1：Experimental Design and Method Selection:

The study involved designing a benthic microbial fuel cell (BMFC) with a photocatalytic cathode. The photocathode was fabricated by electrodepositing Cu2O on carbon felt and coating it with a carbon layer. Photoelectrochemical tests and BMFC performance evaluations were conducted under light and dark conditions.

2：Sample Selection and Data Sources:

Natural seawater and marine sediment were collected from Mazi Port, Weihai, China. Carbon felt electrodes were used, with specific dimensions for anodes and cathodes.

3：List of Experimental Equipment and Materials:

Equipment included an electrochemical workstation (CHI660E, Chenhua Instruments Co., Ltd., China), X-ray diffraction spectrometer (XRD, DX-2700, Dandong Haoyuan instrument co., LTD), field emission scanning electron microscope (FESEM, Merlin Compact, Carl Zeiss Microscopy), digital multimeter (Keithley 2700, American Tektronix corporations), and a white light LED lamp (50 W, Taiming photoelectric Co., Ltd). Materials included carbon felt (Sanye Carbon Co., Ltd. China), CuSO4, tartaric acid, NaOH, glucose, and others.

4：Experimental Procedures and Operational Workflow:

The BMFC was set up with sediment and seawater. Electrodes were prepared and treated. Electrodeposition of Cu2O was performed at 80°C with varying deposition times, followed by carbon layer coating. Characterization involved SEM, XRD, and photoelectrochemical tests. BMFC performance was measured using polarization curves, EIS, and photocurrent-time curves.

5：Data Analysis Methods:

Data were analyzed using linear sweep voltammetry, EIS fitting to equivalent circuits, and statistical methods with triplicate runs and relative standard deviation less than 10%.