Ultrafast Photocatalytic Wettability Switching in Substrate‐Interface Tailored Titanium Dioxide Thin Films

ABSTRACT In this study, we investigate the ultrafast photocatalytic wettability switching in titanium dioxide (TiO 2 ) thin films, tailored at the substrate‐interface level. We explore the effects of silicon substrate doping and the introduction of interface oxides on the photocatalytic contact angle switching rate. Our findings demonstrate that higher silicon substrate doping levels decrease the active layer thickness, reducing the switching rate, while the presence of interface oxides enhances the switching rate by preventing electron‐hole pair transfer into the substrate. Additionally, we examine the photocatalytic liquid spreading effects on nanostructured TiO 2 surfaces, revealing that conformally TiO 2 coated silica nanostructures strongly support photocatalytic hemiwicking. These results are supported by theoretical predictions and provide insights into optimizing TiO 2 thin films for advanced photocatalytic applications.