ABSTRACT
Anodic oxides are those oxides synthesized electrochemically by oxidation of a metallic substrate in a suitable electrolyte. The titanium dioxide nanotubes (TiO2-NT) arrays are one of the most famous representative materials of this class. The anodic oxidation of metal is a process known as “anodization”, a facile and scalable surface treatment method beneficial for producing nanostructured films on metal substrates with precise control of morphology and composition. Since it is based on an electrochemical process that utilizes mild temperature conditions and non-toxic reagents, it is also considered an environmentally friendly technique for fabricating metal oxides with high surface area and unidirectional orientation. Furthermore, the low cost and chemical stability make the anodized nanostructured oxides attractive for several applications in the energy sector, especially as components of dye-sensitized solar cells, photoelectrochemical water-splitting systems, fuel cells, supercapacitors, and batteries. Herein, we describe the main uses of nanostructured anodic oxides in these applications, from the widely employed TiO2-NT to the nanostructured Fe2O3, NiO, CuxO, ZnO, WO3, Nb2O5, Ta2O5, and SnO2 films.
