Freestanding SnO2 films produced with anodic polarization in acidic media containing colloidal tin hydroxides

Akyil C., Akdas G., Afsin P., Urgen M. K.

MATERIALS CHEMISTRY AND PHYSICS, vol.221, pp.263-271, 2019 (SCI-Expanded) identifier identifier


Within the scope of the study, we aimed to develop a strategy for production of thick self -supporting tin oxide films with high surface area by anodic oxidation of metallic tin in acidic solutions. This has not been achieved before because of the highly porous and non-adherent nature of the oxidation products and high dissolution rate of tin in acidic solutions. Entrapment of the gelatinous colloidal tin hydroxides in the film during anodic oxidation exerted the necessary effect for decreasing the permeability of the oxide and dissolution of tin. Below this adherent and semi permeable film, a tin ion supersaturated zone was created, enabling the whisker type growth of complex tin oxyhydroxides at the metal/oxide interface. Colloidal + 4 valent acid insoluble tin hydroxides are prepared by oxidation of dissolved Sn+2 ions in sulfuric acid solution with H2O2. Moreover by utilizing this approach growing 100-150 mu m thick layers was possible, which were easily detached as free standing film from the underlying tin anode. The structure, chemistry and morphology of the films produced by anodic oxidation in acidic solutions were determined by using micro Raman spectroscopy, X-Ray diffraction (XRD) and SEM. Since the films produced by the above stated method consisted of a complex mixture of oxides, hydroxides and sulfates, annealing treatment was applied to convert these structures into stoichiometric SnO2.