All the photocatalytic measurements were conducted in custom designed top-irradiation-type glass photoreactors with a screw-top cap equipped with a quartz window (Supplementary Fig. ). 10 mL of H2O or other water source were added to the photoreactor. The liquid was purged with N2 (containing 2% CH4 for gas chromatographic analysis) for 30 min. All purging needle holes were then sealed with Loctite superglue Universal adhesive. The prepared floating photocatalyst sheets were then placed on the surface of the liquid (n.b., the submerged photocatalyst sheets were placed directly in the liquid), and the headspace of the photoreactor was purged with the same N2/CH4 mixture for 15 min. The sheets were then irradiated by a solar light simulator (G2V Sunbrick LED Solar Simulator) calibrated to match air mass 1.5 global (AM 1.5G) irradiance. Light irradiation was calibrated 10-100 mW cm -2 with a certified Newport 843-R optical power meter. The experiments were conducted without stirring and temperature control. Gas chromatography was used to measure H2 evolution at set times (0, 2, 4, 8, 22 h). At each sampling time, 50 μL of gas sample was taken from the headspace of the photoreactors and analyzed using a Shimadzu GC-2010 Plus gas chromatograph with a barrier discharge ionization detector. To avoid any aerobic leakage, Separate O2 quantification were performed inside a UniLab glovebox under an inert atmosphere. The O2 evolution was monitored by a NeoFox-GT fluorometer and Fospor-R fluorescence oxygen sensor probe from Ocean Optics. The H 2 :O 2 ratio was calculated from accumulated gas after 22 h of experiment. For the long-term experiment, the reactor was purged with N2/CH4 mixture for 15 min before starting each cycle (no washing or substrate change was performed between cycles). For integrated setup, the 11 cm -2 SVG-PC sheets were tested in a 3D-printed reactor (Supplementary Fig. ). The reactor was printed using CPE+ (co-polyester) filament with UV-transmitting Plexiglass attached to the top part of the cell using two-part epoxy. The 25 cm -2 SVG-PC sheet was tested in a custom-made, one-compartment PEC reactors (Fig. ).