Organic free low temperature direct synthesis of hierarchical protonated layered titanates/anatase TiO2 hollow spheres and their task-specific applications

Abstract

Layered protonated titanates and corresponding anatase TiO₂ shapes, specifically the hollow spheres, are the most important functional materials and have attracted much attention because of their superior performance. Here, a facile organic substrate (both as solvent or surfactant) free, low temperature aqueous solution based chemical protocol for the direct synthesis of 3D arranged hierarchical hollow spheres of protonated layered dititanate (H₂Ti₂O₅·H₂O), is proposed. The spheres had a high surface area (as high as 334 m² g⁻¹), and were prepared through hydrothermal treatment of freshly prepared peroxo titanium carbonate complex in the presence of ammonium hydroxide. Ammonium hydroxide is crucial in the formation of spherical arrangement of titanate sheets and the size of the spheres is tunable by changing the amount of ammonium hydroxide. The titanate spheres can easily be converted to pure anatase TiO₂ with identical morphology on subsequent calcination. The synthesized titanate spheres showed very high removal capacity for toxic heavy metals like Pb²⁺ and methylene blue from aqueous solution. Corresponding anatase TiO₂ spheres manifested as a brilliant anode material for lithium ion batteries with excellent cyclability. TiO₂ spheres also showed good photocatalytic activity.