Industrial-Scale Engineering of Nano {RuO₂/TiO₂} for Photocatalytic Water Splitting: The Distinct Role of {(Rutile)TiO₂-(Rutile)RuO₂} Interfacing

Photocatalytic RuO₂/TiO₂ nanohybrids have been engineered using flame spray pyrolysis (FSP) technology, enabling the selective formation of either {(rutile)TiO₂-(rutile)RuO₂} or {(anatase)TiO₂-(rutile)RuO₂} nanointerphase in a single step. The {(rutile)TiO₂-(rutile)RuO₂} nanohybrids were selectively produced by using a double-nozzle FSP (DN-FSP) process. The {(anatase)TiO₂-(rutile)RuO₂} nanohybrids were selectively produced using a single-nozzle FSP (SN-FSP) process. Both RuO₂/TiO₂ nanohybrids exhibited significant photocatalytic H₂ and O₂ production from H₂O. Notably, the {(rutile)TiO₂-(rutile)RuO₂} is shown to be a superior photocatalyst, achieving H₂ evolution rates exceeding 5144 μmol g^-1 h^-1 H₂ and 2369 μmol g^-1 h^-1 O₂ under solar light illumination. This performance is 50% higher than that of the {(anatase)TiO₂-(Rutile)RuO₂} configuration. In situ EPR spectroscopy reveals that stable Ti³⁺/Ru⁵⁺ centers are formed during the FSP process, in the {(rutile)TiO₂-(rutile)RuO₂} interphase. This highlights a unique interfacial electron-transfer event, which is ascribed to a strong oxide (RuO₂)/support (TiO₂) interaction (SOSI), further validated by transmission electron microscopy/scanning transmission electron microscopy. From a technological perspective, FSP fosters a robust {rutile-rutile} interface between the semimetal-RuO₂ and the TiO₂ semiconductor, which is beneficial for the separation of interfacial electron-hole pairs onto TiO₂ and RuO₂ particles. Double-nozzle FSP technology, as demonstrated in this study, offers a promising engineering approach for the industrial production of high-efficiency photocatalytic materials.