Abstract
In the present work we grow self-organized TiO
nanotube arrays with a defined and controlled regular spacing between individual nanotubes. These defined intertube gaps allow one to build up hierarchical 1D-branched structures, conformally coated on the nanotube walls using a layer by layer nanoparticle TiO
decoration of the individual tubes, i.e. having not only a high control over the TiO
nanotube host structure but also on the harvesting layers. After optimizing the intertube spacing, we build host-guest arrays that show a drastically enhanced performance in photocatalytic H
generation, compared to any arrangement of conventional TiO
nanotubes or conventional TiO
nanoparticle layers. We show this beneficial effect to be due to a combination of an increased large surface area (mainly provided by the nanoparticle layers) with a fast transport of the harvested charge within the passivated 1D nanotubes. We anticipate that this type of hierarchical structures based on TiO
nanotubes with adjustable spacing will find even wider application, as they provide an unprecedented controllable combination of surface area and carrier transport.