1：Experimental Design and Method Selection:

The study involved synthesizing La2Ti2O7 nanosheets via hydrothermal method and In2S3 nanosheets via reflux method, followed by fabricating heterojunctions through a self-assembling process driven by coulombic force. Photocatalytic activity was evaluated under visible light, and photoelectrochemical measurements were conducted to analyze charge separations.

2：Sample Selection and Data Sources:

Samples included pristine La2Ti2O7, In2S3, their physical mixtures, and heterojunctions with varying mass ratios (

3：

4：0 to

1.0). Data were sourced from material characterizations and performance tests.

5：0). Data were sourced from material characterizations and performance tests. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment included X-ray diffractometer (Bruker D8 Focus), SEM (Hitachi S4800), TEM (JEOL JEM-2100), UV-Vis spectrophotometer (JASCO-750), BET surface area analyzer (Micromeritics TriStar 3000), FT-IR (Thermo Scientific NICOLET IS10), XPS (Thermo Escalab 250), Raman spectrograph (Renishaw inVia), photocatalytic reactor (Perfect Light Labsolar-IIIAG), Xenon lamp (Perfect Light PLX-SXE300), gas chromatograph (TECHCOMP GC7900), and electrochemical workstation (Zahner). Materials included La(NO3)3·xH2O (Aladdin, 99%), Ti(SO4)2 (Aladdin, 99.99%), In(NO3)3·4H2O, CTAB, TAA, DMF, Na2S, Na2SO3, H2PtCl6, FTO glass, and electrolytes.

6：99%), In(NO3)3·4H2O, CTAB, TAA, DMF, Na2S, Na2SO3, H2PtCl6, FTO glass, and electrolytes. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: Synthesis of nanosheets, fabrication of heterojunctions by mixing suspensions in DMF, calcination, characterization via XRD, SEM, TEM, UV-Vis, BET, FT-IR, XPS, Raman, photocatalytic H2 evolution tests with Pt co-catalyst, and PEC measurements in a three-electrode setup.

7：Data Analysis Methods:

Data were analyzed using software suites for spectroscopy, BET model for surface area, and statistical methods for photocatalytic rates and PEC data.