Atomic Layer Deposited (ALD) TiO2 on Fibrous Nano-Silica (KCC-1) for Photocatalysis: Nanoparticle Formation and Size Quantization Effect

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.