Construction And Properties Of Long Afterglow Composite Photocatalytic Materials With Visible Light Response

With the global shortage of fossil energy and the deterioration of environmental pollution,photocatalysis,as one of the clean and efficient solar energy utilization technology,has received unprecedented attention.The use of semiconductor photocatalyst to convert solar energy into chemical energy and activate the chemical reaction has great potential in hydrogen production from photocatalytic water splitting,water pollution treatment,and other aspects.However,the photocatalytic reaction needs a light source to drive,which limits its application in the dark or sewage treatment with a light-shielding effect.Long persistent phosphors（LPPs）are a type of energy storage material with unique luminescent properties,which can keep glowing for several seconds to several hours after the external excitation stops.Benefitting from the above characteristics,LPPs are very suitable as internal spontaneous light sources of photocatalyst for initiating photocatalytic reactions in the dark.Therefore,it is a feasible strategy to effectively drive photocatalytic reactions in the dark by modifying TiO₂ photocatalyst to broaden its light response range as well as providing a continuous internal light source for photocatalyst by compounding with LPPs,which is of great significance in the construction of a round-the-clock photocatalytic system.Inspired by the above-mentioned ideas,this work firstly designed and synthesized TiO₂ photocatalyst with a visible light response and Zn₂SiO₄:Ga³⁺,Bi³⁺LPPs with blue and ultra-violet emission.Then,the composite material of TiO₂and Zn₂SiO₄:Ga³⁺,Bi³⁺with a close contact interface and good spectral band overlap was synthesized,and its application prospect in photocatalytic degradation of pollutants in water was explored.The main works are summarized as follows:（1）The Co,Ni,and Cr ions doping TiO₂ photocatalysts M-TiO₂ were synthesized by the sol-gel method,and the surface properties,band structure,and optical responsiveness of TiO₂ before and after doping were studied.Furthermore,the photocatalytic performance of M-TiO₂ with visible light response was investigated by degradation of pollution markers.（2）The LPPs with different compositions and different concentrations of doped ions were synthesized by the high-temperature solid-state method and the relationship between luminescence properties and the concentration of doped ions was studied.On this basis,a single doped Zn₂SiO₄:Ga³⁺material with proper luminescence intensity and afterglow lifetime was obtained.Then,through Bi³⁺co-doping,the emission of dual-doped Zn₂SiO₄:Ga³⁺,Bi³⁺was adjusted to make it have ultraviolet luminescence.（3）Based on the above two modified materials,a simple sol-gel method was used to prepare M-TiO₂ coated Zn₂SiO₄:Ga³⁺,Bi³⁺LPPs.Then,the photocatalytic performance of M-TiO₂@Zn₂SiO₄:Ga³⁺,Bi³⁺composites was studied by degradation of pollution markers.