Semiconductor TiO2 and transition metal oxides, layered metal compounds, such as K4Nb6O17, K2La2TiO10, Sr2Ta2O7, etc., as well as catalytic materials that can use visible light, such as CdS, Cu-ZnS , etc., can be used in certain lighting conditions. It splits water catalytically to produce hydrogen. However, so far, the efficiency of photocatalytic water splitting is still very low, only 1-2%. The redox catalytic systems used for water photolysis that have been studied mainly include semiconductor systems and metal complex systems, among which the semiconductor system has been studied the most. Semiconductor photocatalysis is similar in principle to a photoelectrochemical cell. Small photo-semiconductor particles can be considered as microelectrodes suspended in water. The difference is that there is nodifference between them like photoelectrochemical cells. , and even the cathodes are envisioned as being on the same particle, with the reaction of water splitting into hydrogen and oxygen occurring simultaneously. When ultraviolet light below 387 nm irradiates TiO2, the electrons in the valence band absorb energy, and the transition to the conduction band is generated in the valence band and conduction band respectively, and the molecules of water adsorbed on TiO2 are strongly oxidized. the holes are oxidized to oxygen and the hydrogen ions generated at the same time are reduced to hydrogen gas by the electrons after migrating into the electrolyte. Compared with photoelectrochemical cells, the photocatalytic decomposition reaction of semiconductor water to release hydrogen is greatly simplified, but the electron-hole pairs generated on the same semiconductor particle by light excitation areeasily recombined. Therefore, in order to suppress the reverse reaction of hydrogen and oxygen and the recombination of electrons and holes generated by light-excited semiconductors, electron donors can be added as hole trappers to improve the efficiency of hydrogen release. Many organic materials found in wastewater are good electron donors. If wastewater treatment is combined with photocatalytic hydrogen production, solar hydrogen production and solar decontamination can be realized at the same time.
Yes. Experiments show that after a certain period of using photocatalytic materials, the reaction activity will gradually decrease, resulting in a decrease in hydrogen production, mainly because the catalytic materials are also affected by external factors such as l oxygen and water when they arent exposed. light, which leads to a change in the physical and chemical properties of the material surface and a reduction in catalytic activity. Photocatalytic hydrogen production is a technology that uses solar energy and photocatalytic materials to promote the splitting of water to produce hydrogen.