1：Experimental Design and Method Selection:

A one-step solvothermal method was used to synthesize Pt/Pt-Fe2O3 nanoplates with varying amounts of H2PtCl

2：The method involves reducing chloroplatinic acid with ethanol under high temperature and pressure to incorporate Pt2+ into α-Fe2O3 lattice and deposit Pt nanoparticles on the surface. Sample Selection and Data Sources:

Samples were prepared with 0,

3：05, 1, and 2 ml of H2PtCl6 (4g L-1), named as α-Fe2O3, Pt/Pt-Fe2O3-05, Pt/Pt-Fe2O3-1, and Pt/Pt-Fe2O3-2 NPs. Pt/Fe2O3 NPs were prepared as a contrast using as-prepared α-Fe2O3 NPs and H2PtClList of Experimental Equipment and Materials:

Equipment includes X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse-reflectance spectrometer (UV-vis DRS), photoelectrochemical cell (PEC) setup with three-electrode system, and gas chromatography for O2 evolution measurement. Materials include H2PtCl6, ethanol, CoOx nanoparticles as cocatalysts, and other chemicals for synthesis.

4：Experimental Procedures and Operational Workflow:

Solvothermal synthesis was performed at high temperature and pressure. Characterization involved XRD for phase identification, SEM/TEM/HRTEM for morphology and structure, XPS for chemical states, UV-vis DRS for optical properties, photocurrent and open circuit potential measurements for carrier separation, and photocatalytic O2 evolution tests under visible light irradiation with CoOx cocatalysts.

5：Data Analysis Methods:

XRD patterns were indexed to standard JCPDS cards. XPS spectra were analyzed for binding energy shifts. UV-vis DRS data were used with Tauc plots to determine band gaps. Photocurrent and Mott-Schottky plots were analyzed to calculate donor densities and Debye lengths. O2 evolution rates were measured and quantum yields calculated.