1：Experimental Design and Method Selection:

The study involved synthesizing Zn1-xCdxS solid solutions via a precipitation method and depositing an ultra-thin NiO layer using an in-situ photodeposition method to create NiO/Zn0.8Cd0.2S composites. Theoretical models for charge separation and photocatalytic mechanisms were considered.

2：8Cd2S composites. Theoretical models for charge separation and photocatalytic mechanisms were considered. Sample Selection and Data Sources:

2. Sample Selection and Data Sources: Samples with varying Cd content (x=0, 0.1, 0.2, 0.5, 0.9, 1.0) and NiO loadings (1-20 wt%) were prepared. Data were sourced from laboratory experiments including photocatalytic activity tests and material characterizations.

3：1, 2, 5, 9, 0) and NiO loadings (1-20 wt%) were prepared. Data were sourced from laboratory experiments including photocatalytic activity tests and material characterizations. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment included X-ray diffractometer (X'pert Philips PRO), X-ray photoelectron spectrometer (ESCALAB 250Xi), BET surface area analyzer (Micromeritics ASAP 2020M), transmission electron microscope (Tecnai-G2-TF20), UV-vis spectrophotometer (Shimadzu UV-2550), photoluminescence spectrometer (Edinburgh FL/FS900), gas chromatograph (Agilent 6820), and electrochemical workstation (CHI 660E). Materials included cadmium chloride, zinc acetate, sodium sulfide, nickel acetate, methanol, sodium sulfate, deionized water, and others as specified.

4：Experimental Procedures and Operational Workflow:

Zn1-xCdxS was synthesized by mixing metal salts with NaOH and Na2S, aging, washing, and drying. NiO was photodeposited by suspending Zn0.8Cd0.2S in a solution with nickel acetate and methanol, irradiating with a Xe lamp (300 W, λ≥420 nm), and collecting the product. Photocatalytic tests involved dispersing catalyst in water, degassing with Ar, irradiating with visible light, and measuring H2 evolution. Characterizations included XRD, XPS, BET, TEM, UV-vis DRS, PL, and electrochemical measurements.

5：8Cd2S in a solution with nickel acetate and methanol, irradiating with a Xe lamp (300 W, λ≥420 nm), and collecting the product. Photocatalytic tests involved dispersing catalyst in water, degassing with Ar, irradiating with visible light, and measuring H2 evolution. Characterizations included XRD, XPS, BET, TEM, UV-vis DRS, PL, and electrochemical measurements. Data Analysis Methods:

5. Data Analysis Methods: Data were analyzed using techniques such as XRD peak indexing, XPS binding energy calibration, BET surface area calculation, TEM image analysis, UV-vis absorption edge determination, PL lifetime fitting, and electrochemical impedance fitting with equivalent circuits.