Prior to PC deposition, the SVG was treated with silanization solution (2.5 vol% dichlorodimethylsilane (DCDMS) in hexane) to increase its hydrophobicity (Supplementary Fig. ). The resulting hydrophobicallytreated SVG displayed a higher contact angle than the untreated samples (Figs. , Supplementary Fig. ), and also showed better water repellency against water droplets than the untreated samples (Supplementary Video 1). As a result, our SVG-PC in artificial seawater obtained H2 evolution rate and solar-to-H2 (STH) efficiency of 17.8±2.2 mmol m -2 h -1 and 0.11±0.02%, respectively. The values obtained with SVG-PC were ~3 times higher than those obtained with Glass-PC for liquid-phase seawater splitting (Fig. ). In contrast to the Glass-PC, near stoichiometric H2 and O2 evolution was achieved in seawater by SVG-PC (Fig. , Supplementary Table ). The H 2 evolution rates of SVG-PC over pure water and seawater were also linear throughout the photocatalytic tests (Supplementary Fig. , Supplementary Table ). A control experiment confirmed that when SVG-PC sheets were irradiated with only Vis-IR, the sheets do not yield any H2. On the other hand, the performance of the sheets was reduced by half without the photothermal effect from the SVG (UV irradiation only, see Supplementary Fig. , Supplementary Table ). Under this irradiation condition, the sheets maintained a reasonable performance as the vapour generation rate was still enhanced by the SVG (Supplementary Fig. , Supplementary Table ). Further control experiments under full spectrum irradiation showed that without the direct interaction between the SVG and the liquid phase, the H2 evolution of SVG-PC decreased by an order of magnitude (Supplementary Fig. , Supplementary Table ). This indicates that localized heating at the liquid-vapour interface by the SVG was crucial for the optimal function of SVG-PC by maintaining a high flux of water vapour over the photocatalyst. The photothermal effect of the SVG was visualized using infrared thermal imaging, which shows a higher local temperature on the SVG compared to the bulk liquid (Supplementary Figs. , Supplementary Video 2). These results confirm the synergistic effect of the hybrid photothermalphotocatalyst design for full solar spectrum utilization.