Hydrogen Reduces Tungsten Oxide Defects

High-temperature annealing in a hydrogen atmosphere is an effective way to obtain a non-stoichiometric tungsten oxide structure containing oxygen vacancies. However, it should be noted that hydrogen is a flammable and explosive gas, which is more likely to explode at high temperatures. The high temperature conditions are indispensable, it played to overcome the activation energy barrier.

Due to the great danger of using tungsten oxide to reduce tungsten oxide at high temperatures, it is necessary to use a reducing agent with a low risk factor to reduce tungsten oxide instead of hydrogen. Some inorganic hydrides such as sodium cyanide, calcium hydride and so on. Oxygen vacancies can also be introduced into semiconductor materials by reduction reactions. Due to their high reductive activity, these inorganic hydrides can provide hydrogen ions to reduce oxygen in the semiconductor material by solid reaction to generate oxygen vacancies in the structure thereof. These inorganic hydrides have high reducing activity and are not easily detonated at high temperatures and therefore can be used as a reducing agent to reduce tungsten oxide to obtain a sub-stoichiometric tungsten oxide structure.

Hydrogenation of tungsten oxide using a sodium borohydride with a strong reduction selectivity instead of hydrogen as a reducing agent is an effective method. Tungsten oxide and sodium borohydride are milled and mixed to reduce tungsten oxide by a solid reaction to introduce oxygen vacancies therein. Through the SEM, XRD and XPS characterization methods, we can explore the effect of different annealing temperature on the formation of oxygen vacancies and tungsten oxide morphology and structure changes. After that, the plasma resonance effect of the hydrogenated sample was observed. Finally, the electrocatalytic hydrogen evolution activity of different samples was analyzed by Tafel slope and EIS, and the influence of hydrogenation on the electrocatalytic activity was also investigated.

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