1：Experimental Design and Method Selection:

The study involved synthesizing Ti3C2 MXene nanoparticles via a facile solvent exfoliation method and constructing TiO2/Ti3C2 heterostructures using a drop casting method to serve as photoanodes for PEC water splitting. Theoretical models and characterizations such as XRD, SEM, TEM, XPS, Raman, ESR, UV-Vis, EIS, and Mott-Schottky measurements were employed to analyze the materials and their performance.

2：Sample Selection and Data Sources:

Commercial Ti3AlC2 powders were used as the starting material for Ti3C2 synthesis. TiO2 nanorod arrays were synthesized on FTO glass substrates via a hydrothermal method. Data were collected from these synthesized samples and control experiments.

3：List of Experimental Equipment and Materials:

Equipment included an ultrasonic cell crusher (Biosafer, 650-92), XRD (Rigaku RINT 2100), SEM (JSM-7600F), TEM (JEOL-2010), XPS (ESCA-Lab220I-XL), UV-Vis-NIR spectrophotometer (Cary 5000), Raman spectrograph (HORIBA LabRAM HR), ESR spectrometer (Bruker E500), and electrochemical workstation (Gamry Interface 1000). Materials included Ti3AlC2 powders, HF, tetrabutyltitanate, FTO glass, Na2SO4 electrolyte, Pt plate counter electrode, and Ag/AgCl reference electrode.

4：0). Materials included Ti3AlC2 powders, HF, tetrabutyltitanate, FTO glass, Na2SO4 electrolyte, Pt plate counter electrode, and Ag/AgCl reference electrode. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: Ti3C2 was synthesized by etching Ti3AlC2 with HF, followed by ultrasonic exfoliation. TiO2 nanorods were grown on FTO via hydrothermal synthesis. Ti3C2 was deposited on TiO2 by drop casting. PEC measurements were conducted in a three-electrode setup with a Xe lamp light source, using linear-sweep voltammetry, EIS, and Mott-Schottky analysis.

5：Data Analysis Methods:

Data were analyzed using standard techniques for each characterization method, including peak deconvolution in XPS, bandgap calculation via Kubelka-Munk function, and impedance fitting in EIS. Statistical analysis was not explicitly mentioned, but comparative studies were performed.