Crystal Facet Engineering and Hydrogen Spillover-Assisted Synthesis of Defective Pt/TiO2-x Nanorods with Enhanced Visible Light-Driven Photocatalytic Activity.

Hydrogen spillover can assist the introduction of defects such as Ti3+ and concomitant oxygen vacancies (VO) in a TiO2 crystal, thereby inducing a new level below the conduction band to improve the conductivity of photogenerated electrons and the visible light absorption property of TiO2. Meanwhile, crystal facet engineering offers a promising approach to achieve improved activity by influencing the recombination step of the photogenerated electrons and holes. In this study, with the aim of achieving enhanced visible light-driven photocatalytic activity, rutile TiO2 nanorods with different aspect ratios were synthesized by crystal facet engineering, and Pt-deposited TiO2-x nanorods (Pt/TNR) were then obtained via reduction treatment assisted by hydrogen spillover. The reduction treatment at 200 °C induced the formation of surface Ti3+ exclusively, whereas surface Ti3+ and VO were formed by performing the reduction at 600 °C. The Pt/TNR with a higher aspect ratio reduced at 200 °C exhibited the highest activity in photocatalytic H2 production under visible light irradiation owing to the synergistic effect of the introduction of Ti3+ defects and the spatial charge carrier separation induced by crystal facet engineering.

Isomerizations of a Pt4 cluster revealed by spatiotemporal microscopic analysis.

We now report the first direct observation of the fluxional nature in which the four-atomic platinum cluster (Pt4) randomly walks through several isomers. Time-lapse analysis by a Cs-corrected transmission electron microscope allowed us to acquire the atomic coordinates at a sub-angstrom space resolution and 0.2 s time resolution for each cluster isomer. The analysis revealed that the isomerization follows a simple first-order kinetic model.