Preparation of morphology-controlled TiO₂ nanocrystals for the excellent photocatalytic activity under simulated solar irradiation

Graphical abstract: Morphology-controlled TiO₂ nanocrystals with excellent photocatalytic activity under simulated solar irradiation were successfully synthesized. - Highlights: • TiO₂ nanocrystals (NCs) with different morphologies were synthesized. • The growth mechanism of morphology-controlled TiO₂ NCs was proposed. • The core-shell structured TiO₂ NCs (co-TiO₂) had a narrow band gap (2.67 eV). • The co-TiO₂ NCs possessed excellent photocatalytic activity and recyclability. - Abstract: A simple synthetic approach based on solvothermal technique and hydrogenation was developed for preparation of TiO₂ nanocrystals with different morphologies such as elongated rhombic, dog-bone, oval and core-shell structured oval. The effect of oleic acid (OA) and oleylamine (OM) as two capping surfactants on the growth of TiO₂ nanocrystals was investigated. The physicochemical properties of the obtained samples were characterized by various techniques including TEM, XRD, UV–vis absorption, Raman, XPS, BET, PL and photocurrent measurement. In photodegradation of RhB under simulated solar irradiation, the oval-shaped TiO₂ nanocrystals with core-shell structure (co-TiO₂) was superior to other TiO₂ nanocrystals in catalytic activity. Moreover, the co-TiO₂ nanocrystals exhibited well recyclability during multiple photocatalytic tests. These excellent properties of co-TiO₂ were attributed to its special structure, including lattice-disordered surface layer and well-crystallized lattice core, and narrow band gap (2.67 eV).