Exfoliation and Restacking Route to Anatase-Layered Titanate Nanohybrid with Enhanced Photocatalytic Activity

Abstract

A new microporous TiO2-pillared layered titanate has been prepared by hybridizing the exfoliated titanate with the anatase TiO2 nanosol. The stable colloidal nano-sheet was obtained by intercalating tetrabutylamine into the layered protonic titanate, HxTi2-x/4□x/4O4·H2O (x = 0.67), with a lepidocrocite-like structure. The colloidal suspension of exfoliated titanate sheets was mixed with the monodispersed anatase TiO2 nanosol solution prepared by the hydrolysis of titanium isopropoxide with acetylacetone. The obtained nanohybrid was heated at 300 °C for 2 h in order to complete the grafting reaction of intercalated anatase TiO2 nanosol on the interlayer surface of layered titanate. According to the X-ray diffraction analysis and N2 adsorption−desorption isotherms, it was found that the TiO2-pillared layered titanate showed a pillar height of ∼2 nm, a high surface area of ∼460 m2/g, and a pore size of ∼0.95 nm, indicating the formation of a microporous pillar structure. Its photocatalytic activity was evaluated by measuring the total volume of H2 gas evolved during the irradiation of the catalyst suspensions in water. The H2 gas evolution was found to increase from the layered titanate (cesium and protonic form) to the unsupported TiO2 (acac-TiO2) and the TiO2-pillared layered titanate, because the electron and hole recombination in the pillared system is thought to be effectively suppressed because of electron transfer between guest and host. A marked enhancement in the activity by ca. 40 times was obtained for TiO2-pillared layered titanate compared to pristine compounds such as layered titanate and anatase TiO2 nanosol when Pt (0.3 wt %) was doped on the surface of the sample.