Controlling the Cation Exsolution of Perovskite to Customize Heterostructure Active Site for Oxygen Evolution Reaction.

Perovskite oxides are an important class of oxygen evolution reaction (OER) catalysts offering an ordered atomic arrangement and a highly flexible electronic structure. Currently, understanding and adjusting the dynamic reconstruction of perovskite during the OER process remains a formidable challenge. Here, we report the artificial construction of a heterostructure by the cation exsolution of perovskite to control the active site formation and reconstruction. The deliberately made La deficiency in LaNiO 3 perovskite facilitates the original segregation of NiO from the parent matrix and forms a well-defined interface between perovskite parent and NiO exsolution phase. The dynamic formation process of such heterojunction was studied by density functional theory computation and high quality imaging characterization. Due to the valence redistribution of Ni ions caused by the interfacial electron transfer, the in situ formed LaNiO 3 /NiO heterostructure displays high electroactivity. Therefore, the LaNiO 3 /NiO heterostructure exhibits a dynamic surface evolution feature with the generation of the highly active NiOOH layer under a low anodic potential (∼1.35 V vs RHE) during the OER process, which is very different from the conventional LaNiO 3 with a stoichiometry and NiO catalysts. With the newly formed heterostructure, the reconstructed catalysts impart a 4.5-fold increase in OER activity and a 3-fold improvement in stability against La and Ni dissolution during the OER process. This work provides a feasible interface engineering strategy for artificially controlling the reconstruction of the active phase in high-performance perovskite-based electrocatalytic materials.