1：Experimental Design and Method Selection:

The study involves synthesizing TiO2 nanorod arrays, growing g-C3N4 on them, and applying phosphide gas treatment for doping and cocatalyst formation. Methods include thermal polymerization, annealing, and photoelectrochemical measurements.

2：Sample Selection and Data Sources:

Samples include TiO2 nanorods, g-C3N4 films, and doped variants. Data from characterization techniques like SEM, TEM, XRD, XPS, UV-Vis, PL, and electrochemical tests.

3：List of Experimental Equipment and Materials:

Equipment includes field-emission SEM (Zeiss ULTRA Plus), XRD (PANalytical X'Pert PRO), TEM (JEM-1200EX FEI), UV-Vis spectrometer (Shimadzu UV-2550), XPS (Kratos Axis Ultra DLD), PL spectrophotometer (FLS920), electrochemical workstation (CHI-660D), and LED light sources. Materials include titanium butoxide, HCl, cyanuric acid, 2,4-diamino-6-phenyl-1,3,5-triazine, copper nitrate, ferric nitrate, ethanol, sodium hypophosphite, and FTO glass.

4：Experimental Procedures and Operational Workflow:

Synthesis of TiO2 nanorods via hydrothermal method, preparation of g-C3N4 films by thermal polymerization, phosphide annealing for doping, immersion in metal nitrate solutions followed by phosphide annealing for cocatalyst formation, and characterization and photoelectrochemical testing in 1.0 M NaOH electrolyte.

5：0 M NaOH electrolyte. Data Analysis Methods:

5. Data Analysis Methods: Data analyzed using techniques like Kubelka-Munk function for band gap estimation, equivalent circuit fitting for EIS, and IMPS for kinetic parameters.