solvent for hydrazine, ethylene glycol, glycerol, the aqueous solution of sodium borohydride or ethanol aqueous solution.