Optimum Cocatalyst-Tungsten Carbide

Since the discovery of platinum-like catalytic performance by American scientists in the last century, tungsten carbide has been found to have high catalytic or catalytic activity in hydrocarbon reforming, decomposition, hydrogenation, isomerization, electrochemical oxidation of hydrogen and alcohols, and electrochemical reduction of oxygen.

In the field of fuel cells, tungsten carbide supported platinum (Pt/WC) as catalyst for methanol oxidation and oxygen reduction has lower overpotential and higher current density than commercial platinum/carbon (Pt/C) catalyst. Moreover, with the increase of the specific surface area of tungsten carbide, the catalytic activity of tungsten carbide on the catalyst is enhanced. In addition, tungsten carbide as catalyst carrier can protect active components from CO poisoning.

However, the precondition of tungsten carbide as a catalyst is how to reduce the particle size of tungsten carbide or improve the surface area of tungsten carbide materials, which is very important for its role as a catalyst promoter. Some researchers wrapped the carbon precursor and tungsten precursor on the template by hydrothermal method, then removed the template by high temperature decomposition, and decomposed the tungsten precursor into tungsten oxide. Finally, tungsten carbide with hollow hemisphere structure was prepared by high temperature treatment under nitrogen protection. The experimental process is roughly as follows:

In a high pressure reactor with 50 mL lined polytetrafluoroethylene gallbladder, 1 g of polystyrene ball with 1.3 micron diameter, 2 g of glucose, 1 g of ammonium tungstate and 40 ml of deionized water were added to mix evenly. Seal the autoclave and place it in the oven. Heat it up to 180 ℃ for 12 hours. After cooling, the solid powder was dried and heated for 2 minutes in a microwave oven with a power of 2000 W. The hollow tungsten carbide hemisphere with a diameter of 1.6 micron and a wall thickness of about 200 nanometers was obtained by placing the product in a tubular furnace and holding it at 900 ℃ for 2 hours under the protection of nitrogen. The hollow tungsten carbide hemisphere has regular appearance and uniform particle size.

Under the conditions of 0.1 mol/L perchloric acid in electrolyte, 25 ℃, 5 mV/s scanning speed and 1600 RPM electrode speed, the oxygen reduction performance of supported Pt catalyst (Pt/WC hollow hemisphere) was compared with that of traditional Pt/C catalyst. The results showed that WC hollow hemisphere as support had a significant catalytic effect on Pt catalyst. The hollow hemisphere of tungsten carbide can greatly improve the activity of Pt catalyst and reduce the overpotential of the reaction.

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