1：Experimental Design and Method Selection:

The study used hydrothermal and aqueous chemistry methods to synthesize hierarchical TiO2 nanostructures. The design aimed to optimize parameters for crack-free, uniform films with specific morphological and phase properties.

2：Sample Selection and Data Sources:

Fluorine doped tin oxide (FTO) glass was used as the substrate. Materials included titanium butoxide, titanium tetrachloride, sodium chloride, hydrochloric acid, 2-propanol, acetone, ammonium hexa?uorotitanate, and boric acid, all analytical-grade.

3：List of Experimental Equipment and Materials:

Equipment included a scanning probe microscope (SPM; VEECO), field emission scanning electron microscope (FESEM; MIRA3TESCAN-XMU), energy dispersive spectroscopy (EDS; JEOL JED-2300), X-ray diffractometer (XRD; X′Pert PRO MPD, PANalytical), Raman spectrometer (Horiba Jobin Yvon modular Raman spectrometer with Stellar Pro Argon-ion laser), and UV–vis spectrophotometer (Avaspec-2048-TEC with AvaLamp DH-S Setup). Materials were as listed in section 2.

4：Experimental Procedures and Operational Workflow:

1. 4. Experimental Procedures and Operational Workflow: Synthesis involved preparing a TiO2 seed layer on FTO using TiCl4 hydrolysis and calcination, growing TiO2 nanorod array via hydrothermal method at 150°C for 15h, and synthesizing nano?owers via aqueous chemistry with boric acid and ammonium hexa?uorotitanate at room temperature for 40h. Characterizations included SPM, FESEM, EDS, XRD, Raman spectroscopy, and diffuse transmittance spectroscopy.

5：0h. Characterizations included SPM, FESEM, EDS, XRD, Raman spectroscopy, and diffuse transmittance spectroscopy. Data Analysis Methods:

5. Data Analysis Methods: Data were analyzed using techniques such as XRD for crystal structure, Raman for phase identification, and UV–vis for band gap estimation using absorption coefficient calculations.