TiO2-B/Anatase Core-Shell Heterojunction Nanowires for Photocatalysis

Fast separation and spatial control of electrons and holes after photogeneration is important in photocatalysis. Ideally, after photogeneration, electrons and holes must be segregated to different parts of the photo catalyst to take part in separate oxidation and reduction reactions. One way to achieve this is by building junctions into the catalyst with built-in chemical potential differences that tend to separate the electron and the hole into two different regions of the catalyst. In this work, we sought to accomplish this by controllably forming junctions between different phases of TiO2. A synthesis method has been developed to prepare TiO2-B core and anatase shell core shell nanowires. We control the anatase phase surface coverage on the TiO2-B core and show that the maximum photocatalytic activity is obtained when the solution containing the reactants can contact both the anatase and TiO2-B phases. The photocatalytic activity drops both with bare TiO2-B nanowires and with completely anatase covered TiO2-B nanowires. In contrast, nanowires partially covered with anatase phase gives the highest photocatalytic activity. The improved photocatalytic activity is attributed to the effective electron hole separation at the junction between the anatase and TiO2 B phases.