1：Experimental Design and Method Selection:

The study involved synthesizing g-C3N4/SrTiO3 nanocomposites via a two-step mechanically milling and calcination process to explore interfacial interactions and photocatalytic performance. Theoretical models included DFT calculations for electronic structure analysis.

2：Sample Selection and Data Sources:

Samples included pure g-C3N4, SrTiO3, and nanocomposites with 3%, 5%, and 10% SrTiO3 content, prepared using analytical grade chemicals like urea and SrCO

3：List of Experimental Equipment and Materials:

Equipment included a muffle furnace for calcination, high energy mill machine for milling, XRD (Philips X'Pert Pro), SEM (Hitachi S-4800), TEM (JEM-2100), XPS (PHI 5000 VersaProbe), BET surface area analyzer (Micrometrics ASAP-2020), FT-IR spectrometer (Nicolet 5700), UV-vis DRS (Shimadzu UV-2401), PL spectrophotometer (Fluoromax-4), electrochemical workstation (CHI660A), and photocatalytic reactor (Ceaulight CEL-SPH2N-D). Materials included urea, SrCO3, rutile, NaCl, KCl, triethanolamine, H2PtCl6, and Nafion.

4：Experimental Procedures and Operational Workflow:

Synthesis involved calcining urea to make g-C3N4, mixing with SrTiO3 via ball milling, and calcining. Characterization included structural, morphological, and optical analyses. Photocatalytic tests measured H2 evolution under visible light with a Xe lamp and cut-off filter, using triethanolamine as a sacrificial agent and Pt as a co-catalyst.

5：Data Analysis Methods:

Data were analyzed using XRD for crystal structure, SEM/TEM for morphology, XPS for electronic structure, BET for surface area, UV-vis DRS for optical properties, PL for charge recombination, photoelectrochemical measurements for charge separation, and DFT calculations for charge density differences.