Hierarchical Active Site Engineering in Multicore–Shell nTiO ₂ @SiO ₂ Nanoreactors with PtSA–PtAC Synergy for Enhanced Solar Hydrogen Evolution

Abstract To address the persistent challenge of low solar‐to‐hydrogen (STH) conversion efficiency, it is presented a hierarchical active site engineering strategy via multiscale spatial confinement, implemented in multicore–shell nTiO ₂ @SiO ₂ nanoreactors. This architecture integrates structural confinement and atomic‐level Pt speciation to form a unified, multiscale catalytic system. Unlike conventional single‐core yolk–shell architectures, the interconnected multicore framework enhances light harvesting through internal multiple light‐scattering and effectively suppresses nanocore aggregation. Simultaneously, Pt single atoms and atomic clusters (Pt _SA+C ) are confined within the nanoreactors, forming atomically defined heterointerfaces with the TiO ₂ nanocores. This dual‐scale confinement significantly promotes charge separation and accelerates the hydrogen evolution reaction. As a result, the optimized 0.25 wt.%Pt _SA+C /nT@S catalyst achieves a hydrogen evolution rate of 73.8 mmol g ⁻¹ h ⁻¹ under simulated sunlight—a tenfold increase over Pt _NP /TiO ₂ —and delivers an apparent quantum efficiency (AQE) of 21.1% at 380 nm. This work establishes a generalizable cross‐scale confinement strategy that bridges nanostructure engineering with single‐atom catalysis, offering a robust platform for efficient solar hydrogen production and plastic photoreforming.