New insights into the photocatalytic activity of 3-D core–shell P25@silica nanocomposites: impact of mesoporous coating

Abstract

In this report, a three-dimensional (3-D) network of core–shell TiO₂ (P25)–mesoporous SiO₂ (P25@mSiO₂) nanocomposites was prepared via a controllable surfactant-assisted sol–gel method. The nanocomposites were investigated for photocatalytic reactions of organic dye degradation, water splitting, and CO₂ reduction to understand the roles of the mSiO₂ shell in these photocatalytic reactions. It was found that the mSiO₂ shell accelerates the photodegradation of the organic dye, but dramatically reduces the photocatalytic activity of P25 in water splitting and CO₂ reduction. The roles played by the mSiO₂ shell in the photocatalytic reactions are summarized as: (1) effective prevention of agglomeration of P25 nanoparticles, (2) facilitating the transfer of uncharged photo-generated ˙OH radicals via the abundant –OH groups on the mesoporous surface, (3) provision of increased reaction sites between ˙OH radicals and dye molecules by its mesoporous nanostructure and large surface area, and (4) prevention of diffusion of the photo-generated charge carriers (photoelectrons and photoholes) because of its insulating nature.