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

Abstract

A new microporous TiO 2 -pillared layered titanate has been prepared by hybridizing the exfoliated titanate with the anatase TiO 2 nanosol. The stable colloidal nano-sheet was obtained by intercalating tetrabutylamine into the layered protonic titanate, H x Ti 2-x/4 0 x/4 O 4 ‚H 2 O (x ) 0.67), with a lepidocrocite-like structure. The colloidal suspension of exfoliated titanate sheets was mixed with the monodispersed anatase TiO 2 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 TiO 2 nanosol on the interlayer surface of layered titanate. According to the X-ray diffraction analysis and N 2 adsorption-desorption isotherms, it was found that the TiO 2 -pillared layered titanate showed a pillar height of ∼2 nm, a high surface area of ∼460 m 2 /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 H 2 gas evolved during the irradiation of the catalyst suspensions in water. The H 2 gas evolution was found to increase from the layered titanate (cesium and protonic form) to the unsupported TiO 2 (acac-TiO 2 ) and the TiO 2 -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 TiO 2pillared layered titanate compared to pristine compounds such as layered titanate and anatase TiO 2 nanosol when Pt (0.3 wt %) was doped on the surface of the sample.

Porous Titania Nanosheet/Nanoparticle Hybrids as Photoanodes for Dye-Sensitized Solar Cells

“…In addition, we hypothesize the electron-hole recombination would be effectively suppressed due to the charge transfer between the guest and host in the layered NH system. 22,23,31 An enhanced overall conversion efficiency of 10.1% for layered titania nanosheet/ nanoparticle hybrid photoanode was achieved, a noticeable 29.5% improvement compared with the photoelectrode made of the benchmark Degussa TiO2 P25 under the same testing conditions. Various characterizations confirmed our hypothesis and the feasibility of using new layered NH photoanodes for efficiency improvement of DSSCs.…”

“…Table 1 22,23,30,31,53,54 within the layered NH film, which results in an increase in electron density in TiO2, and thus the shift of Fermi level. 55 As evidenced above, the large surface area makes it accessible for more dye-adsorption, and the light scattering effect of the re-assembled exfoliated titanates favour enhanced light-harvesting efficiency by increasing the optical length serving as light-scattering shield, and thereby enhanced Jsc for the cell with the layered NH film.…”

“…Layered nanohybrids (NHs) by pillaring semiconducting nanoparticles such as CdS, α-Fe2O3, and TiO2 [21][22][23][24] into layered inorganic compounds [25][26][27][28][29][30] have recently drawn growing attention in photocatalysis, due to their large surface area as well as suppressed electronhole recombination because of electron transfer between guest and host. 22,23,31 Titanate nanosheets (Ti0.91O2) derived from delamination of layered compounds have unique structural characteristic of ultimate two-dimensional anisotropy with extremely small thickness in the subnano-to nanometer scales, which leads to new physical and chemical properties for nanosheets.…”

“…22,23,31 Titanate nanosheets (Ti0.91O2) derived from delamination of layered compounds have unique structural characteristic of ultimate two-dimensional anisotropy with extremely small thickness in the subnano-to nanometer scales, which leads to new physical and chemical properties for nanosheets. 32 In addition, the exfoliation of layered metal oxides into 2D nanosheets 33,34 (Ti0.91O2 nanosheets) makes it possible to pillar large-sized (TiO2) nanoparticles into the interlayer space of host materials through an exfoliation-restacking process of nanosheets and guest particles.…”

“…32 In addition, the exfoliation of layered metal oxides into 2D nanosheets 33,34 (Ti0.91O2 nanosheets) makes it possible to pillar large-sized (TiO2) nanoparticles into the interlayer space of host materials through an exfoliation-restacking process of nanosheets and guest particles. 23,35,36 The obtained pillared NHs possesses highly controllable physical and chemical properties. 22,[37][38][39] In particular, due to the enlarged interlayer distance, the total surface area is significantly increased, facilitating chemical adsorption or reaction.…”