Controlled synthesis of TiO2 nanorod arrays immobilized on ceramic membranes with enhanced photocatalytic performance

In this work, TiO2 nanorod arrays (NRAs) were synthesized directly on flat sheet Al2O3 ceramic membrane (CM) substrates by a two-step hydrothermal method. The effects of the addition of anions and cations and the preparation parameters in the second step on the morphology and size of TiO2 were investigated in detail, and the photocatalytic activities of the as-synthesized TiO2-loaded ceramic membranes were investigated by the degradation of methylene blue (MB) under UV light. The results highlighted that the growth of TiO2 on the CM strongly depended on the synthesis conditions. The anions of Cl- and Br- were favorable for the further growth of TiO2 nanorods, while the anions of SO42- and PO43- with larger ionic radius and higher charge number could retard the growth of TiO2 nanorods. The SO42- and PO43- could accelerate the formation of nanospheres or nanosheets, respectively. The cation like Na+, K+, Mg2+ and Ca2+ had no obvious impact on the formation of TiO2 NRAs. TiO2 nanorods exhibited the highest photocatalytic activity, as about 2.2 and 1.9 times larger than those of TiO2 nanosheets and TiO2 nanospheres, respectively. More importantly, the as-synthesized TiO2 NRAs-loaded ceramic membrane could be easily reused and exhibited better photocatalytic stability. These findings would aid the development of TiO2 photocatalytic materials with high performance.