1：Experimental Design and Method Selection:

The study employed magnetron reactive sputtering for thin-film deposition due to its ability to produce high-quality, uniform films at high growth rates. Annealing in O2 ambient was used to stabilize the structure and improve crystallinity.

2：Sample Selection and Data Sources:

F-doped SnO2 transparent conducting glass (FTO) was used as the substrate. Samples were prepared with different annealing conditions (no annealing, rapid thermal annealing at 500°C, slow rate annealing at 300°C and 500°C).

3：List of Experimental Equipment and Materials:

Equipment includes magnetron sputtering system, annealing furnace, ultrasonic cleaner, X-ray diffractometer (XRD, D/max-500, Rigaku Co.), Raman spectrometer (InVia Confocal Raman Microscope, Renishaw), scanning electron microscope (SEM, Ultra 55, Zeiss), atomic force microscope (AFM), X-ray photoelectron spectrometer (XPS, PHI 5000 Versa Probe, ULVAC-PHI, INC.), UV-Vis spectrophotometer (TU-1901, PERSEE), electrochemical workstation (CHI660D, Shanghai Chenhua Instrument Co., Ltd.), Xe lamp (PLS-SXE300, Beijing Changtuo Co., Ltd.). Materials include acetone, ethanol, deionized water, Ar and O2 gases, Cu and W targets (

4：99% purity), Na2SO4 electrolyte. Experimental Procedures and Operational Workflow:

The FTO substrate was cleaned ultrasonically. CuOx was deposited first by sputtering Cu target in Ar/O2 atmosphere, followed by WO3 deposition using W target. Annealing was performed under specified conditions. Photoelectrodes were fabricated by connecting copper wire to FTO. Characterization involved XRD, Raman, SEM, AFM, XPS, UV-Vis, and photoelectrochemical tests using a three-electrode system with Pt counter electrode and Ag/AgCl reference electrode in Na2SO4 electrolyte under light illumination.

5：Data Analysis Methods:

Data were analyzed using techniques such as Kubelka-Munk function for bandgap calculation, Mott-Schottky plots for carrier concentration and flat band potential, and equivalent circuit fitting for electrochemical impedance spectroscopy (EIS).