  Photocatalytic $H_2$ evolution reactions on pristine TiO$_2$ is characterized
by low efficiencies due to trapping and recombination of charge carriers, and
due to a sluggish kinetics of electron transfer. Noble metal (mainly Pt, Pd,
Au) nanoparticles are typically decorated as cocatalyst on the TiO$_2$ surface
to reach reasonable photocatalytic yields. However, owing to the high cost of
noble metals, alternative metal cocatalysts are being developed. Here we
introduce an approach to fabricate an efficient noble metal free photocatalytic
platform for $H_2$ evolution based on alloyed NiCu cocatalytic nanoparticles at
the surface of anodic TiO$_2$ nanotube arrays. NiCu bilayers are deposited onto
the TiO$_2$ nanotubes by plasma sputtering. A subsequent thermal treatment is
carried out that leads to dewetting, that is, owing to surface diffusion the Ni
and Cu sputtered layers simultaneously mix with each other and split into NiCu
nanoparticles at the nanotube surface. The approach allows for a full control
over key features of the alloyed nanoparticles such as their composition, work
function and cocatalytic ability towards $H_2$ generation. Dewetted-alloyed
cocatalytic nanoparticles composed of equal Ni and Cu amounts not only are
significantly more reactive than pure Ni or Cu nanoparticles, but also lead to
$H_2$ generation rates that can be comparable to those obtained by conventional
noble metal (Pt) decoration of TiO$_2$ nanotube arrays.
