Topotactic Epitaxy of SrTiO3 Mesocrystal Superstructures with Anisotropic Construction for Efficient Overall Water Splitting

The higher‐order structures of semiconductor‐based photocatalysts play crucial roles in their physicochemical properties for efficient light‐to‐energy conversion. A novel perovskite SrTiO3 mesocrystal superstructure with well‐defined orientation of assembled cubic nanocrystals was synthesized by topotactic epitaxy from TiO2 mesocrystals through a facile hydrothermal treatment. The SrTiO3 mesocrystal exhibits three times the efficiency for the hydrogen evolution of conventional disordered systems in alkaline aqueous solution. It also exhibits a high quantum yield of 6.7 % at 360 nm in overall water splitting and even good durability up to 1 day. Temporal and spatial spectroscopic observations revealed that the synergy of the efficient electron flow along the internal nanocube network and efficient collection at the larger external cubes produces remarkably long‐lived charges for enhanced photocatalysis. SrTiO3‐Mesokristall‐Überstrukturen sind leicht durch topotaktische Epitaxie von TiO2‐Mesokristallen in einem Hydrothermalverfahren aufzubauen. Der effiziente Elektronenfluss im Inneren des SrTiO3‐Nanowürfels sowie die effiziente Sammlung an den größeren äußeren Würfeln sorgen für bemerkenswert langlebige Ladungen und eine verbesserte Photokatalyse.