Research On The Mechanism Of Photoelectron Transfer In Titanium Dioxide

The treatment of industrial dyeing wastewater is gradually transformed from adsorption to environmental protection and stable treatment.This is precisely met by the photocatalytic advanced oxidation method.Photocatalyst absorbs organic pollutants and generates active substances through solar irradiation to destroy the structure of organic matter,and finally mineralizes into CO₂ and H₂O.The key to improve the photocatalytic degradation ability is to prolong the activity of free radicals in photocatalysis,usually by delaying the recombination time of photogenerated electron/hole pairs.In this paper,three different photoelectron transport carriers were constructed to effectively transfer the photoelectrons of TiO₂ to improve the photocatalytic activity.The cation filling method is used to drive TiO₂ to be dispersed on the surface of MMT.After MMT transfers TiO₂ photoelectrons,it can directly use hydrophilicity to preferentially drive O₂ to combine with the migrating photoelectrons to generate O₂^-.At the same time,the MMT’s own electric field interferes with the growth of TiO₂ loaded on its surface,controlling the formation of smaller particle sizes and more oxygen vacancies,providing support for photocatalytic active sites and the number of surface free electrons.Although MMT has excellent ability to transmit photoelectrons,it is not a semiconductor material and does not have photocatalytic performance.Therefore,Bi₂Ti₂O₇ is chosen as a carrier to construct a TiO₂-Bi₂Ti₂O₇ Z-scheme heterojunction.Bi OI and TiO₂ hydrosol synthesized in water phase are used as precursors.By controlling the ratio of precursors and heat treatment temperature,a Z-scheme heterojunction with homogeneous growth of Bi₂Ti₂O₇ double-crystalline phase TiO₂ on the surface is obtained.Both rutile and anatase TiO₂ and Bi₂Ti₂O₇ form a Z-scheme heterojunction.The presence of oxygen vacancies in the Bi-O structural unit in Bi₂Ti₂O₇ provides a limiting point for photoelectrons migrated from TiO₂.Based on first-principles calculations,the increase in the density of states of Bi atoms and the shift of the valence band to higher energy levels by oxygen vacancies help to form a stronger confinement effect.Building a multi-migration photoelectron transmission path based on the Z-scheme heterojunction will obtain more excellent photocatalytic performance.Therefore,a TiO₂-Co OOH photocatalyst was constructed with cobalt nitrate as the precursor.The multi-layer electron free transport performance of Co OOH is based on the Z-scheme heterojunction of TiO₂and Co OOH,which continuously extends the migration distance and photo-generated electrons/holes.Compound time.At the same time,Ca₉Co₁₂O₂₈ interferes significantly with the growth of TiO₂,and the oxygen vacancy ratio reaches 20%,and it attracts more free electrons to be adsorbed on the surface of TiO₂.The oxygen vacancies in Co OOH make the photoelectrons migrated by TiO₂ more firmly stored in the Co OOH sheet.In the lamellae,it gradually generates active free radicals with O₂ and other substances along with the transition.First-principles calculations show that the presence of oxygen vacancies and Ca²⁺in Co OOH both enhance the band gap and the ability to transmit photoelectrons.The three chapters of the experiment content gradually improve the photoelectron migration path of TiO₂ and provide reference for subsequent researchers in extending the recombination rate of photogenerated electrons/holes in TiO₂.