Bismuth - Bismuth Tungstate Ternary Composite Photocatalyst

As photochemical smog, acid rain and ozone layer destruction pollutants, nitrogen oxides have become an urgent air pollutant in the world. As an environmentally friendly green technology, visible light-driven photocatalysis has shown a good application prospect in environmental pollution purification and solar energy conversion.

Visible light-driven photocatalytic method can make nitrogen oxides oxidize under the action of photocatalysis, and produce H₂O, nitrate, nitrite and so on, so as to achieve harmless, thereby purifying the environment. In 1999, Kudo first reported that bismuth tungstate has the activity of photocatalytic decomposition of water, which has aroused close research in environmental protection science. The results show that bismuth tungstate has strong photocatalytic activity for the mineralization of CHCl₃ and CH₃CHO. However, the bismuth photocatalysts prepared by the existing preparation methods of bismuth-based photocatalysts have narrow light response range, low solar energy utilization rate, serious photogenerated electrons and hole recombination, which hinder the application of bismuth-based photocatalytic technology. Therefore, it is urgent to find a preparation method of bismuth photocatalyst with high solar energy utilization and stable photocatalytic performance.

Some scholars have developed a bismuth-amorphous strontium tungstate-bismuth trioxide ternary organic composite photocatalyst, which can solve the shortcomings of the quinone-based photocatalyst described in the background art, and the preparation process includes the following contents:

1.Bismuth solution is obtained by dissolving the precursor of bismuth in deionized water, and tungstate solution is obtained by dissolving the precursor of tungstate in deionized water.

2.The bismuth solution is uniformly matched with the tungstate solution, and the amorphous bismuth tungstate powder is obtained by constant temperature reaction in the oven.

3.Bismuth-amorphous bismuth tungstate-bismuth trioxide ternary organic composite photocatalyst was synthesized by in-situ deposition method by dissolving the reductant and the amorphous bismuth tungstate powder in deionized water and mixing at room temperature.

The existence of Bi nanoparticles can enhance the visible photocatalytic activity of amorphous bismuth tungstate. There are several reasons. First, the strong surface plasmon effect of Bi nanoparticles can make amorphous bismuth tungstate absorb more visible light. Second, surface plasmon can promote the electron excitation and transfer of Bi nanoparticles. The Fermi level of Bi is - 0.17eV, which is more negative than the conduction level of Bi tungstate is 0.46eV. It is beneficial to the transfer of photogenerated electrons from Bi to amorphous Bi tungstate.

At the same time, photogenerated electrons transfer from the conduction band of Bi2O₃ (0.33 eV) to the conduction band of amorphous bismuth tungstate (0.46 eV), and photogenerated holes transfer from the valence band of amorphous bismuth tungstate (3.26 eV) to the valence band of Bi2O₃ (3.13 eV). This can effectively reduce the recombination of photogenerated electrons and hole pairs, and more photogenerated electrons can be used to reduce the formation of O₂^-. At the same time, compared with the semi-metal-organic composite photocatalyst formed by noble metal supported on the surface of bismuth tungstate, the bismuth-amorphous bismuth tungstate-bismuth trioxide ternary organic composite photocatalyst is cheap, easy to prepare and can be better used in the field of photocatalysis.

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