Tungsten Oxide Photocatalytic Principle

Photo-driven photocatalytic reaction is considered as one of the most promising strategies to solve the current energy and environmental problems. Photocatalytic technology is a synthesis of light and catalytic words, refers to the presence of light and catalyst in the chemical reaction. When used as a photocatalyst, tungsten oxide can not only degrade various organic pollutants, but also can be used for water oxidation, pyrolysis water and carbon dioxide reduction.

Tungsten oxide photocatalytic material from the energy band consists of three parts: the electron-filled low-energy band, the empty high-energy conduction band and the conduction band and valence band formed between the band gap. Under light irradiation, the energy absorbed by the tungsten oxide photocatalytic material is greater than or equal to the energy of the bandgap, the electrons in the valence band are excited to transition to the conduction band to form photogenerated electrons while an empty valence band is formed hole. This creates a photogenerated electron-hole pair.

The resulting photogenerated electron and hole pairs move toward the surface of the material due to the force of the electric field. During the moving process, the following four situations occur:
(A) Photons and holes recombine after moving to the surface of the material.
(B) Photo-generated electrons and holes recombined without moving to the surface of the material.
(C) The photogenerated electrons move to the surface of the material to react with dissolved oxygen adsorbed on the surface to form strongly oxidizing species.
(D) Holes moving to the surface of the material react with water and hydroxyl groups in the solution to form hydroxyl radicals. Generated strong oxidizing species can be directly degraded pollutants, water splitting and reduction of carbon dioxide.

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