Enhanced photocatalytic properties of hierarchical three-dimensional TiO2 grown on femtosecond laser structured titanium substrate

Three-dimensional micro-/nanostructured TiO2 (3D-TiO2) fabricated on titanium substrate effectively improves its performance in photocatalysis, dye-sensitized solar cell and lithium-ion battery applications. In this study, the hierarchical 3D-TiO2 with anatase phase directly grown on femtosecond laser structured titanium substrate is reported. First, the primary columnar arrays were fabricated on the surface of titanium substrate by femtosecond laser structuring. Next, the secondary nano-sheet substructures were grown on the primary columnar arrays by NaOH hydrothermal treatment. Followed by ion-exchange process in HCl and annealing in the air, the hierarchical anatase 3D-TiO2 was achieved. The hierarchical anatase 3D-TiO2 exhibited enhanced performances in light harvesting and absorption ability compared to that of nano-sheet TiO2 grown on flat titanium surface without femtosecond laser structuring. The photocatalytic degradation of methyl orange reveals that photocatalytic efficiency of the hierarchical anatase 3D-TiO2 was improved by a maximum of 57% compared to that of nano-sheet TiO2 (55% vs 35%). Meanwhile, the hierarchical anatase 3D-TiO2 remained mechanically stable and constant in consecutive degradation cycles, which promises significance in practical application.