1：Experimental Design and Method Selection:

The study used a two-step hydrothermal method to synthesize CdWO4 nanorods and CoNi2S4 nanoparticles, with tert-butyl alcohol (TBA) used to control the morphology of CoNi2S4 into spherical shapes. The rationale was to create a composite photocatalyst with enhanced surface area and charge transfer properties for hydrogen evolution under visible light.

2：Sample Selection and Data Sources:

Samples included pure CdWO4, pure CoNi2S4, and CoNi2S4/CdWO4 composites with different weight ratios (CNS/CW-1 to CNS/CW-5). Materials were sourced as chemical reagents without further purification.

3：5). Materials were sourced as chemical reagents without further purification. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment included a Teflon-lined autoclave for hydrothermal synthesis, XRD (Rigaku Smartlab) for crystal structure analysis, UV-2550 spectrophotometer for UV-vis DRS, SEM (ZEISS EVO 18) and TEM for morphology, BET analyzer (ASAP 2020M) for surface area, fluorescence spectrometer for PL spectra, gas chromatography (SP2100) for hydrogen measurement, and electrochemical workstation (CHI 660D) for photoelectrochemical tests. Materials included sodium tungstate dehydrate, cadmium nitrate, cobalt nitrate, nickel nitrate, thiourea, ammonium, tert-butyl alcohol, eosin Y, triethanolamine, and deionized water.

4：Experimental Procedures and Operational Workflow:

Synthesis involved dissolving precursors, hydrothermal reactions at 180°C for specified times, washing, and drying. Photocatalytic tests were conducted in a quartz bottle with a white light lamp, using eosin Y as a sensitizer and triethanolamine as a sacrificial agent, under anaerobic conditions. Electrodes were prepared by depositing catalyst suspensions on ITO glass.

5：Data Analysis Methods:

Data analysis included XRD for phase identification, UV-vis for band gap calculation using Eg=1240/λ, BET for surface area, PL for charge recombination, GC for hydrogen quantification, and electrochemical measurements (photocurrent, LSV, EIS) for electron transfer efficiency.