CN102593473A - Fuel cell catalyst and preparation method thereof - Google Patents

Abstract

The invention provides a fuel cell catalyst, which comprises: a composite carrier prepared from rare earth oxides and carbon carriers; and noble metals loaded on the composite carrier. The catalyst provided by the invention has good anti-poisoning ability. The invention also provides a preparation method of the fuel cell catalyst. Including, a) mixing the carbon carrier with an acidic salt solution containing rare earth elements to obtain a suspension; b) precipitating the rare earth elements in the suspension with an alkaline substance to obtain a carbon carrier composited with hydroxides of rare earth elements; c) sintering the carbon carrier composited with the hydroxide of the rare earth element to obtain a composite carrier; d) mixing a precursor of a noble metal with the composite carrier, and microwave sintering to obtain a fuel cell catalyst. The preparation method provided by the invention is simple and controllable, and has high production efficiency.

Description

A kind of fuel cell catalyst and preparation method thereof

technical field

The invention relates to the field of fuel cells, in particular to a fuel cell catalyst and a preparation method thereof.

Background technique

A direct liquid fuel cell is an electrochemical reaction device that directly uses liquid fuel (such as methanol, formic acid, ethanol) and oxygen in the air to convert chemical energy into electrical energy. Because of its high energy conversion efficiency, simple structure, safety and reliability, cleanliness, and no need for complicated external equipment such as reforming, heating, cooling devices, pressure pumps, fans, etc., it is considered to be the most likely to achieve commercial application first. Fields such as small portable mobile power supplies and sensors have broad application prospects.

At present, direct liquid fuel cells generally use noble metal Pt or Pd as the main active component to be loaded on a carbon carrier with high specific surface area and good conductivity, but because Pt or Pd catalysts are prone to poisoning during use, Thereby reducing the activity of the catalyst. In order to improve the anti-poisoning ability of the catalyst, the researchers proposed to reduce the poisoning effect by modifying Pt or Pd, such as preparing binary or multi-element alloys of Pt or Pd and other metals, looking for more suitable catalyst supports such as carbon nanotubes, And the use of metal oxides to improve its activity, etc. Some researchers have also proposed different improved preparation methods to improve the performance of the corresponding catalysts, such as Chinese patents 02155255.X, 02116449.5, 200710031598.0. However, the effect of these methods on improving the anti-poisoning ability is not obvious.

Contents of the invention

The technical problem to be solved by the present invention is to provide a fuel cell catalyst with good anti-poisoning ability.

In order to solve the above technical problems, the present invention provides a fuel cell catalyst, comprising:

Composite carrier, prepared from rare earth oxide and carbon carrier;

Noble metals are loaded on the composite carrier.

Preferably, the rare earth oxides are oxides of 15 lanthanide elements with atomic numbers from 57 to 71 and seventeen elements including scandium and yttrium.

Preferably, the noble metal is one or more of Pt, Pd, Au, Ir, Ru, Rh, Ag and Os,

Preferably, the carbon support is carbon nanotube, activated carbon, carbon fiber, graphene or carbon gel.

The present invention also provides a preparation method of fuel cell catalyst, comprising:

a) mixing the carbon carrier with an acid salt solution containing rare earth elements to obtain a suspension;

b) precipitating the rare earth elements in the suspension with an alkaline substance to obtain a carbon carrier composited with hydroxides of the rare earth elements;

c) sintering the carbon carrier composited with the hydroxide of the rare earth element to obtain a composite carrier;

d) mixing the precursor of the noble metal with the composite carrier, and microwave sintering to obtain the fuel cell catalyst.

Preferably, the acid salts of rare earth oxides are nitrates, sulfates or hydrochlorides of rare earth elements.

Preferably, the precursor of the noble metal is H ₄ PtCl ₆ , PtCl ₄ , PtCl ₂ (NH ₃ ) ₂ , _{H 4} PdCl 6 , PdCl ₄ , PdCl ₂ (NH ₃ ) ₂ , H ₄ AuCl ₆ , AuCl ₄ , AuCl ₂ (NH ₃ ) ₂ .

Preferably, the carbon support is carbon nanotube, activated carbon, carbon fiber, graphene or carbon gel.

Preferably, step a) specifically includes: a1) dissolving rare earth oxides in concentrated nitric acid to obtain an acid salt solution containing rare earth elements;

a2) Dilute the acid salt solution with 1:1 ethanol and secondary water;

a3) Mixing the carbon support with the acid salt solution to obtain a suspension.

Preferably, step d) is specifically:

d1) mixing and dispersing the composite carrier and the noble metal precursor of the noble metal in ethylene glycol to obtain an ethylene glycol suspension

d2) adjusting the pH value of the ethylene glycol suspension to 10.5-11.5;

d3) Microwave sintering the alkaline ethylene glycol suspension obtained in step d2) for 30-180 s, and filtering to remove the filtrate to obtain a fuel cell catalyst.

The catalyst provided by the invention is obtained by doping a carbon carrier with a rare earth oxide and then loading a noble metal. The noble metal has high catalytic activity, and the carbon carrier has good conductivity and surface area. affinity, so it is not easy to peel off after being loaded, and it will not lose its activity due to long-term use. In addition, the rare earth oxide itself has very rich outer electrons and can provide oxygen-containing groups, which are compatible with the active component of the catalyst. The combination can provide the electrocatalytic activity of the catalyst; the most important thing is that the rare earth oxide in the catalyst provided by the invention can accelerate the decomposition and adsorption of the intermediate product of the fuel cell reaction through the electronic effect and the dual function mechanism, thereby improving the anti-poisoning ability of the catalyst. The catalyst provided by the invention can be used in catalytic reactions of direct methanol fuel cells, direct formic acid fuel cells and direct ethanol fuel cells.

The invention provides a preparation method of a fuel cell catalyst, comprising: a) mixing a carbon carrier with an acidic salt solution containing a rare earth element to obtain a suspension; b) precipitating the rare earth element in the suspension with an alkaline substance , to obtain a carbon carrier composited with a hydroxide of a rare earth element; c) sintering the carbon carrier composited with a hydroxide of a rare earth element to obtain a composite carrier; d) mixing a precursor of a noble metal with the composite carrier, and microwave sintering A fuel cell catalyst is obtained. The process of the preparation method provided by the invention is simple and controllable, can firmly combine the carbon carrier, the rare earth oxide and the precious metal, and the obtained catalyst has good poisoning resistance.

Description of drawings

Figure 1 is the XRD pattern of the catalyst and _Eu2O3 /C support provided by Example 1 of the present _invention ;

Fig. 2 is the EDX diagram of PdEu ₂ O ₃ /C provided by Example 2 of the present invention;

_Figure 3 is the XRD pattern of Pd _Ce2O3 /C and _Ce2O3C carriers provided by Example 3 of _the present invention;

Fig. 4 is a TEM image of the PbYb ₂ O ₃ /C catalyst provided by Example 4 of the present invention.

Detailed ways

In order to further understand the present invention, the preferred embodiments of the present invention are described below in conjunction with the examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention rather than limiting the patent requirements of the present invention.

The invention provides a fuel cell catalyst. include,

Composite carrier. Prepared from rare earth oxides and carbon supports;

Noble metals are loaded on the composite carrier.

In order to provide a catalyst with high ability to resist poisoning by intermediate products, the present invention dopes the carbon carrier with rare earth oxides. Since rare earth oxides have abundant outer electrons and can provide oxygen-containing groups, they can improve the catalytic ability of catalyst active components through electronic effects and dual-functional mechanisms; the presence of rare earth oxides can also accelerate the decomposition and adsorption of fuel cells Toxic compounds are produced, thereby improving the performance of the battery.

According to the present invention, the rare earth oxides are preferably oxides of 15 lanthanide elements with atomic numbers from 57 to 71 and seventeen elements including scandium and yttrium. The carbon support is preferably carbon nanotubes, activated carbon, carbon fibers, graphene or carbon gel. According to the present invention, the noble metal includes: one or more of Pt, Pd, Au, Ir, Ru, Rh, Ag, Os, more preferably Pt, Pd, Au or PtPd, PtRu, PtIr, PtPdAu , PtRuOs, most preferably Pt, Pd.

Rare earth oxide and carbon composite support (ReO/C) supported catalysts can be used in the following direct liquid fuel cells including direct methanol fuel cells, direct formic acid fuel cells, direct ethanol fuel cells, etc. The catalyst that has catalytic activity to the anode fuel can be used as the anode catalyst of the fuel cell, and the catalyst that has catalytic activity to the cathode oxygen reduction can be used as the cathode catalyst; some catalysts have catalytic activity to the anode fuel and can also reduce the anode oxygen. It has catalytic activity, so it can be used as an anode catalyst or as a cathode catalyst.

The present invention also provides a preparation method of fuel catalyst, comprising:

a) mixing the carbon carrier with an acid salt solution containing rare earth elements to obtain a suspension;

b) precipitating the rare earth elements in the suspension with an alkaline substance to obtain a carbon carrier composited with hydroxides of the rare earth elements;

c) sintering the carbon carrier composited with the hydroxide of the rare earth element to obtain a composite carrier;

d) mixing the precursor of the noble metal with the composite carrier, and microwave sintering to obtain the fuel cell catalyst.

According to the present invention, at first prepare the acidic salt solution containing rare earth element,

a1) dissolving rare earth oxides in concentrated nitric acid to obtain an acid salt solution containing rare earth elements;

a2) carrying out the acid salt solution with 1:1 ethanol and secondary water;

a3) Mixing the carbon support with the acid salt solution to obtain a suspension.

The rare earth oxide (ReO) was dissolved in concentrated nitric acid, and then diluted with 1:1 ethanol and secondary water. The carbon carrier was added to the above solution for ultrasonic treatment and sufficient mechanical stirring to obtain a suspension.

Sodium carbonate and sodium hydroxide were then added to the above suspension to form a precipitate of ReO. Finally, the above suspension was filtered, washed, and the solid matter was transferred to a tube furnace for thermal decomposition treatment under the protection of nitrogen to obtain a stable ReO/C composite support. According to the present invention, the molar ratio of the rare earth oxide (ReO) to concentrated nitric acid is 1:1-10, more preferably 1:2-8, and most preferably 1:4-6. Use 1:1 ethanol and secondary water to dilute, and add the 1:1 ethanol and secondary water diluted at least 3 times, that is to say more than 3 times, into the above solution. The mass of the carbon support accounts for 0.1wt%-99.9wt% of the mass of the ReO/C composite support, more preferably 10wt%-80wt%, most preferably 25wt%-60wt%.

Ultrasonic treatment and sufficient mechanical stirring, that is, the ultrasonic time is not less than half an hour, and the mechanical stirring is not less than 1 hour.

Preferably, the mass ratio of the sodium carbonate to the rare earth oxide is 1:0.1-0.3. Sodium hydroxide can ensure that the pH of the solution is >9.

According to the present invention, the sintering temperature is preferably 450-600°C, more preferably 500-550°C.

After the ReO/C composite carrier is prepared, the precious metal is loaded on the composite carrier. The preparation method is as follows:

d1) mixing and dispersing the composite carrier and the noble metal precursor of the noble metal in ethylene glycol to obtain an ethylene glycol suspension

d2) adjusting the pH value of the ethylene glycol suspension to 10.5-11.5;

d3) Microwave sintering the alkaline ethylene glycol suspension obtained in step d2) for 30-180 s, and filtering to remove the filtrate to obtain a fuel cell catalyst.

The composite carrier and the noble metal precursor are dispersed in a certain amount of ethylene glycol under ultrasonic conditions for thorough mixing, and then the pH value is adjusted to 10.5-11.5 with sodium hydroxide solution. Then the ethylene glycol suspension after the adjusted pH value is placed in a microwave oven for microwave sintering, wait for the temperature to drop to room temperature, filter the ethylene glycol suspension, wash, and dry the solid matter in a drying oven. A noble metal catalyst supported by ReO/C was obtained.

According to the present invention, the mass of the noble metal precursor accounts for 1 to 80 wt% of the total mass of the composite carrier and the noble metal precursor; the noble metal precursor is preferably a noble metal salt, such as H ₄ PtCl ₆ , PtCl ₄ , PtCl ₂ (NH ₃ ) ₂ , H ₄ PdCl ₆ , PdCl ₄ , PdCl ₂ (NH ₃ ) ₂ , H ₄ AuCl ₆ , AuCl ₄ , AuCl ₂ (NH ₃ ) ₂ .

The concentration of the sodium hydroxide used to load the noble metal is 1-2M, and the sodium hydroxide solution is required to be added dropwise in the said ethylene glycol suspension.

According to the present invention, the microwave sintering time is preferably 30-180s; if the heating time is longer than 1 minute, intermittent heating is required, such as heating for 1 minute and stopping for 10s-30s.

Below are specific embodiments of the present invention, set forth in detail the technical scheme of the present invention:

Example 1

ReO takes Eu ₂ O ₃ rare earth oxide as an example and Pd as the noble metal, where the mass content of Pd and rare earth oxide in PdEuO/C is 20% and 15% for illustration.

Weigh 20 mg of rare earth oxide (Eu ₂ O ₃ ) and dissolve it in 10 ml of concentrated nitric acid, and then use 40 ml of 1:1 ethanol and secondary water to dilute. Add 80mg of activated carbon to the above solution for half an hour of ultrasonic treatment and 2 hours of mechanical stirring, then add 100ml of 1M sodium carbonate solution and 10mL of 1M sodium hydroxide to the above solution to form Eu ₂ O ₃ precipitation. Finally, the above mixed solution is filtered and washed, and the solid matter is transferred to a tube furnace for thermal decomposition at a certain temperature under the protection of nitrogen to obtain a stable Eu ₂ O ₃ /C composite carrier. Disperse 80 mg of the composite carrier obtained above and a certain amount of noble metal precursor H ₂ PdCl ₆ (containing 20 mg Pd) into 50 ml of ethylene glycol under ultrasonic conditions for thorough mixing, and then use 1M sodium hydroxide solution to adjust the pH value to about 11. Then place the mixed solution in a microwave oven for a certain period of time, wait for the temperature to drop to room temperature, filter the mixed solution, wash, and dry the solid matter in a drying oven at 80°C to obtain PdEu ₂ O ₃ /C catalyst. Figure 1 is the XRD pattern of the catalyst and Eu ₂ O ₃ /C carrier. It can be seen from the figure that the diffraction peak of Eu ₂ O ₃ can be seen on the Eu ₂ O ₃ /C carrier. Pd diffraction peaks can be seen in PdEu ₂ O ₃ /C catalyst. Figure 2 is the EDX diagram of PdEu ₂ O ₃ /C, from which the obvious peaks of Pd, Eu and O can be seen, thus proving the existence of Pd and Eu ₂ O ₃ .

Example 2

ReO takes Ce ₂ O ₃ rare earth oxide as an example, uses Pd as the noble metal, and its content and preparation method are the same as above.

Figure 3 is the XRD patterns of Pd Ce ₂ O ₃ /C and Ce ₂ O ₃ C carriers, from which it can be seen that the diffraction peaks of Ce ₂ O ₃ and Pd exist.

Example 3

ReO takes Yb ₂ O ₃ rare earth oxide as an example, uses Pt as noble metal, and its content and preparation method are the same as above.

Fig. 4 is a TEM image of the PbYb ₂ O ₃ /C catalyst, from which it can be seen that Pb nanoparticles are uniformly dispersed on the carbon support.

A fuel cell catalyst provided by the present invention and its preparation method have been described in detail above. The principles and implementation methods of the present invention have been explained by using specific examples in this paper. The descriptions of the above examples are only used to help understand the present invention. method and its core idea, it should be pointed out that for those of ordinary skill in the art, without departing from the principles of the present invention, some improvements and modifications can also be made to the present invention, and these improvements and modifications also fall into the scope of the present invention within the scope of the claims.

Claims (10)

1. A fuel cell catalyst, characterized in that, comprising, Composite carrier. Prepared from rare earth oxides and carbon supports; Noble metals are loaded on the composite carrier. 2 . The catalyst according to claim 1 , wherein the rare earth oxides are oxides of 15 lanthanide elements with atomic numbers from 57 to 71 and seventeen elements including scandium and yttrium. 3. The catalyst according to claim 1, wherein the noble metal is one or more of Pt, Pd, Au, Ir, Ru, Rh, Ag and Os, 4. The catalyst according to claim 1, characterized in that, the carbon carrier is carbon nanotube, activated carbon, carbon fiber, graphene or carbon gel. 5. A preparation method of a fuel cell catalyst, characterized in that, comprising: a) mixing the carbon carrier with an acid salt solution containing rare earth elements to obtain a suspension; b) precipitating the rare earth elements in the suspension with an alkaline substance to obtain a carbon carrier composited with hydroxides of the rare earth elements; c) sintering the carbon carrier composited with the hydroxide of the rare earth element to obtain a composite carrier; d) mixing the precursor of the noble metal with the composite carrier, and microwave sintering to obtain the fuel cell catalyst. 6. The catalyst according to claim 5, characterized in that, the acid salt of the rare earth oxide is a nitrate, sulfate or hydrochloride of a rare earth element. 7. The catalyst according to claim 5, wherein the precursor of the noble metal is H ₄ PtCl ₆ , PtCl ₄ , PtCl ₂ (NH ₃ ) ₂ , H ₄ PdCl ₆ , PdCl ₄ , PdCl ₂ (NH ₃ ) ₂ , H ₄ AuCl ₆ , AuCl ₄ , AuCl ₂ (NH ₃ ) ₂ . 8. The catalyst according to claim 5, characterized in that, the carbon carrier is carbon nanotube, activated carbon, carbon fiber, graphene or carbon gel. 9. The preparation method according to claim 5, wherein step a) is specifically: a1) dissolving rare earth oxides in concentrated nitric acid to obtain an acidic salt solution containing rare earth elements; a2) Dilute the acid salt solution with 1:1 ethanol and secondary water; a3) Mixing the carbon support with the acid salt solution to obtain a suspension. 10. The preparation method according to claim 1, characterized in that step d) is specifically: d1) mixing and dispersing the composite carrier and the noble metal precursor of the noble metal in ethylene glycol to obtain an ethylene glycol suspension d2) adjusting the pH value of the ethylene glycol suspension to 10.5-11.5; d3) Microwave sintering the alkaline ethylene glycol suspension obtained in step d2) for 30-180 s, and filtering to remove the filtrate to obtain a fuel cell catalyst.

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