The reactive sites in faceted anatase nanoparticles

Abstract

Considering both (001) and (101) surfaces, we construct two models of anatase nanoparticles with size ranging between 182 and 774 atoms. We choose nanoparticles where the majority surface (101) decreases in surface percentage as the size of the nanoparticle increases; the minority surface (001) decreases correspondingly. Upon optimization, significant structural changes occur in the edged Ti atoms which are junctures between the (001) and (101) facets; original four-coordinated Ti atoms become three coordinated upon optimization. Analyzing the electronic properties, we observe frontier orbitals occurring as small peaks in the band gap region approximately 1 eV lower than the conduction band. We find that these mid-gap peak states are highly localized at the edged Ti atoms. Therefore, we propose that these edged Ti atoms are a key to understanding the reactivity properties exhibited in anatase nanoparticles.