Controlled Regulation of N-Involved TiO2 Nanoflowers in Size and Morphology via Solvothermal Synthesis for Enhanced Photocatalytic Performance

The precise control of size and morphology of photocatalysts through solvothermal methods is a challenge in the basic research of 3-D titanium dioxide (TiO₂) hierarchical structures. This study utilizes the solvothermal method to synthesize N-involved TiO₂ nanoflowers with nanosheet-assembled structures ranging from microscale (1.3 µm ± 0.2 µm) to nanoscale (200 nm ± 50 nm), achieved by varying the volume fraction (percentage by volume, vol%) of N-N-dimethylformamide (DMF) from 0% to 75% in a mixed solution of DMF and isopropanol (IPA). The synthesized TiO₂:VF_DMF = 0–75% catalyst exhibits good monodispersity and uniform particle size. With increasing DMF volume percentage, the size of TiO₂:VF_DMF = 0–75% decreased regularly, and the number of nanosheets constructed with a single TiO₂:VF_DMF = 0–75% particle decreased without any stacking or reassembly occurring. This study monitors the solvothermal processes of DMF 5% and DMF 75%, revealing the changing rules of nanoparticle size and morphology. Furthermore, the photocatalytic degradation of methyl orange shows that TiO₂:VF_DMF = 50% and TiO₂:VF_DMF = 75% are structurally stable and exhibit good photocatalytic activity without any noble metal doping. The degradation efficiency reaches 99.9%, and after repeated use, the catalysts demonstrate excellent degradation performance.