Specifically, in the TiO1.69 structure, the Ti atoms at the outermost layer are positioned in non-lattice sites identical to those of titanium interstitials. As a result, this layer consists entirely of vertically oriented TiO5 polyhedra with one apical oxygen vacancy along the apical axis. This arrangement exposes an excess number of coordinatively unsaturated (cus) Ti sites, which could serve as active binding sites for cluster catalysts or reactive adsorbates. Given the potential implications of these structural features on the electronic properties and their influence on catalytic activity, we will explore this aspect in more detail in the following sections.