Tungsten Carbide-Platinum Composite Catalyst Applied In Fuel Cell

The fuel cell is a proton exchange membrane fuel cell. It directly uses methanol aqueous solution or hydrogen as a fuel supply source to generate electricity. It has the characteristics of quick start at low temperature, environmental friendliness, and simple battery structure. It is an efficient green energy source.

Most of the existing fuel cell technologies use carbon black as a carrier to load Pt particles onto the surface of carbon black to obtain a supported Pt/C catalyst. The carbon carrier has a large specific surface area, which can greatly reduce the amount of precious metal Pt used and reduce the overall cost of the battery. However, its problem of oxidative sintering is also an important problem that plagues researchers.

The fuel cell has a unique working environment inside, with high temperature (50-90 ° C), high water content, high acidity (pH < 1) and high potential (0.6-1.2 V). Under such harsh conditions, and under long-term conditions, electrochemical oxidation of carbon is more likely to occur, especially at high Pt levels. Moreover, when the battery is operated under unconventional conditions, such as poor start-up or load change, a reverse polarity condition may occur, which may cause an irreversible effect on the battery due to extreme oxidation of carbon.

In many years of research, it has been found that tungsten carbide has catalytic properties similar to platinum. Some scholars have used tungsten carbide instead of carbon black to prepare a tungsten carbide-platinum composite catalytic material that can be used in fuel cells. The synthesis scheme of this material is as follows:

Step (1), weigh 1g Vulcan XC-72 carbon powder, put into 32% HNO3 solution, heat reflux for 1 hour, filter, wash with deionized water to pH = 6.5, 110 ° C constant temperature drying;

Step (2), the Vulcan XC-72 carbon powder treated in the step (1) is placed in a three-necked flask, isopropanol and water are added, and then the H2WO4 solution is added. The molar ratio of carbon to tungsten is 1:1, and the ultrasonic wave is thoroughly mixed. Uniform, add hydrogen peroxide and ammonia to adjust pH = 6.5, and let stand for 5 hours;

Step (3), under the N2 protection and ultrasonic stirring conditions, the excess NaBH4 solution is added dropwise to carry out the reduction reaction; after the reaction is completed, it is subjected to suction filtration, washing, and vacuum drying at 80 ° C for 4 hours;

Step (4) The product was placed in a tube furnace, calcined under a mixed atmosphere of N2 and H2, calcined at 800 ° C for 2.5 hours, and calcined at 1150 ° C for 3.5 hours to obtain a tungsten carbide powder material.

Step (5), the tungsten carbide powder material obtained in the step (4) is placed in a three-necked flask, and then anhydrous ethanol, water and isopropanol are sequentially added, ultrasonically mixed uniformly, and ultrasonically stirred for 10 minutes by adding 10 mg/mL H2PtCl6 solution, using 1 mol. /L Na2CO3 solution adjusted to pH = 7, and allowed to stand for 12h, to obtain a mixed slurry containing tungsten carbide material;

Step (6), slowly adding 37% formaldehyde solution to the slurry, the temperature is controlled at 65 ° C, the reaction is carried out with nitrogen as a shielding gas, ultrasonic stirring, after the reaction is completed, the aeration is stopped, vacuum filtration, washing with deionized water to Without Cl-, the filter cake was dried under vacuum at 80 ° C to obtain a tungsten carbide-platinum composite catalyst.

The tungsten carbide-platinum composite catalytic material was prepared into an electrode and constituted a battery, and compared with a single cell using conventional carbon-supported platinum as a catalyst, and the performance after oxidation at 1.8 V was compared. The decay of the tungsten carbide-platinum catalyst was significantly lower than that of the Pt/C battery at each electrical density, which proved that the novel composite catalyst has better oxidizing environment tolerance.

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