Design And Synthesis For Micro-nano Metal Oxide Composites And Their Photocatalytic Applications

Photocatalysis,as a new environmental-friendly technology,was widely used in photoelectric fields.The traditional photocatalysts often present advantages of low price,simple preparation and great industry demands,while showed poor responsiveness under visible light irradiation.It is necessary to construct more composite materials with improved photocatalytic performance.However,there were some problems for photocatalysts,such as low precision of active centers,poor stability and so on.As a result,a series of micro-nano hierarchical photocatalytic composites on the basis of traditional photocatalysts were designed to solve above problems.The contents are as follows:（1）Synthesis of micro-nano hierarchical ZnO nanoflowers and their photocatalytic applications:Three kinds of micro-nano hierarchical ZnO nanoflowers with similar morphology and different superficial microstructure were prepared via a ultrasound-assisted hydrothermal technology and applied to photocatalytic pollutant degradation.We constructed ZnO materials after different ultrasonic intermediate processes.The three-dimensional（3D）ZnO nanoflowers were all composed by stacked nanosheets and showed a rule of ZnO-0>ZnO-250>ZnO-950 for photodegradation of methyl orange（MO）under ultraviolet light or simulated sunlight irradiation.There was no obvious transformation on integral morphology of ZnO materials.The different photocatalytic efficiency of ZnO nanoflowers mainly determined by their intrinsic features containing light absorption performance,specific surface area,intrinsic donor defects,reactive free radicals and so on.This work provides a good theoretical basis for intrinsic researches between ultrasonic treatment and 3D photocatalysts.（2）Synthesis of ZnO/N,S-CQDs composite nanoflower and its photocatalytic applications:In order to improve the photocatalytic efficiency of single ZnO material,we designed a surface-functionalized N,S-doped CQD（N,S-CQD）and embedded it into the micro-nano hierarchical ZnO for construction of a novel 3D nanoflower heterojunction for photodegradation of pollutants.The results showed that ZnO/N,S-CQDs_0.54 degraded 92.9%and 85.8%of ciprofloxacin（CIP）after simulated sunlight irradiation of 20 min and natural sunlight irradiation of 50 min,respectively.In addition,the ZnO/N,S-CQDs was able to degrade a variety of pollutants containing dyes and antibiotics simultaneously in the actual water system and showed a good prospect in industry.（3）Synthesis of N,S-CQDs/Bi2MoO6@TiO₂ ternary film and its photocatalytic applications:In order to improve the recycling ability of photocatalysts,we employed N,S-CQDs into the synthesis of a novel sponge-like N,S-CQDs/Bi2MoO6@TiO₂ ternary film on the TiO₂ arrays via a one-pot hydrothermal method.The film was applied to photodegradation and antibacterial researches.The results showed that the ternary film degraded 85.8%and 44.6%of CIP after 240 min irradiation of visible and NIR light,respectively,which were all obviously higher than that of binary Bi₂MoO₆@TiO₂and N,S-CQDs/TiO₂films.Moreover,the novel film possessed a better efficiency for photocatalytic sterilization than that of single and binary film,which was promising for more photoelectricity applications.（4）Synthesis of hollow core-shell TiO₂@g-C3N4 and its application of photocatalytic NADH regeneration:Inspired by the bionic concept,we constructed a kind of hollow core-shell TiO₂@g-C3N4 material with imitated thylakoid structure for photocatalytic NADH regeneration.It was found that the optimal regeneration efficiency reached to 96.6%after 60 min irradiation of simulated sunlight and 56.2%after 240 min irradiation of visible light at presence of[Cp*Rh（bpy）（H₂O）]²⁺mediator by the TiO₂@g-C3N4 material.Moreover,the regeneration ratio still remained 61.5%after 4 cycles,which presented certain structure stability and good applied efficiency of the material.Herein,a series of micro-nano hierarchical photocatalytic composites were synthesized on the basis of traditional photocatalysts.Three kinds of micro-nano hierarchical ZnO nanoflowers with similar configurations and different surface microstructures were synthesized via a ultrasound-assisted hydrothermal technology.Moreover,a new type of surface-functionalized N,S-doped CQD（N,S-CQD）was designed and embedded into the as-prepared ZnO nanoflower via a one-pot hydrothermal method for construction of 3D ZnO/N,S-CQDs heterojunction.The N,S-CQDs were further employed to regulate growth of a new spongy-like N,S-CQDs/Bi₂MoO₆@TiO₂ ternary composite film.These photocatalytic materials were applied to photodegradation and antibacterial researches.Finally,inspired by the bionic concept,a kind of hollow core-shell TiO₂@g-C₃N₄ material with imitated thylakoid structure was constructed for photocatalytic NADH regeneration.In this paper,various micro-nano hierarchical photocatalysts were constructed via different methods,which showed important values for different photocatalytic systems.