Enhanced Electrocatalytic Oxygen Evolution Activity by Tuning Both the Oxygen Vacancy and Orbital Occupancy of B‐Site Metal Cation in NdNiO3

Perovskite oxides have been explored as promising electrocatalysts for the oxygen evolution reaction (OER), while a lack of understanding of key factors impacting the catalytic activity restricts their further design and development. Here, for the first time, the contributions of oxygen vacancy (VO) and orbital occupancy of B‐site cations to the catalytic activity of NdNiO3 films are systematically investigated. It is found that OER activity follows a typical volcano‐shaped dependence on the oxygen pressure. In the range of 0.2–10 Pa, proper concentration of VO can provide a moderate bonding strength with intermediate hydroxyl OH* and the increased ratio of Ni3+/Ni2+ provides a more favorable occupancy of eg orbital for the catalytic activity; while in the range of 10–60 Pa, insufficient concentration of VO leads to an enhanced strength of hybridization between Ni 3d and O 2p band and thus deteriorated catalytic activity. The superior OER catalytic performance can be only achieved with both appropriate concentration of VO and the ratio of B‐site metal cations with different valences. The oxygen evolution reaction (OER) activity of NNO films exhibit a volcano‐shaped dependence on oxygen pressure, and the excellent catalytic performance is achieved with both the appropriate concentration of oxygen vacancy and the ratio of Ni3+/Ni2+. The optimized NdNiO3 films are shown to have the best electrocatalytic performance toward the OER among the nickelate‐based films.