  Low-dose nitrogen implantation induces in TiO2 nanotubes a co-catalytic
activity for photocatalytic H2-evolution. The use of an ion implantation
process leads to a N-implanted zone only at the top part of the tubes. The
coupling of this top layer and the underlying non-implanted part of the
nanotubes strongly contributes to an efficient carrier separation and thus to a
significantly enhanced H2 generation.
