Alkali Induction Strategy for Artificial Photosynthesis of Hydrogen by TiO₂ Heterophase Homojunctions

The robust separation and utilization of photogenerated electrons-holes (e⁻-h⁺) are key in accelerating redox reactions. Unlike traditional heterojunction photocatalysts, homojunction features different energy bandgaps with interchangeable compositions that can significantly trigger charge carrier dynamics, but their precise construction remains an ongoing challenge owing to quick lattice-level modulations. Herein, TiO₂-based homojunction (HT_M-OH) holding dissimilar yet discernible crystalline phases (anatase and rutile) are rationally constructed by a straightforward alkali-induced strategy which enables controllable lattice-transition/orientation. The resulting HT_M-OH exhibits speedy separation and well-guided flow of e⁻-h⁺ over redox sites with extended carrier lifetime, leading to high-rate hydrogen generation (HER, 34.35 mmol g⁻¹ h⁻¹) under simulated sunlight. Moreover, a self-made thin film of HT_M-OH indicates a notable scale-up potential under real-time sunlight. This work furnishes a new non-complex homojunction strategy for speeding charge carrier kinetics, credibly extendable to a diverse range of catalysts and applications.