1：Experimental Design and Method Selection:

The study involved the synthesis of pure TiO2 and Al-Fe-Cu tri-doped TiO2 using in-situ hydrothermal method. The materials were characterized using XRD, FTIR, and SEM. Photocatalytic activity was evaluated under UV-visible light.

2：Sample Selection and Data Sources:

Samples included pure TiO2 and Al-Fe-Cu tri-doped TiO2 with varying amounts of Al dopant. Methylene blue dye was used for photocatalytic degradation tests.

3：List of Experimental Equipment and Materials:

Equipment included an autoclave, XRD (Rigaku Miniflex), FTIR (Perkin Elmer Spectrum 100), SEM (JSM 6360 Joey), and UV-vis spectrophotometer (Shimadzu UV-1800). Materials included titanium dioxide powder, aluminium (III) nitrate nanohydrate, iron (III) nitrate nanohydrate, and copper (II) nitrate trihydrate.

4：0). Materials included titanium dioxide powder, aluminium (III) nitrate nanohydrate, iron (III) nitrate nanohydrate, and copper (II) nitrate trihydrate. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: The synthesis involved hydrothermal treatment at 150°C for 24 hours, followed by washing, drying, and calcination at 500°C. Photocatalytic degradation was tested under UV lamp irradiation with methylene blue solution.

5：Data Analysis Methods:

XRD patterns were analyzed for crystallite size using Scherrer’s equation. FTIR spectra were analyzed for functional groups. Photocatalytic degradation rates were calculated based on absorbance measurements.