Photocatalysis by morphologically tailored mesoporous silica (SBA-15) embedded with SnO2 nanoparticles: Experiments and model

Abstract

Commonly obtained SBA-15 particles (fiber-like morphology), if used as a catalyst-host, has limitations in diffusion of reactant molecules (e.g. of a dye) inside the pores of the SBA-15 particle. The systematic synthetic approach developed here provides an easy control of SBA-15 particle morphology over a wide range (fiber, rod, and sphere), by only varying the HCl concentration. To assess its effect on molecular diffusion and reaction inside pores, SnO2 nanoparticles of 3.5nm diameter were synthesized in situ, inside the 6.3nm diameter pores of SBA-15. These hybrids were tested for photocatalytic degradation of rhodamine B dye. Sphere-like morphology of SBA-15 with SnO2 nanoparticle loading of 17.7wt% showed the highest first-order degradation rate constant of 0.54h−1, compared to other morphologies (rod—0.51h−1, fiber—0.33h−1). On incorporating rates of diffusion, adsorption, and degradation-reaction of the dye in a single pore-level mathematical model of the SBA-15 particle, we have predicted the experimentally measured temporal variation of dye concentration for different SBA-15 morphologies and SnO2-catalyst loadings. Therefore, the present work identifies the best SBA-15 particle morphology (sphere-like) for such reactions and provides a validated model to optimize such coupled problems of chemical transport and reaction.