1：Experimental Design and Method Selection:

The study involved the synthesis of BiNPs decorated BiVO4/rGO photoanode for PEC water splitting. The chemical stability and plasmonic behavior of BiNPs were improved by rGO surface.

2：Sample Selection and Data Sources:

Bismuth acetate, bismuth nitrate trihydrate, acetic acid, sodium borohydride, ethanol, concentrated sulphuric acid, graphite powder, sodium nitrate, potassium permanganate, hydrogen peroxide, acetylacetone, vanadyl acetylacetonate, hydrochloric acid were used as materials.

3：List of Experimental Equipment and Materials:

Shimadzu UV-3600 instrument for UV-Vis spectra, PANalytical XpertPRO diffractometer for XRD, FESEM (Zeiss supra 40) for surface morphologies, HR-TEM (TECNAI G-2 FEI) for TEM images, LOT-Oriel with a 150 W Xe for linear sweep voltammetric studies, Autolab PGSTAT 302 N for chronoamperometric studies, EIS, and CV, Oriel IQE-200 instrument for IPCE data, Trace-1310 GC for hydrogen gas quantification.

4：Experimental Procedures and Operational Workflow:

BiNPs were synthesized by chemical reduction method, rGO by Hummer’s method. The fabrication of photoelectrodes was done by drop-casting. PEC measurements were performed in a three-electrode system in 0.1 M Na2SO4 solution.

5：1 M Na2SO4 solution. Data Analysis Methods:

5. Data Analysis Methods: The approach for analyzing experimental data included statistical techniques and software tools utilized in the instruments mentioned.