Atomic layer deposited (ALD) TiO₂ on fibrous nano-silica (KCC-1) for photocatalysis: Nanoparticle formation and size quantization effect

Abstract

In this work we report the design and synthesis of high-surface-area photocatalysts by coating TiO₂ on fibrous nanosilica (KCC-1) using atomic layer deposition (ALD). Our developed catalyst showed enhanced photocatalytic activity, better than that of the well-known MCM-41- and SBA-15-supported TiO₂ catalysts using ALD as well as that of other silica-supported TiO₂ catalysts reported in the literature to date. This work shows how one can tune the photocatalytic activity of supported TiO₂ catalysts by simply tuning the morphology of the support. In addition to extensive characterization of materials using various techniques, comprehensive mechanistic insight into ALD TiO₂ coating on KCC-1 fibers was gained using solid-state NMR and UV-DRS. For the first time, we also observed the formation of small and monodispersed TiO₂ nanoparticles after heat treatment of these ALD-coated samples of KCC-1. Notably, we observed size quantization effects in these TiO₂ nanoparticles, which was confirmed by band gap shift measurements and the Brus effective mass approximation method. We believe that the combination of the unique textural properties and morphology of KCC-1 and TiO₂ nanoparticle formation and their size quantization is the reason behind the enhanced photocatalytic activity of KCC-1/TiO₂ catalysts.