Enhanced Oxygen Evolution Electrocatalysis in Strained A-Site Cation Deficient LaNiO 3 Perovskite Thin Films.

As the BO ₆ octahedral structure in perovskite oxide is strongly linked with electronic behavior, it is actively studied for various fields such as metal-insulator transition, superconductivity, and so on. However, the research about the relationship between water-splitting activity and BO ₆ structure is largely lacking. Here, we report the oxygen evolution reaction (OER) of LaNiO ₃ (LNO) by changing the NiO ₆ structure using compositional change and strain. The 5 atom % La deficiency in LNO resulted in an increase of the Ni-O-Ni bond angle and an expansion of bandwidth, enhancing the charge transfer ability. In-plane compressive strain derives the higher d _{z ²} orbital occupancy, leading to suitable metal-oxygen bond strength for OER. Because of the synergistic effect of A-site deficiency and compressive strain, the overpotential (η) of compressively strained L _0.95 NO film is reduced to 130 mV at j = 30 μA/cm ² compared with nonstrained LNO (η = 280 mV), indicating a significant enhancement in OER.