1：Experimental Design and Method Selection:

The study compared three synthesis methods for CDs/ZIS nanocomposites: one-pot hydrothermal method (ZIS-H), hydrothermal deposition method (ZIS-HD), and stirring method (ZIS-S). The rationale was to evaluate how these methods affect morphology, photoelectric properties, and photocatalytic performance. Theoretical models included characterization of band structures and electron transfer mechanisms.

2：Sample Selection and Data Sources:

Samples included pure ZIS and CDs/ZIS composites prepared by the three methods. CDs were synthesized from starch via hydrothermal method. Selection criteria focused on maintaining consistent raw material ratios (e.g., 0.03 g CDs per 1 mmol ZIS) to isolate the effect of synthesis method.

3：03 g CDs per 1 mmol ZIS) to isolate the effect of synthesis method. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment included SEM (Hitachi s-4800), TEM (JEOL JEM 2100 F), XRD (Bruker D8), UV–vis DRS (Perkin-Elmer Lambda950), XPS (Axis Ultra HAS), PL (Hitachi F-7000), BET surface area analyzer (BelsorpⅡ), electrochemical workstation (CHI760e), and gas chromatography. Materials included starch, ZnCl2, InCl3·4H2O, thioacetamide, deionized water, ethanol, Na2SO3, Na2S, and Nafion.

4：Experimental Procedures and Operational Workflow:

CDs were synthesized hydrothermally from starch. ZIS-H involved one-pot hydrothermal synthesis with precursors and CDs. ZIS-HD involved hydrothermal treatment of pre-synthesized ZIS with CDs. ZIS-S involved stirring pre-synthesized ZIS with CDs. Characterization steps included SEM/TEM for morphology, XRD for crystal structure, XPS for elemental analysis, UV–vis DRS for optical properties, PL for charge separation, and BET for surface area. Photoelectrochemical tests used a three-electrode system. Photocatalytic activity was evaluated in a quartz reactor under visible light (λ > 420 nm) with sacrificial agents, and H2 production was measured by gas chromatography.

5：Data Analysis Methods:

Data analysis included calculation of band gaps from Kubelka–Munk function, ID/IG ratios from Raman spectra, flat-band potentials from Mott-Schottky plots, and hydrogen evolution rates. Statistical analysis involved comparing performance metrics across samples.