Chimie douce route to sodium hydroxo titanate nanowires with modulated structure and conversion to highly photoactive titanium dioxides

Chih Wei Peng, Mireille Richard-Plouet, Tsung Yin Ke, Chi Young Lee*, Hsin-Tien Chiu, Christiane Marhic, Eric Puzenat, Frederic Lemoigno, Luc Brohan

*Corresponding author for this work

Research output: Contribution to journalArticle

44 Scopus citations

Abstract

Sodium hydroxo titanate nanowires with NaTi2O4(OH) formulation are fabricated by chimie-douce from TiO2 powders in a hot concentrated base solution. In the present work, we investigate, in detail, the structure and morphology of the titanate, acid-exchanged materials, and phases formed during dehydration of these compounds; we then discuss the relationship between the initial titanate structure and TiO2 formation. XRD, ED, HRTEM, EDS, density measurements, and TG/MS results suggest that the titanate and acid-exchanged structures were closely related to the pseudolepidocrocite arrangement ("Cs2Ti6O12" type). The average structure of NaTi2O4(OH) nanowires consists of noncorrugated Ti2O3(OH) and NaO layers stacked along the [010] direction and an energy minimization was further conducted by theoretical methods. From TEM study, we demonstrated that NaTi2O4(OH) exhibits a modulated structure (q wave vector equals to 1/7 [001]*), which originates from the misfit between the NaO and Ti2O3(OH) sublattices. NaTi2O4(OH) structure has a monoclinic distortion (I2/m space group) with refined unit cell a = 0.37000(6) nm, b = 1.7816(4) nm, c = 2.2077(3) nm, β= 92.70(1)°. Proton exchange followed by heat treatment convert the sodium hydroxo titanate into highly photoactive TiO2 nanowires. The activity is attributed to the presence of preferentially exposed (001) surface plane which is explained by the topotactic phase transformation of TiO2(B) into anatase.

Original languageEnglish
Pages (from-to)7228-7236
Number of pages9
JournalChemistry of Materials
Volume20
Issue number23
DOIs
StatePublished - 9 Dec 2008

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