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

Abstract

Nanoporous tin oxide layers obtained via anodic oxidation of metallic tin at the potential of 4 V in the alkaline electrolyte (1 M NaOH) were soaked in distilled water for various durations (from 2 h to 120 h) to verify the influence of water-enabled crystallization on the morphology, composition, and related optical and photoelectrochemical properties of such kind of anodic SnOx. Although water soaking generally contributes to more stoichiometric and crystalline tin oxide, it was confirmed that at the initial stages of the water-induced dissolution–redeposition process, material exhibits enhanced photoelectrochemical performance under simulated sunlight irradiation. However, long-time exposure to water results in a gradual widening of the material’s band gap, shifting of the photoelectrochemical spectra towards higher energies, and almost complete deterioration of the photoelectrochemical activity under sunlight irradiation.

Improving the photoelectrochemical performance of porous anodic SnO x films by adjusting electrosynthesis conditions

“…Labels of particular samples refer to anodizing conditions listed in Table 3 comparison of the band alignment can be drawn from the measurements carried out under the same conditions. Moreover, the E g value obtained for the sample B10 is much higher than those typically observed for thicker anodic SnO x films grown by anodization at 4 V, 30,37,50 mainly due to the limited thickness of the anodic film (see above). However, the narrower E g would result in an even more favorable band alignment in bA and Ba photoanodes (less positive E VB facilitating the hole transport to the electrode surface).…”

CdS-Decorated Porous Anodic SnOx Photoanodes with Enhanced Performance under Visible Light

“…For photoanodes based on anodically generated nanoporous tin oxide films, numerous challenges have to be overcome, from choosing appropriate electrosynthesis conditions for obtaining continuous nanostructures [ 15 ] to non-stoichiometric compositions of this kind of film [ 12 , 14 ]. Different strategies, including controlled thermal treatment [ 12 , 14 ], crystallization in water [ 16 , 17 ], and decoration with other semiconductors [ 18 , 19 , 20 ], have already been proposed to optimize the photoelectrochemical performance of tin oxide films. Among them, the latter approach, based on the deposition of different narrow band gap semiconductors on the tin oxide nanostructures, is considered especially promising since it results in enhanced absorption of the visible light and facilitates the charge carriers’ separation due to the favorable band alignment.…”