Achieving Multiswitchable Phases to Govern Enhanced Photocatalysis in Staggered <scp> In ₂ Se ₃ </scp> / <scp>SnSe</scp> Heterostructure

Two‐dimensional staggered heterostructures, featuring by the intrinsically facilitate charge separation, provide promising platforms for efficient photocatalytic water splitting. However, their carrier dynamics generally follow two competing pathways: type II and Z‐scheme, with the distinct governing mechanisms in photocatalysis remain elusive. Here, through stacking or sliding ferroelectric control, we realize three switchable phases within an In 2 Se 3 /SnSe heterostructure, and uncover how interlayer polarization governs carrier dynamics for enhanced photocatalytic activities and efficiencies. First‐principle results show that transitions between type II and Z‐scheme models can be driven by the reversal of interlayer electric fields () or donor–acceptor band edge exchanges, which will further modulate their carrier separation, redox potential alignment, interlayer carrier lifetime, carrier dynamics, spontaneous thermodynamic feasibility, and energy conversion efficiency. Compared with the inactive type II (↑ Se − ) phase, strengthened in the type‐II (↓ Se − ) phase suppresses interlayer e–h recombination to prolonged carrier lifetimes, while the Z‐scheme (↓ Sn + ) accelerate this recombination, forming new active band edges. Thereby, both yield higher redox potentials for superior photocatalytic activities and efficiencies. These results uncover how stacking‐induced polarization defines carrier‐dynamics in staggered heterostructures, establishing interlayer engineering as an effective route toward next generation of switchable and high efficient 2D photocatalysts.