Enhanced Electrocatalytic Oxygen Evolution Activity by Tuning Both the Oxygen Vacancy and Orbital Occupancy of B‐Site Metal Cation in NdNiO 3

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 (V O ) and orbital occupancy of B‐site cations to the catalytic activity of NdNiO 3 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 V O can provide a moderate bonding strength with intermediate hydroxyl OH* and the increased ratio of Ni 3+ /Ni 2+ provides a more favorable occupancy of e g orbital for the catalytic activity; while in the range of 10–60 Pa, insufficient concentration of V O 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 V O and the ratio of B‐site metal cations with different valences.