Highly Dispersed TiO6 Units in a Layered Double Hydroxide for Water Splitting

A family of photocatalysts for water splitting into hydrogen was prepared by distributing TiO₆ units in an MTi‐layered double hydroxide matrix (M=Ni, Zn, Mg) that displays largely enhanced photocatalytic activity with an H₂‐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 TiO₆ octahedra in the layered doubled hydroxide (LDH) matrix was obtained by the formation of an M²⁺‐O‐Ti network, rather different from the aggregation state of TiO₆ in the inorganic layered material K₂Ti₄O₉. 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 TiO₆ units was modified by the adjacent MO₆ 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 TiO₆ 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.