Industrial-Scale Engineering of Nano {RuO<sub>2</sub>/TiO<sub>2</sub>} for Photocatalytic Water Splitting: The Distinct Role of {(Rutile)TiO<sub>2</sub>–(Rutile)RuO<sub>2</sub>} Interfacing
Maria Solakidou, Areti Zindrou, Szymon Smykała, Yiannis Deligiannakis
Abstract
Photocatalytic RuO 2 /TiO 2 nanohybrids have been engineered using flame spray pyrolysis (FSP) technology, enabling the selective formation of either {(rutile)TiO 2 –(rutile)RuO 2 } or {(anatase)TiO 2 –(rutile)RuO 2 } nanointerphase in a single step. The {(rutile)TiO 2 –(rutile)RuO 2 } nanohybrids were selectively produced by using a double-nozzle FSP (DN-FSP) process. The {(anatase)TiO 2 –(rutile)RuO 2 } nanohybrids were selectively produced using a single-nozzle FSP (SN-FSP) process. Both RuO 2 /TiO 2 nanohybrids exhibited significant photocatalytic H 2 and O 2 production from H 2 O. Notably, the {(rutile)TiO 2 –(rutile)RuO 2 } is shown to be a superior photocatalyst, achieving H 2 evolution rates exceeding 5144 μmol g –1 h –1 H 2 and 2369 μmol g –1 h –1 O 2 under solar light illumination. This performance is 50% higher than that of the {(anatase)TiO 2 –(Rutile)RuO 2 } configuration. In situ EPR spectroscopy reveals that stable Ti 3+ /Ru 5+ centers are formed during the FSP process, in the {(rutile)TiO 2 –(rutile)RuO 2 } interphase. This highlights a unique interfacial electron-transfer event, which is ascribed to a strong oxide (RuO 2 )/support (TiO 2 ) 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–RuO 2 and the TiO 2 semiconductor, which is beneficial for the separation of interfacial electron–hole pairs onto TiO 2 and RuO 2 particles. Double-nozzle FSP technology, as demonstrated in this study, offers a promising engineering approach for the industrial production of high-efficiency photocatalytic materials.