Pt Single Atom Co‐Catalysts on Thin, Defined Anatase Layers: Critical Factors for Photocatalytic Hydrogen Generation

film and is sufficient to fully utilize the photogenerated electron flux under ultravoilet excitation. This work introduces the concept of a critical co-catalyst density that separates the transition from co-catalyst-limited to absorber-limited behavior in SAC-based photocatalysis, thereby contributing to a further rational design of photocatalytic systems.