The influence of water-induced crystallization on the photoelectrochemical properties of porous anodic tin oxide films

Tuning the Photoelectrochemical Properties of Narrow Band Gap Nanoporous Anodic SnOx Films by Simple Soaking in Water

“…After long-term exposure to water, the pores are almost completely clogged with a secondary deposit having highly granular morphology ( Figure 1 C,D). As we discussed in detail previously [ 19 ], these changes are a result of dissolution–redeposition processes. However, as can be seen in Figure 1 D, even after 120 h of soaking, the porous morphology is still present within the internal part of the layer.…”

“…However, as can be seen in Figure 1 D, even after 120 h of soaking, the porous morphology is still present within the internal part of the layer. Contrary to this, we recently showed that after soaking for the same time, anodic SnO x films grown at 2 V were found to be almost completely compact [ 19 ]. This discrepancy could be attributed to much wider channels within the layers grown at higher potentials (see above).…”

“…As already mentioned, directly after the anodization process, oxide film layers are amorphous and independent of the applied voltage or electrolyte type [ 1 , 7 , 19 ]. On the contrary, XRD patterns obtained for the materials stored in water ( Figure 2 ) exhibit noticeable maxima located at 26.6°, 34.1°, 37.6°, 51.8°, and 66.1° that can be attributed to the cassiterite SnO 2 phase.…”

“…Therefore, in the literature, a new strategy based on increasing the degree of crystallinity by simple storage in water has emerged. Water-enabled crystallization has been mainly studied for anodic TiO 2 layers [ 13 , 14 , 15 , 16 , 17 ] up to 2017 when Bian and co-workers transferred these considerations to anodic tin oxide [ 18 ]; also, in our recent work [ 19 ], we verified the influence of soaking in water on the morphology, structure, and photoelectrochemical properties of anodic SnO x layers obtained via potentiostatic anodization in the alkaline electrolyte at the potential of 2 V. We confirmed that exposure to water contributes to phase transformation from amorphous into the rutile type SnO 2 by dissolution–redeposition process what significantly affects the morphology of the material. In particular, with prolonged immersion time, deterioration of the porous form of anodic layers occurred, and structure became less defective.…”

“…In particular, with prolonged immersion time, deterioration of the porous form of anodic layers occurred, and structure became less defective. Such changes contributed to the widening of the bandgap and dramatic decrease of the photoelectrochemical performance of the material [ 19 ].…”