Atomic Layer Deposition Grown Titania Phases (TiO₂, TiO, Ti₂O) and its Influence on Water Splitting Electrocatalysis

Abstract The systematic engineering of atoms and the precise tuning of their arrangement can unlock a range of hidden yet remarkable properties of materials. In this study, different phases of titanium oxide, including TiO₂, TiO, and Ti₂O, are developed using the Atomic Layer Deposition (ALD) technique. Notably, a novel Ti₂O electride with a pbcn space group is identified, and variations in stoichiometries, such as Ti_1.80O, Ti_2.05O, and Ti_2.30O, are observed through Rietveld analysis of the corresponding X‐ray Diffraction (XRD) data. High‐resolution transmission electron microscopy (HRTEM) imaging further revealed line defects such as stacking faults and edge dislocations in Ti₂O. The interplay of stoichiometric defects in Ti₂O electrides leads to tunable electrocatalytic behavior, enabling transitions from oxygen evolution to hydrogen evolution reactions. Importantly, using Density functional theory (DFT), Paterson analysis, and Fourier electron density mapping, the exceptional metallic properties of Ti₂O are rationalized as arising from its unique spatial electron density distribution. Overall, this work underscores the significance of atomic‐level structure engineering and opens the door to a new class of titanium oxide catalysts for electrochemical water splitting.