Comparison of SiO2/TiO2 photocatalysts with different thicknesses synthesized by fluidized bed atomic layer deposition

SiO2/TiO2 core/shell particles are effective photocatalysts, whose performance strongly depends on TiO2 film thicknesses. Fluidized bed atomic layer deposition (FBALD) can precisely control film thickness at the sub-nanometer scale. In this work, TiO2 films with different thicknesses are deposited on SiO2 particles via different ALD cycles at 180 °C in a fluidized bed reactor. TEM images indicate that complete and uniform nanoscale TiO2 films (0.7–6.4 nm, corresponding to 5–50 ALD cycles) are formed on SiO2 surface. The TiO2 film with about 3.9 nm is found to exhibit the highest photocatalytic characteristics by degrading rhodamine-B (RhB) and tetracycline (TC), and the photocatalytic activity is further maintained above 90% after 6 cycles of photocatalytic reaction. Suitable TiO2 film thickness shows minimal charge transfer resistance, resulting in enhanced photon adsorption and separation of electrons and holes, thus improving photocatalytic performance. This work provides an effective way to tune the photocatalytic performance via FBALD.