Engineering of a N-Doped Anatase/Rutile TiO2 Heterophase Junction via In Situ Phase Growth for Photocatalytic Hydrogen Evolution

N-doped anatase/rutile TiO₂ (AR-N/TiO₂) photocatalysts were prepared by combining the strategy of N-doping and in situ heterophase junction generation, which significantly enhanced the photocatalytic H₂ generation (1.68 mmol· h^–1·g^–1). Under monochromatic light at 400 nm, the light exhibits an apparent quantum efficiency of 8.6%. Moreover, this AR-N/TiO₂ heterophase junction demonstrates excellent long-term stability when exposed to visible light irradiation. Through the analysis of the electronic structure, the outstanding photocatalytic activity of AR-N/TiO₂ can be attributed to the maximized synergetic effect between rutile and anatase for optimal rutile content (21.6%) and enhanced response to visible light due to N-doping. Additionally, the intimate interface formed by the rutile phase grown in situ from the inner core of the anatase phase establishes well-aligned bands, which promote efficient separation of photoinduced electron–hole pairs. Furthermore, the rough surface and porosity of the as-synthesized heterophase junction facilitate an enlarged specific surface area and exposure of active sites, thereby providing more adsorptive and reactive sites that enhance conversion efficiency. This research offers an alternative approach to phase engineering for developing TiO₂-based heterophase junction photocatalysts toward efficient hydrogen evolution.