title: Highly dispersed TiO6 units in a layered double hydroxide for water splitting.
abstract: A family of photocatalysts for water splitting into hydrogen was prepared by distributing TiO(6) units in an MTi-layered double hydroxide matrix (M = Ni, Zn, Mg) that displays largely enhanced photocatalytic activity with an H(2)-production rate of 31.4 μmol  h(-1) as well as excellent recyclable performance. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) mapping and XPS measurement reveal that a high dispersion of TiO(6) octahedra in the layered doubled hydroxide (LDH) matrix was obtained by the formation of an M(2+)-O-Ti network, rather different from the aggregation state of TiO(6) in the inorganic layered material K(2)Ti(4)O(9). Both transient absorption and photoluminescence spectra demonstrate that the electron-hole recombination process was significantly depressed in the Ti-containing LDH materials relative to bulk Ti oxide, which is attributed to the abundant surface defects that serve as trapping sites for photogenerated electrons verified by positron annihilation and extended X-ray absorption fine structure (EXAFS) techniques. In addition, a theoretical study on the basis of DFT calculations demonstrates that the electronic structure of the TiO(6) units was modified by the adjacent MO(6) octahedron by means of covalent interactions, with a much decreased bandgap of 2.1 eV, which accounts for its superior water-splitting behavior. Therefore, the dispersion strategy for TiO(6) units within a 2D inorganic matrix can be extended to fabricate other oxide or hydroxide catalysts with greatly enhanced performance in photocatalysis and energy conversion.
authors.affiliation: State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, 100029, Beijing, PR China.
authors.forename: Yufei
authors.initials: Y
authors.lastname: Zhao
authors.forename: Pengyun
authors.initials: P
authors.lastname: Chen
authors.forename: Bingsen
authors.initials: B
authors.lastname: Zhang
authors.forename: Dang Sheng
authors.initials: DS
authors.lastname: Su
authors.forename: Shitong
authors.initials: S
authors.lastname: Zhang
authors.forename: Lei
authors.initials: L
authors.lastname: Tian
authors.forename: Jun
authors.initials: J
authors.lastname: Lu
authors.forename: Zhuoxin
authors.initials: Z
authors.lastname: Li
authors.forename: Xingzhong
authors.initials: X
authors.lastname: Cao
authors.forename: Baoyi
authors.initials: B
authors.lastname: Wang
authors.forename: Min
authors.initials: M
authors.lastname: Wei
authors.forename: David G
authors.initials: DG
authors.lastname: Evans
authors.forename: Xue
authors.initials: X
authors.lastname: Duan