Synergistic Role of Eg Filling and Anion–Cation Hybridization in Enhancing the Oxygen Evolution Reaction Activity in Nickelates

Transition-metal perovskite oxides (ABO3) have been demonstrated to exhibit the excellent catalytic activity of the oxygen evolution reaction (OER). Here, we show that the layered perovskite Ruddlesden–Popper (RP) series An+1BnO3n+1 is an ideal material system with high tunability of the electronic structure and orbital occupancy, providing a clean system to reveal the important factors in optimizing the OER activity in transition-metal oxides. We show that the catalysis performance is significantly enhanced in the layered nickelate (Lan+1NinO3n+1) compounds with n ≥ 3 and peaked at the n = 5 member, which is about 4 times higher than that in the corresponding perovskite compound (LaNiO3). Our work suggests that the variation of the n value can effectively modulate the NiO2 electronic properties, and the proper combination of Op-Nid hybridization and eg occupancy can result in substantially enhanced catalytic performance in transition-metal oxides.