Formation of Nanoporous Tin Oxide Layers on Different Substrates during Anodic Oxidation in Oxalic Acid Electrolyte

Leszek Zaraska,Michał Bobruk,Grzegorz D Sulka

doi:10.1155/2015/302560

Leszek Zaraska, Michał Bobruk + Show 1 more

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https://doi.org/10.1155/2015/302560

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Abstract

Nanoporous tin oxide layers were obtained on various Sn substrates including high- and low-purity foils and wire by one-step anodic oxidation carried out in a 0.3 M oxalic acid electrolyte at various anodizing potentials. In general, amorphous oxide layers with the atomic ratio of Sn : O (1 : 1) were grown during anodization, and a typical structure of the as-obtained film consists of the “outer” layer with less regular, interconnetted pores and the “inner” layer with much more uniform and regular channels formed as a result of vigorous gas evolution. It was found that the use of electrochemical cell with the sample placed horizontally on the metallic support and stabilized by the Teflon cover, instead of the typical two-electrode system with vertically arranged electrodes, can affect the morphology of as-obtained layers and allows fabrication of nanoporous oxides even at anodizing potentials up to 11 V. An average pore diameter in the “outer” oxide layer increases with increasing anodizing potential, and no significant effect of substrate purity on the structure of anodic film was proved, except better uniformity of the oxides grown on high-purity Sn. A strong linear relationship between the average steady-state current density and anodizing potential was also observed.

Highlights

SnO2 based materials have become of growing interest due to their promising electronic, optical, and photoelectrochemical properties and wide potential applications, for example, in solid-state gas sensors [1,2,3], solar cells [4], and catalysts [3]
It should be mentioned that a further application of nanoporous tin oxide depends on the morphology, composition, and structure of the oxide layer which are strongly affected by anodizing conditions such as applied potential, kind and concentration of electrolyte, temperature, purity and shape of the substrate, or even electrochemical cell geometry
Anodic oxidation of all Sn substrates in oxalic acid electrolyte resulted in the formation of nanoporous oxide films on the metal surface

Summary

Introduction

SnO2 based materials have become of growing interest due to their promising electronic, optical, and photoelectrochemical properties and wide potential applications, for example, in solid-state gas sensors [1,2,3], solar cells [4], and catalysts [3]. Anodically grown nanoporous tin oxides can offer many promising applications, for example, in solid-state gas sensors [15, 24, 29], lithium-ion batteries [30,31,32,33], solar cells [23], supercapacitors [34], and photonic crystals [20]. It should be mentioned that a further application of nanoporous tin oxide depends on the morphology, composition, and structure of the oxide layer which are strongly affected by anodizing conditions such as applied potential, kind and concentration of electrolyte, temperature, purity and shape of the substrate, or even electrochemical cell geometry. We discussed the effect of anodizing conditions on the formation and structure of anodic tin oxides formed during anodization of low-purity Sn foil in a conventional electrochemical cell with vertically aligned electrodes [35]. We focus mainly on the effect of different cell geometry on the growth and morphology of nanoporous tin oxide layers and on possibilities for fabricating anodic oxides on various Sn substrates

Materials and Methods

Results and Discussion

Conclusions