Hierarchical 3D TiO ₂ Nanotube Arrays Sensitized by Graphene Oxide and Zn _x Cd _y S for High Performance Photoelectrochemical Applications

Photocatalysis and photoelectrocatalysis are highly promising for applications in the energy and environment sectors. Several photocatalytic devices based on TiO ₂ nanotubes grown on two-dimensional (2D) substrate (such as titanium foil) have been developed, but there has been little research on three-dimensional (3D) TiO ₂ nanotubes which are expected to offer significantly enlarged surface area and much improved photocatalytic efficiency. Here, a method of building 3D TiO ₂ nanotube arrays (3D-TNTAs) on titanium mesh by anodization via controlling the reaction time and electrolyte is reported. It is found that the electrochemically active area of such a titanium mesh is almost 4 times larger than that of the traditional titanium foil. Moreover, through making composites of graphene oxide and Zn _x Cd _y S onto 3D TiO ₂ nanotubes, hierarchical nanotube arrays (Zn _x Cd _y S/GO/3D-TNTAs) are made by calcination-deposition of graphene oxide followed by a facile successive ionic layer adsorption reaction (SILAR) treatment with Zn _x Cd _y S. Characterization of the Zn _x Cd _y S/GO/3D-TNTAs indicates that this hierarchical multi-layered nanostructure has a much improved photoelectrochemical property due to the enlarged surface area and improved electron–hole separation capability, demonstrating the great potential for applications in photoelectrocatalytic devices for environmental technologies.