Oxide nanoparticles, like TiO₂ nanoparticles, are often applied in electrodes and photocatalytic systems. The morphology and shape of these nanoparticles can be easily tuned with experimental conditions, which raises the question of how much the electro- and photochemical properties are affected by the nanoparticle geometry. We showed examples when the morphology of anatase-type TiO₂ electrodes was had a significant influence on the efficiency and selectivity of the electrochemical process. [1] The goal of our computational studies is to understand better how charge carriers behave in these oxide nanoparticles and how the shape of the particle influences this behavior. 

We studied the electronic states around the bandgap in anatase-type TiO₂ nanoparticles of different shapes with (101) and (001) facets using Density Functional based Tight Binding (DFTB) and DFT methods. The previous calculation has already shown that most orbitals of the valence and conduction bands form delocalized band-like orbitals; however, there are a significant number of localized states at the lower edge of the conduction band, too. The calculations clearly show the position of these trapping sites when we compare the electron density of neutral and charged nanoparticles.

Reference:

[1] Selectivity enhancement in the electrochemical reduction of oxalic acid over titanium dioxide nanoparticles achieved by shape and energy-state control. H Eguchi, K Kato, G Juhasz, M Yamauchi - Catalysis Science & Technology, 2021