CN1299375C - Method for preparing Pt-Ru/C catalyst in use for direct methanol fuel cell - Google Patents

Abstract

A method for preparing a Pt-Ru/C catalyst for a direct methanol fuel cell relates to a method for preparing an anode catalyst for a direct methanol fuel cell. In the present invention, the treated carbon carrier is added to the mixed solution of deionized water and isopropanol to disperse uniformly; Pt and Ru compound precursors are added to the uniformly dispersed carbon-containing slurry, and the uniformly dispersed carbon-supported Pt and The Ru compound precursor slurry was dried under constant temperature magnetic stirring at 50-80°C; the obtained carbon-supported Pt and Ru compound precursor powders were ground in an agate mortar for 10 minutes; the carbon-supported Pt-Ru compound was Reduction in the mixed gas of argon at a temperature of 350-420°C for 1-3 hours. _{The (} NH ₄ ) ₂ PtCl ₆ or (NH ₄ ) ₂ RuCl _{5 of} the present invention is _solid and has a lower decomposition temperature _{; the} spongy Pt Or Ru, forming a porous skeleton structure, which improves the electrochemical activity specific surface area and utilization rate of the catalyst.

Description

Preparation method of Pt-Ru/C catalyst for direct methanol fuel cell

Technical field:

The invention relates to a method for preparing an anode catalyst of a direct methanol fuel cell.

Background technique:

Direct Methanol Fuel Cell (DMFC) uses liquid or gaseous methanol as fuel, without external reforming equipment, and has the advantages of high energy conversion efficiency, no pollution, no noise, simple system structure, high energy density, and convenient fuel portability and replenishment. It is especially suitable for It has attracted much attention in vehicles and portable power supplies. The research of direct methanol fuel cells is currently mainly focused on the research of anode catalysts and alcohol-resisting polymer electrolyte membranes; DMFC has low methanol electrooxidation activity and severe polarization at low temperatures, which are the main reasons for its efficiency loss and need to be further improved. Activity of methanol anode electrocatalysts. The Pt-Ru binary catalyst has a good ability to resist CO poisoning and a high ability to electrooxidize methanol, and has been widely used in DMFC. However, this kind of catalyst is expensive and resources are limited, resulting in the high price of direct methanol fuel cells, making it difficult to realize commercialization. Therefore, people hope to improve the activity and utilization rate of the metal catalyst as much as possible, and reduce the cost of the catalyst. At present, people's research on catalysts is mainly focused on the improvement of traditional preparation methods, and the catalytic activity of Pt-Ru/C catalysts is affected by many factors. The Pt and Ru compound precursors have a significant impact on the performance of the catalyst, and the preparation methods of catalysts using different precursors are different. At present, the precursors widely used are H ₂ PtCl ₆ and RuCl ₃ , and the impregnation reduction method is used to prepare the catalyst with a large particle size and low utilization rate of the catalyst. Using Pt(NH ₃ ) ₄ Cl ₂ , Pt(NH ₃ ) ₂ (NO ₂ ) ₂ and Ru(NH ₃ ) ₄ Cl ₂ as precursors, ion exchange or electrochemical reduction can be used to prepare smaller particle size , a catalyst with high catalytic activity; however, the preparation of precursors such as Pt(NH ₃ ) ₄ Cl ₂ , Pt(NH ₃ ) ₂ (NO ₂ ) ₂ and Ru(NH ₃ ) ₄ Cl ₂ is difficult and expensive. Therefore, finding a more suitable and inexpensive Pt-Ru catalyst precursor has become an urgent task in the research work of direct methanol fuel cells.

Invention content:

The object of the present invention is to provide a method for preparing a Pt-Ru/C catalyst for direct methanol fuel cells. The method has the characteristics of simple preparation process, high activity and utilization rate of the prepared catalyst, and low cost. The method of the present invention is achieved through the following steps: 1. The carbon carrier is processed as follows: 1. the carbon carrier is placed in high-pressure steam for 3-12 hours, and the carbon carrier is taken out and vacuum-dried; 2. the steam is treated The treated carbon carrier is heated to 400-1000°C for 1-3 hours in the inert gas of the tube furnace; 2. Add the above-mentioned treated carbon carrier to the mixed solution of deionized water and isopropanol, and disperse evenly; 3. 1. Add the Pt and Ru compound precursors to the uniformly dispersed carbon-containing slurry, so that the Pt and Ru compound precursors are evenly dispersed on the carbon carrier; Make it dry under constant temperature magnetic stirring at 80°C; 5. Grind the obtained carbon-supported Pt and Ru compound precursor powder in an agate mortar for 10 minutes; 6. Mix the carbon-supported Pt and Ru compound in hydrogen and argon The Pt-Ru/C catalyst for the direct methanol fuel cell can be obtained by reducing for 1-3 hours in the gas at a temperature of 350-420°C. The carbon carrier is VulcanXC-72 carbon powder produced by Cabot Corporation. The Pt and Ru compound precursors are (NH ₄ ) ₂ PtCl ₆ and (NH ₄ ) ₂ RuCl ₅ . The Pt precursor compatible with (NH ₄ ) ₂ RuCl ₅ is H ₂ PtCl ₆ , Pt(NH ₃ ) ₄ Cl ₂ or Pt(NH ₃ ) ₂ (NO ₂ ) ₂ . The Ru precursor compatible with (NH ₄ ) ₂ PtCl ₆ is Ru(OH) ₃ , Ru(NO ₃ ) ₂ , RuCl ₃ or Ru(NH ₃ ) ₄ Cl ₂ . The pressure of the high-pressure steam in the step 1 is 0.1-1.5 MPa. The volume ratio of deionized water and isopropanol in the mixed solution of deionized water and isopropanol in the step 2 is 1:1. The (NH ₄ ) ₂ PtCl ₆ or (NH ₄ ) ₂ RuCl ₅ of the present invention is solid, easy to prepare, and has a low decomposition temperature; the main reason for the good performance of the Pt-Ru/C catalyst using it as a precursor is (NH ₄ ) ₂ PtCl ₆ or (NH ₄ ) ₂ RuCl ₅ is reduced to form a sponge-like Pt or Ru, which forms a porous skeleton structure, which increases the specific surface area of the electrochemical activity of the catalyst and facilitates the diffusion of methanol in the catalyst. , improve the utilization of the catalyst. The spongy porous Pt-Ru particles are relatively large, about 10nm in size. The invention has the advantages of simple preparation process, high activity and utilization rate of the prepared catalyst, and low cost.

Detailed ways:

Specific embodiment one: the method of this embodiment is realized through the following steps: 1. The carbon carrier is processed as follows: 1. the carbon carrier is placed in high-pressure steam for 3-12 hours, and the carbon carrier is taken out and vacuum-dried ; ② Heat the steam-treated carbon carrier to 400-1000°C for 1-3 hours in an inert gas tube furnace; 2. Add the above-mentioned treated carbon carrier to the mixed solution of deionized water and isopropanol disperse uniformly; 3. add the Pt and Ru compound precursors to the uniformly dispersed carbon-containing slurry, so that the Pt and Ru compound precursors are uniformly dispersed on the carbon carrier; 4. The uniformly dispersed carbon-supported Pt and Ru compounds Dry the precursor slurry under constant temperature magnetic stirring at 50-80°C; 5. Grind the obtained carbon-supported Pt and Ru compound precursor powder in an agate mortar for 10 minutes; 6. Put the carbon-supported Pt and Ru compound on The Pt-Ru/C catalyst for the direct methanol fuel cell can be obtained by reducing in the mixed gas of hydrogen and argon at a temperature of 350-420° C. for 1-3 hours. The carbon carrier is Vulcan XC-72 carbon powder produced by Cabot Corporation. The Pt and Ru compound precursors are (NH ₄ ) ₂ PtCl ₆ and (NH ₄ ) ₂ RuCl ₅ . The Pt precursor compatible with (NH ₄ ) ₂ RuCl ₅ is H ₂ PtCl ₆ , Pt(NH ₃ ) ₄ Cl ₂ or Pt(NH ₃ ) ₂ (NO ₂ ) ₂ . The Ru precursor compatible with (NH ₄ ) ₂ PtCl ₆ is Ru(OH) ₃ , Ru(NO ₃ ) ₂ , RuCl ₃ or Ru(NH ₃ ) ₄ Cl ₂ . The pressure of the high-pressure steam in the step 1 is 0.1-1.5 MPa. The volume ratio of deionized water and isopropanol in the mixed solution of deionized water and isopropanol in the step 2 is 1:1.

Specific embodiment two: Weigh 200mg of Vulcan XC-72 carbon powder produced by Cabot Company after water vapor and heat treatment, add it to the mixed solution of deionized water and isopropanol, and disperse evenly; add 87.8mg (NH ₄ ) ₂ PtCl ₆ and 25.7mg Ru(OH) ₃ were uniformly dispersed on the carbon carrier, and dried under constant temperature magnetic stirring at 60°C to obtain carbon-supported (NH ₄ ) ₂ PtCl ₆ and Ru(OH) ₃ powders, which were ground on agate Grind in a bowl for 10 minutes. Then the obtained carbon-supported (NH ₄ ) ₂ PtCl ₆ and Ru(OH) ₃ powders were placed in a tube furnace at a temperature of 360 °C in a mixed gas of hydrogen and argon (volume ratio 1:1). Conditions, reduction for 2 hours. The prepared Pt-Ru/C catalyst has a particle size of 8-10nm and an electrochemically active specific surface area of 81.22m ² /g.

Specific embodiment three: Weigh 200 mg of Vulcan XC-72 carbon powder produced by Cabot Company after steam and heat treatment, add it to the mixed solution of deionized water and isopropanol, and disperse evenly; add 87.8 mg (NH ₄ ) ₂ PtCl ₆ and 0.84ml 0.2mol/L RuCl ₃ , so that they were uniformly dispersed on the carbon carrier, and dried under constant temperature magnetic stirring at 80°C to obtain carbon-supported (NH ₄ ) ₂ PtCl ₆ and RuCl ₃ powders, which were placed in an agate mortar Grind for 10 minutes. Then the obtained carbon-supported (NH ₄ ) ₂ PtCl ₆ and RuCl ₃ powders were placed in a tube furnace, and reduced to 2 hours. The prepared Pt-Ru/C catalyst has a particle size of 8-10 nm and an electrochemically active specific surface area of 89.81 m ² /g.

Specific embodiment four: Weigh 200 mg of Vulcan XC-72 carbon powder produced by Cabot Company after water vapor and heat treatment, add it to the mixed solution of deionized water and isopropanol, and disperse evenly; add 87.8 mg (NH ₄ ) ₂ PtCl ₆ and 1.84ml 0.0917mol/L Ru(NO ₃ ) ₂ , dispersed evenly on the carbon support, and dried under constant temperature magnetic stirring at 70°C to obtain carbon-supported (NH ₄ ) ₂ PtCl ₆ and Ru(NO ₃ ) ₂ powder, grind in an agate mortar for 10 minutes. Then the obtained carbon-supported (NH ₄ ) ₂ PtCl ₆ and Ru(NO ₃ ) ₂ powders were placed in a tube furnace at a temperature of 360 °C in a mixed gas of hydrogen and argon (volume ratio 1:1). Conditions, reduction for 2 hours. The prepared Pt-Ru/C catalyst has a particle size of 9-11nm and an electrochemically active specific surface area of 78.53m ² /g.

Specific embodiment five: Weigh 200mg of Vulcan XC-72 carbon powder produced by Cabot Company through water vapor and heat treatment, add it to the mixed solution of deionized water and isopropanol, and disperse evenly; add 43.5mg (NH ₄ ) ₂ RuCl ₅ and 1.46ml 0.1158mol/L H ₂ PtCl ₆ , so that they were uniformly dispersed on the carbon carrier, and dried under constant temperature magnetic stirring at 70°C to obtain carbon-supported (NH ₄ ) ₂ RuCl ₅ and H ₂ PtCl ₆ powders, on agate Grind in a mortar and mortar for 10 minutes. Then the obtained carbon-supported (NH ₄ ) ₂ RuCl ₅ and H ₂ PtCl ₆ powders were placed in a tube furnace at a temperature of 380°C in a mixed gas of hydrogen and argon (volume ratio 1:1). , Restored for 2.5 hours. The prepared Pt-Ru/C catalyst has a particle size of 7-9nm and an electrochemically active specific surface area of 69.78m ² /g.

Specific embodiment six: Weigh 200 mg of Vulcan XC-72 carbon powder produced by Cabot Company after water vapor and heat treatment, add it to the mixed solution of deionized water and isopropanol, and disperse evenly; add 43.5 mg (NH ₄ ) ₂ RuCl ₅ and 6.78ml 0.0249mol/L Pt(NH ₃ ) ₄ Cl ₂ , which were uniformly dispersed on the carbon support, and dried under constant temperature magnetic stirring at 50°C to obtain carbon-supported (NH ₄ ) ₂ RuCl ₅ and Pt(NH ₃ ) ₄ Cl ₂ powder, ground in an agate mortar for 10 minutes. Then the obtained carbon-supported (NH ₄ ) ₂ RuCl ₅ and Pt(NH ₃ ) ₄ Cl ₂ powders were placed in a tube furnace in a mixed gas of hydrogen and argon (volume ratio 1:1) at a temperature of Under the condition of 370°C, reduce for 2 hours. The prepared Pt-Ru/C catalyst has a particle size of 7-9nm and an electrochemically active specific surface area of 75.68m ² /g.

Embodiment 7: Weigh 200 mg of Vulcan XC-72 carbon powder produced by Cabot Company after steam and heat treatment, add it to the mixed solution of deionized water and isopropanol, and disperse evenly; add 43.5 mg (NH ₄ ) ₂ RuCl ₅ and 6.77ml 0.0249mol/L Pt(NH ₃ ) ₂ (NO ₂ ) ₂ , which were uniformly dispersed on the carbon carrier, and dried under constant temperature magnetic stirring at 50°C to obtain carbon-supported (NH ₄ ) ₂ RuCl ₅ and Pt(NH ₃ ) ₂ (NO ₂ ) ₂ powder, ground in an agate mortar for 10 minutes. Then the obtained carbon-supported (NH ₄ ) ₂ RuCl ₅ and Pt(NH ₃ ) ₂ (NO ₂ ) ₂ powders were placed in a tube furnace in a mixed gas of hydrogen and argon (volume ratio 1:1) 1. Under the condition of 360°C, reduce for 2 hours. The prepared Pt-Ru/C catalyst has a particle size of 8-11nm and an electrochemically active specific surface area of 92.8m ² /g.

Claims (4)

1. The preparation method of Pt-Ru/C catalyst for direct methanol fuel cell is characterized in that it is realized through the following steps: 1. The carbon carrier is processed as follows: 1. The carbon carrier is placed in high-pressure steam for processing 3 -12 hours, take out the carbon carrier and dry it in vacuum; ②Heat the steam-treated carbon carrier to 400-1000°C in the inert gas of the tube furnace for 1-3 hours; 2. Add the above-mentioned treated carbon carrier In the mixed solution of deionized water and isopropanol, disperse evenly; 3. Add the Pt and Ru compound precursors to the uniformly dispersed carbon-containing slurry, so that the Pt and Ru compound precursors are evenly dispersed on the carbon carrier; 4. 1. Dry the homogeneously dispersed carbon-supported Pt and Ru compound precursor slurry under constant temperature magnetic stirring at 50-80°C; 5. Grind the obtained carbon-supported Pt and Ru compound precursor powder in an agate mortar for 10 minutes 6. Reducing the carbon-supported Pt and Ru compounds in a mixed gas of hydrogen and argon at a temperature of 350-420°C for 1-3 hours to obtain the Pt-Ru/C catalyst for direct methanol fuel cells; The precursors of Pt and Ru compounds are (NH ₄ ) ₂ PtCl ₆ and (NH ₄ ) ₂ RuCl ₅ ; the Pt precursors matched with (NH ₄ ) ₂ RuCl ₅ are H ₂ PtCl ₆ , Pt(NH ₃ ) ₄ Cl ₂ or Pt(NH ₃ ) ₂ (NO ₂ ) ₂ ; the Ru precursor compatible with (NH ₄ ) ₂ PtCl ₆ is Ru(OH) ₃ , Ru(NO ₃ ) ₂ , RuCl ₃ or Ru (NH ₃ ) ₄ Cl ₂ . 2. The method for preparing a Pt-Ru/C catalyst for direct methanol fuel cells according to claim 1, characterized in that the pressure of the high-pressure steam in the first step is 0.1-1.5 MPa. 3. The preparation method of Pt-Ru/C catalyst for direct methanol fuel cell according to claim 1, characterized in that the mixed solution of deionized water and isopropanol in said step 2 is deionized water and isopropanol The volume ratio is 1:1. 4. The preparation method of Pt-Ru/C catalyst for direct methanol fuel cell according to claim 1, characterized in that the particle diameter of the Pt-Ru/C catalyst is 8-11 nm.