Synthesis of novel TiO2/BiOCl@HHSS composites and its photocatalytic activity enhancement under simulated sunlight

Abstract

A novel TiO₂/BiOCl@HHSS photocatalyst (TiO₂/BiOCl heterostructured semiconductor supported on hierarchical hollow silica spheres (HHSS)) was synthesized by a facile one-pot method, and further characterized by XRD, HRTEM, SEM, N₂ adsorption–desorption analysis and UV-vis diffuse reflectance spectra. Structural characterization indicated that the as-synthesized TiO₂/BiOCl@HHSS photocatalyst possessed a special small-hollow-sphere@big-hollow-sphere structure with a diameter of 90–150 nm and a high specific surface area of 414.3 m² g⁻¹. The TiO₂/BiOCl nanoparticles with smaller crystallite size were well dispersed on the HHSS, due to its unique hierarchical sphere structure which composed of much smaller hollow spheres (∼20 nm) covered by external wall. The photocatalytic activity of the photocatalyst was investigated by the degradation of reactive brilliant red (RBR) under simulated sunlight. The TiO₂/BiOCl@HHSS composite shows the highest photocatalytic activity among TiO₂/BiOCl, TiO₂@HHSS and BiOCl@HHSS catalysts, due to its special hollow structure, high surface area and heterostructure. A possible mechanism is proposed to explain the degradation of organic dye molecules over the BiOCl/TiO₂@HHSS nanocomposite photocatalyst. The proposed grafting strategy on porous support for the formation of this hybrid photocatalyst can also be applied to other semiconductor candidates resulting in improved photocatalytic performance.