Unique Layered Tin Oxide Structure Via Buffered Anodization

The electrochemical anodization of various metals (e.g., Al [1], Ti [2] and Fe [3]) is able to generate a great variety of nanostructures. In the last decade, these new nanomaterials have received intensive interest due to their high technological potential in many applications such as photocatalysts for organic degradation [4], self-cleaning substrates [5] and solar cell electrodes [6, 7].

Tin dioxide (SnO₂) is an n-type semiconductor used as solid-state gas sensor [8] and oxidation catalyst [9]. It also has the potential to function as high capacity anode material for lithium-ion batteries [10]. Jeun et al. [11] synthesized irregular nanoporous tin oxide films in 0.3 M oxalic acid solution at 6 V and used it as a gas sensor material.

Anodization of tin in oxalic acid solutions at an applied voltage of above 5 V produces highly porous tin oxide structures. Lower applied voltages, as investigated by Yang et. Al [12], result in a passivation of the surface by precipitation of tin-oxalate.

We investigated the use of a buffer solution to prevent the precipitation of tin oxalate unto the surface. This enabled us to anodize tin at lower applied voltages resulting in a completely new tin / tin dioxide layer structure.

After optimizing the parameters, we investigated the growth mechanism and various chemical, physical and biological applications of this new structure.

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