Photoinduced Femtosecond Charge Redistribution in LaNiO ₃

High Resolution Image Download MS PowerPoint Slide Perovskite oxides are at the heart of potential next-generation sustainable energy technologies, with their electronic structure and performance governed by the subtle balance between metal–oxygen covalency and ionic character. Here, we employ femtosecond X-ray absorption spectroscopy (fs-XAS) to probe the ultrafast electronic response of lanthanum nickel oxide (LaNiO 3 ), a correlated metallic perovskite and promising electrocatalyst. Upon 400 nm photoexcitation, we observe a pronounced redshift of the nickel–oxygen antibonding states, with a larger magnitude at the oxygen 1 s (−0.7 eV) than at the nickel 2 p 3/2 edge (−0.4 eV). This disparity unravels different core-hole screening, enabling us to disentangle intrinsic band shifts from final-state effects. The results establish that photoexcitation drives a transient reduction in nickel–oxygen covalency, accompanied by ligand-hole formation and a renormalization of the nickel 3 d –oxygen 2 p bands by 0.15 eV. Our findings demonstrate that even metallic nickelates undergo substantial band-structure reshaping under ultrafast excitation, providing design principles for oxide-based energy conversion materials.