Enhancing <i>p-d</i> hybridization via synergistic regulation of spatial and energetic orbital overlap in Ba-doped LaNiO₃ epitaxial films for oxygen evolution activity

Abstract The hybridization between oxygen 2 p and transition-metal 3 d states largely determines the electronic structure near the Fermi level and related functionalities of transition metal oxides (TMOs). Considerable efforts have been made to manipulate the p - d hybridization in TMOs by tailoring the spatial orbital overlap via structural engineering. Here, we demonstrate an enhanced p - d hybridization in Ba 2+ -doped LaNiO 3 epitaxial films by simultaneously acting on the spatial and energetic overlaps between the O-2 p and Ni-3 d orbitals. Combining X-ray absorption spectroscopy and first-principles calculations, we reveal that the enhanced hybridization stems from the synergistic effects of a reduced charge transfer energy due to hole injection and an increased spatial orbital overlap due to straightening of Ni-O-Ni bonds. We further showcase that the enhanced p - d hybridization can be utilized to promote the oxygen evolution activity of LaNiO 3 . This work sheds new insights into the fine tuning of the electronic structures of TMOs for enhanced functionalities.