Tuning the Electronic Structure of LaNiO₃ through Alloying with Strontium to Enhance Oxygen Evolution Activity

The perovskite oxide LaNiO₃ is a promising oxygen electrocatalyst for renewable energy storage and conversion technologies. Here, it is shown that strontium substitution for lanthanum in coherently strained, epitaxial LaNiO₃ films (La_1- Sr NiO₃) significantly enhances the oxygen evolution reaction (OER) activity, resulting in performance at x = 0.5 comparable to the state-of-the-art catalyst Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3- . By combining X-ray photoemission and X-ray absorption spectroscopies with density functional theory, it is shown that an upward energy shift of the O 2p band relative to the Fermi level occurs with increasing x in La_1- Sr NiO₃. This alloying step strengthens Ni 3d-O 2p hybridization and decreases the charge transfer energy, which in turn accounts for the enhanced OER activity.