Photoinduced Charge Modulation And Properties Of Multiphase TiO₂ Photocatalytic Materials

Semiconductor catalytic materials have broad application in solving current global environmental problems and energy crisis.TiO₂,as a traditional semiconductor photocatalytic material,has been widely used due to its stable chemical properties,no pollution and low cost.However,it is an urgent problem to improve visible light utilization and promote photogenic charge separation.In this paper,the catalytic and photoelectrochemical properties of multiphase TiO₂ are improved through the regulation of photogenic charge.From regulating phase ratio of single TiO₂ photocatalytic to the design of composite materials,charge dynamics process is explored.Specifically,the enhanced light response ability is benefit from element doping and structure regulation.The construction of multiphase TiO₂-TiO₂ nanotubes homogeneous and the electric field action generated by the spontaneous polarization of ferroelectric materials can realize the effective separation and utilization of photogenerated charge.The main results are as following:?1?A series of mixed-phases TiO₂?anatase/rutile,anatase/rutile/brookite,anatase/brookite?were prepared by hydrothermal process.Phase composition and content of TiO₂ were determined by XRD.Besides,the morphology and structure were further characterized by SEM and TEM.The results confirm that the phase composition is closely related to ammonia concentration.When the amount of NH₃·H₂O in the reaction medium increases to 4 m L,the mix phase TiO₂(A₆₁B₃₉)with the most compact interface structure and the maximum specific surface area can be obtained.Compared with triphase TiO2,A₆₁B₃₉ with suitable band structure and quantum size brookite is benefit the charge separation and transfer.Especially,the hightest degradation ration of LVFX reached 73%after 100 min under visible light irradiation.?2?N/Ti³⁺co-doped triphase TiO₂-TiO₂ nanotube arrays?3Ph NT?TNT??was constructed by hydrothermal reaction of Ti N and TiO₂ nanotube arrays.The crystal structure,morphology,and composition of the as-prepared samples were investigated.It was found that N/Ti³⁺co-doped triphase TiO₂ nanoparticles were uniformly deposited on TiO₂ nanotube arrays.The band gap narrowing of as-prepared samples could be attributed to the N and Ti³⁺codoping in N/Ti³⁺codoped triphasic TiO₂ layer.Meanwhile,the construction of triphase TiO₂-TiO₂ nanotubes homogeneous is beneficial to the separation of photogenic charges.The results indicated that 3Ph NT?TNT?showed improved photoelectrochemical performance compared with TNT.Especially,the 3Ph NT?TNT?-25exhibited more photogenic carriers,enhanced photoconversion efficiency and photoelectrochemical properties.?3?Bi_0.5Na_0.5TiO₃nanoparticles used in this work were synthesized by hydrothermal method.Titanium oxide?TiO₂?was used as titanium precursor,bismuth nitrate pentahydrate?Bi?NO₃?₃·5H₂O?as bismuth precursor and sodium hydroxide?Na OH?as sodium precursor and mineralizer.Then,multiphase TiO₂/Bi_0.5Na_0.5TiO₃ heterojunctions were synthesized using a simple ultrasonic irradiation method.The phase composition and morphology of samples were characterized by XRD,SEM and TEM.The interfacial effect existed between TiO₂?anatase?and Bi_0.5Na_0.5TiO₃.Interestingly,XPS indicates that the unique architecture could effectively facilitate the separation and transfer of photo-induced electron from TiO₂ to Bi_0.5Na_0.5TiO₃.What's more,the electric field action generated by the spontaneous polarization of ferroelectric materials can inhibit the photo-generated charge recombination.Therefore,the obtained heterojunctions as the sonocatalyst afford excellent photoelectrochemical and ultrasonic catalytic performance.