Fabrication And Photocatalytic Performance Of Supported TiO₂Nanoparticles Derived From Layered Double Hydroxide Precursors

The TiO₂-based materials with the advantages of stable performance,non-toxic, low cost and high activity are always the hotspot of photocatalyticresearch. And the development of new approach for preparation of supportedTiO₂-based photocatalysts with improved activity and stability is thus highlyvalued. Layered double hydroxides （LDHs） with flexibility in compositionand the attractive “reconstruction effect” features offers the possibility toachieve this vision. Herein, supported TiO₂nanoparticles have beensuccessfully fabricated by selective reconstruction of a Cu²⁺, Mg²⁺, Al³⁺,Ti4+-containing layered double hydroxide （CuMgAlTi–LDH） precursor,synthesized by coprecipitation, through calcination and rehydration process.A systematic investigation of the structural characterization and thephotodegradation tests of methylene blue （MB） dye molecules from solutionunder both UV and visible light irradiation for the resultingTiO₂/CuMgAl-RLDH sample were carried out. In order to have a betterunderstand of the reaction mechanism, the test on decomposition of formaldehyde was provided. Anatase-type TiO₂nanoparticles are found to behomogeneously distributed on the surface of the selectively-reconstructedCuMgAl-RLDH support. And the direct evidence for the surface TiO₂/LDHheterojunction formed on CuMgAl-RLDH is presented. For MBphotodegradation under UV light or visible light illumination,TiO₂/CuMgAl-RLDH sample has superior photocatalytic properties to therehydrated single phase R-TiO₂, the physical mixture of R-TiO₂andCuMgAl-RLDH, the composite CuTi/MgAl-RLDH synthesized by therehydration of mixture of MgAl-MMO and CuTi-MMO, and theTiO₂/MgAl-RLDH prepared under the same procedure asTiO₂/CuMgAl-RLDH without containing Cu ions. For formaldehydephotodegradation, confirmed the existence of dye-sensitized photocatalyticdegradation for TiO₂/CuMgAl-RLDH under visible light irradiation. Butunder UV light irradiation, TiO₂/CuMgAl-RLDH also shows the bestphotocatalytic activity. The skeleton Cu2+ions dispersed in the mainlayer ofCuMgAl-RLDH support can enable the photocatalytic activity. The TiO₂/LDHheterojunction nanostructure is proposed to contribute the efficient spatialseparation between the photogenerated electrons and holes, which canconcomitantly improve the photocatalytic activity.