表面氟化TiO_(2)空心光催化剂制备及其应用

Fluorinated TiO_(2) Hollow Photocatalysts for Photocatalytic Applications

空心结构和特定表面功能赋予球形组装体卓越的高性能与新特性,在催化、光催化、能量转换、存储以及生物医学等领域具有广阔的应用前景。以作者团队的研究结果为主,本综述概述了表面氟化TiO_(2)多孔空心微球(F-TiO_(2) PHMs)的制备及其光催化应用进展。本文中,F-TiO_(2) PHMs的合成策略主要包括简化的两步模板法,以及基于氟诱导自转变机制(FMST)的无模板法。与两步模板法相比,FMST法中模板的形成、包覆与去除都在"黑箱"式的一步反应中完成,无需额外的认为处理步骤。FMST法制备F-TiO_(2) PHMs暗含四个基本步骤:成核、自组装、表面再结晶与自转变。通过控制FMST法的四个基本步骤,经过简单的水热处理可以成功制备高产量的F-TiO_(2) PHMs,同时F-TiO_(2) PHMs的多层次微观结构参数,如空腔、多级孔、一次纳米粒子的组成与结构等,均可以很好地裁剪调控。F-TiO_(2) PHMs在光催化应用中具有增强光吸收、促进传质、降低膜污染等结构优势。同时,F-TiO_(2) PHMs制备过程原位引入表面氟修饰,带来显著表面氟效应,不仅有利于反应物分子的吸附和活化,而且有利于光生电子和空穴的表面俘获和界面转移。并且,多孔空心结构对客体修饰,如离子掺杂、基团功能化和纳米粒子负载等,表现出更好的相容性和耐受性,可以进一步提高F-TiO_(2) PHMs的光催化性能。结合F-TiO_(2) PHMs的主客体协同修饰作用,可以同时增强光吸收范围与强度,降低电荷复合几率,促进传质与吸附,提高表面反应效率,因此整个光催化过程可以综合调控协同优化。综上所述,F-TiO_(2) PHMs具有丰富的组成/结构参数和优异的理化性质,结合空心结构、分等级多孔性、表面氟化等特征,以及主/客体协同修饰作用,实现一体化调控复杂的光催化过程,改善光催化性能,为光催化技术潜在应用发展提供保障。

Recently,extensive studies have been carried out to synthesize spherical microassemblies with hollow interiors and specific surface functionalizations,which usually exhibit fascinating enhanced or emerging properties and have promising applications in catalysis,photocatalysis,energy conversion and storage,biomedical applications,etc.With particular emphasis on the results obtained mainly by the authors’research group,this review provides a brief summary of the recent progress on the fabrication and potential photocatalytic applications of fluorinated TiO_(2) porous hollow microspheres(F-TiO_(2) PHMs).The synthesis strategies for F-TiO_(2) PHMs include a simplified two-step templating method and template-free method based on the fluoride-mediated self-transformation(FMST)mechanism.Compared to the two-step templating method,the template formation,coating,and removal steps for the FMST method are programmatically proceeded in"black-box"-like one-pot reactions without additional manual steps.The four underlying steps involved in the fabrication of F-TiO_(2) PHMs through the FMST pathway,nucleation,self-assembly,surface recrystallization,and self-transformation,are presented.By controlling these four steps in the FMST pathway,F-TiO_(2) PHMs can be successfully fabricated with a high yield by a simple one-pot hydrothermal treatment.The multi-level microstructural characteristics(including the interior cavity and hierarchical porosity)and compositions of hollow TiO_(2) microspheres as well as the primary building blocks can be well tailored.The unique superstructures of the F-TiO_(2) PHM photocatalysts provide advantages for photocatalytic applications by improving the light harvesting,mass transfer,and membrane antifouling.In addition,the in situ-introduced surface fluorine species during the formation of F-TiO_(2) PHMs provide significant surface fluorination effects,which are not only favorable for the adsorption and activation of reactant molecules,but also beneficial for surface trapping and interfacial transfer of photo-excited electrons and holes.Moreover,the porous hollow superstructures exhibit considerably better compatibility and tolerance to guest modifications,and thus the photocatalytic performances of F-TiO_(2) PHMs can be increased by synergetic host and guest modifications,such as ion doping,group functionalization,and nanoparticle loading.The light-harvesting range and intensity can be increased,the charge recombination can be reduced,mass transfer and adsorption can be promoted,and the surface reactivity can be tuned by introducing specific surface functionalities or nanoparticular cocatalysts.Consequently,the entire photocatalytic process can be systematically modulated to optimize the overall photocatalytic performance.The as-prepared F-TiO_(2) PHMs typically integrate the merits of interior cavity,hierarchical porosity,and surface fluorination and are open to synergetic host-guest modifications,which provides abundant compositional/structural parameters and specific physicochemical properties for systematically modulating the interconnected photocatalytic processes and promising potential photocatalytic applications.