Electrochemical growth and characterization of micro/nanostructured SnOx with crater-like morphology

Abstract

A comprehensive study concerning the mechanism of electrochemical growth of hierarchical SnOx nanostructures via electrochemical oxidation of metallic tin is presented. Materials were synthesized by simple one-step anodization carried out in a strongly alkaline electrolyte (1 M NaOH) under a potentiostatic regime (11 V) for various durations (2.5–30 min). Morphological features of the obtained materials were carefully investigated by FE-SEM. It was proven that upon prolonging anodization time, the initially formed compact oxide layer is gradually converted into the characteristic crater-like structures. Such hierarchically aligned materials are comprised of the compact middle part being the remnants of the passive film and highly porous slopes with a typical, highly-cracked morphology with channels having diameters of between 90 and 100 nm. The chemical composition of obtained materials was examined using X-ray powder diffraction (XRPD), and Raman spectroscopy confirming that after thermal treatment in air at 200 °C SnO, together with Sn3O4 forms are present within the highly-defective SnOx matrix. The photocatalytic performance of the annealed samples was also verified by monitoring the rate of decolorization of methylene blue (MB) under simulated sunlight. The achieved degradation efficiency of ∼84% after 180 min of irradiation confirmed the broad potential of such kind of anodic tin oxide layers in photocatalytic applications.