Effect of Pt Deposits on TiO2 Electrocatalytic Activity Highlighted by Electron Tomography.

Characterizing materials at small scales presents major challenges in the engineering of nanocomposite materials having a high specific surface area. Here, we show the application of electron tomography to describe the three-dimensional structure of highly ordered TiO2 nanotube arrays modified with Pt nanoparticles. The titanium oxide nanotubes were prepared by the electrochemical anodization of a Ti substrate after which Pt was deposited by magnetron sputtering. Such a composite shows high electrochemical activity that depends on the amount of the metal and the morphological parameters of the microstructure. However, a TiO2 structure modified with metallic nanoparticles has never been visualized in 3D, making it very difficult to understand the relationship between electrocatalytic activity and morphology. In this paper, TiO2 nanotubes of different sizes and different amounts of Pt were analyzed using the electron microscopy technique. Electrocatalytic activity was studied using the cyclic voltammetry (CV) method. For selected samples, electron tomography 3D structure reconstruction was performed to describe their fine microstructure. The highest activity was detected in the sample having bigger nanotubes (25 V) where the porosity of the structure was high and the Pt content was 0.1 mg cm-2. 3D imaging using electron tomography opens up new possibilities in the design of electrocatalytic materials.