Optimal interface structure in anatase–rutile mixed TiO2 for enhanced charge separation and prolonged carrier lifetime

The carrier lifetime in the anatase–rutile mixed TiO2 spans different time scales in experiments—from values close to those of pure TiO2 (∼1 ns) up to ∼20 ns—and correspondingly, photocatalytic activities also vary widely. However, the origin of this variability remains unclear. Here, using our recently developed interface structure prediction method, ML-interface, we identify three atomic-matched interfaces between anatase and rutile. Nonadiabatic molecular dynamics calculations reveal that electron transfer across all three interfaces is rapid, occurring within 33 fs. In contrast, the carrier recombination lifetimes of the interfaces span 1.9–26.2 ns, indicating the importance of interface structures. Notably, the (114)Anatase//(21̄1)Rutile interface exhibits the longest carrier recombination lifetime (∼26 ns), thereby benefiting the photocatalytic activity. These findings demonstrate that optimal photocatalytic performance arises from deliberate engineering of interface structures, rather than from simple mixing of anatase and rutile phases.