1：Experimental Design and Method Selection:

The study involved synthesizing Sr2Ta2O7 nanosheets via a hydrothermal method and then hybridizing them with S-doped g-C3N4 through thermal condensation. Pt cocatalyst was loaded using an impregnation method. The design aimed to enhance charge separation and transfer for improved photocatalytic activity.

2：Sample Selection and Data Sources:

Samples included pure Sr2Ta2O7, S-doped g-C3N4 (CNS), and nanocomposites with different mass ratios (STO/CNS-1, STO/CNS-2, STO/CNS-3). Data were obtained from laboratory experiments.

3：3). Data were obtained from laboratory experiments. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Chemicals such as Ta2O5, Sr(NO3)2, thiourea, H2PtCl6·6H2O, NaOH, CH3OH from Aladdin and Sinopharm Chemical Reagent Co., Ltd. Equipment included XRD (Rigaku D/max 2550), SEM (Nova Nano 230), TEM (JEM-2100F), XPS (ESCALAB 250Xi), UV–vis spectrometer (Evolution 220), FT-IR spectrometer (Bruker Tensor 27), PL spectrophotometer (F-4600), fluorescence spectrometer (FLS980), electrochemical workstation (CHI660), and a photocatalytic reaction system with a Xe lamp and gas chromatography.

4：Experimental Procedures and Operational Workflow:

Sr2Ta2O7 was synthesized hydrothermally at 533 K for 72 h. Nanocomposites were prepared by grinding and annealing mixtures of Sr2Ta2O7 and thiourea at 673 K. Pt loading was done via impregnation and reduction at 623 K. Characterizations involved XRD, TEM, XPS, DRS, FT-IR, PL, and photoelectrochemical tests. Photocatalytic reactions were conducted in a closed system with visible light irradiation, and hydrogen evolution was measured.

5：Data Analysis Methods:

Data were analyzed using techniques such as Kubelka-Munk transformation for band gap calculation, fitting of XPS spectra, and interpretation of PL, EIS, and photocurrent responses to assess charge separation and transfer.