The Role of Gold-Alumina Template in the Electrochemical Deposition of CeO2 Nanotubes

Abstract

Electrochemical synthesis employing porous membranes previously metalized with a gold layer as a template is an easy and widespread method to obtain 1D nanostructures. Nevertheless, experimental factors for tuning the morphology and structural details of such nanostructures are still investigated. The influence of the amount of gold on morphology and structure of the 1D systems is studied for the first time. For this purpose, CeO2 nanotubes are synthesized via template-based lectrodeposition inside the pores of gold-sputtered anodic aluminum oxide (AAO). X-ray diffraction and electron microscopy techniques, including 3D electron tomography, are applied for the characterization of the template and the nanostructures. On one hand, the results reveal how gold is deposited on top and inside the pores of the AAO as a thin layer or as particles. On the other hand, the 1D systems consist of nanotubes formed by randomly oriented fluorite-like nanocrystals (2–5 nm), which features a network of inner walls whose compactness directly relates to the thickness of the gold-sputtered layer. From the combined analysis of voltage–time curves recorded during electrodeposition and the 2D, 3D structural information, a growth mechanism is proposed, which may enlighten paths to tailor the morphology and properties of CeO2 1D nanostructures