Multiple Heterojunction in Single Titanium Dioxide Nanoparticles for Novel Metal-Free Photocatalysis

• Published in: Nano letters Vol. 18; no. 7; pp. 4257 - 4262
• Main Authors: Cho, Yoonjun, Kim, Sungsoon, Park, Bumsu, Lee, Chang-Lyoul, Kim, Jung Kyu, Lee, Kug-Seung, Choi, Il Yong, Kim, Jong Kyu, Zhang, Kan, Oh, Sang Ho, Park, Jong Hyeok
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 11.07.2018
• Subjects: surface reactivity; disorder engineering; multiple-heterojunction; charge separation; water splitting; Photocatalysts
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/acs.nanolett.8b01245

Despite a longstanding controversy surrounding TiO2 materials, TiO2 polymorphs with heterojunctions composed of anatase and rutile outperform individual polymorphs because of the type-II energetic band alignment at the heterojunction interface. Improvement in photocatalysis has also been achieved via black TiO2 with a thin disorder layer surrounding ordered TiO2. However, localization of this disorder layer in a conventional single TiO2 nanoparticle with the heterojunction composed of anatase and rutile has remained a big challenge. Here, we report the selective positioning of a disorder layer of controlled thicknesses between the anatase and rutile phases by a conceptually different synthetic route to access highly efficient novel metal-free photocatalysis for H2 production. The presence of a localized disorder layer within a single TiO2 nanoparticle was confirmed for the first time by high-resolution transmission electron microscopy with electron energy-loss spectroscopy and inline electron holography. Multiple heterojunctions in single TiO2 nanoparticles composed of crystalline anatase/disordered rutile/ordered rutile layers give the nanoparticles superior electron/hole separation efficiency and novel metal-free surface reactivity, which concomitantly yields an H2 production rate that is ∼11-times higher than that of Pt-decorated conventional anatase and rutile single heterojunction TiO2 systems.