1：Experimental Design and Method Selection:

The study used electrochemical anodization to prepare TiO2 nanotube arrays (TNA) and N-doped TNA (N-TNA) via ammonia annealing. Photocatalytic degradation of Acid Orange II (AO-II) under visible light was evaluated with and without H2O2 assistance.

2：Sample Selection and Data Sources:

A Ti foil (99% purity, 0.1 mm thickness) was used as the anode. AO-II dye (10 mg/L concentration) served as the organic pollutant model.

3：1 mm thickness) was used as the anode. AO-II dye (10 mg/L concentration) served as the organic pollutant model. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment included an electrochemical anodization setup with Ir/Ta alloy cathode, tubular furnace for annealing, X-ray diffractometer (D/max-IIIA), scanning electron microscope (SEM, LEO 1530VP), UV-Vis spectrometer (U3010, Hitachi), X-ray photoelectron spectrometer (XPS), photochemical reactor (XPA-II), 1000 W Xe lamp with filter, and spectrophotometer. Materials included HF, NH4F, 1,2,3-propanetriol, H2O2, ammonia gas (99.8%), and oxygen gas.

4：8%), and oxygen gas. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: Ti foil was cleaned with HF, anodized at 25 V for 2 h in electrolyte (1,2,3-propanetriol, NH4F, H2O), rinsed, dried, and annealed at 500°C in air or ammonia flow. Samples were characterized using XRD, SEM, XPS, and UV-Vis. Photocatalytic tests involved immersing samples in AO-II solution with H2O2, irradiating with visible light (λ > 400 nm) at 40°C and 180 mW/cm2, sparging oxygen, and measuring dye concentration over time.

5：Data Analysis Methods:

Data from characterization techniques were analyzed to assess microstructure, morphology, and optical properties. Photocatalytic efficiency was calculated based on the degradation percentage of AO-II, with comparisons made between different sample conditions.