In Situ Modulation of A-Site Vacancies in LaMnO Perovskite for Surface Lattice Oxygen Activation and Boosted Redox Reactions.

Modulation of A-site defects is crucial to the redox reactions on ABO perovskites for both clean air application and electrochemical energy storage. Herein we report a scalable one-pot strategy for in situ regulation of La vacancies (V ) in LaMnO by simply introducing urea in the traditional citrate process, and further reveal the fundamental relationship between V creation and surface lattice oxygen (O ) activation. The underlying mechanism is shortened Mn-O bonds, decreased orbital ordering, promoted MnO bending vibration and weakened Jahn-Teller distortion, ultimately realizing enhanced Mn-3d and O-2p orbital hybridization. The LaMnO with optimized V exhibits order of magnitude increase in toluene oxidation and ca. 0.05 V versus RHE (reversible hydrogen electrode) increase of half-wave potential in oxygen reduction reaction (ORR). The reported strategy can benefit the development of novel defect-meditated perovskites in both heterocatalysis and electrocatalysis.