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.
Bibliographical noteFunding Information:
J.H.P. acknowledges the support by the NRF of Korea Grant funded by the Ministry of Science, ICT & Future Planning (2016R1A2A1A05005216, 2016M3D3A1A01913254, 2015M1A2A2074663). S.H.O. acknowledges the support for the TEM work by the Creative Materials Discovery Program (NRF-2015M3D1A1070672), Bio-inspired Innovation Technology Development Project (NRF-2018M3C1B7021994) through the National Research Foundation of Korea (NRF) of the Ministry of Science, the ICT and Future Planning, and Industrial Technology Innovation Program (10080654) of the Ministry of Trade, Industry & Energy (MOTIE, Korea). K.S.L. acknowledges support by the Nano-Material Fundamental Technology Development program (2017M3A7B4049173) through the National Research Foundation of Korea (NRF). K.Z. acknowledges support by “the Fundamental Research Funds for the Central Universities” (No. 30918011106).
© 2018 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanical Engineering