Understanding the Enhancement Mechanism of A-Site-Deficient La_<i>x</i>NiO₃ as an Oxygen Redox Catalyst

Abstract

Lanthanide perovskite oxides have attracted much attention as an oxygen reduction and evolution catalyst because of their high chemical stability and composition adjustability. A defect strategy has been applied to enhance their electrocatalytic activity with the modulation of the crystal/electronic structure. However, the intrinsic roles of the defects, particularly A-site vacancies, are poorly understood. Herein, we prepare LaxNiO3 with various ratios of A-site vacancies by a facile nonstoichiometric strategy, which has boosted the dual-function catalytic activity of LaNiO3. More importantly, the enhancement mechanism of A-site-deficient LaxNiO3 as an oxygen redox catalyst has been unveiled. Induced vacancy defects on the A sites raise a compression strain in the NiO6 octahedron, exerting a positive enhancement on Ni–O covalency. Furthermore, the eg electron filling in the active cation Ni and the overlapping state of Ni 3d–O 2p hybridization have also been optimized, in which renovation will further boost the catalytic ability of oxygen redox processes. This work not only clarifies the intrinsic roles of A-site deficiency in the structure and electrocatalytic activities of perovskite oxides but also presents some insights into the design and exploration of high-activity catalysts by cation defect modulation.