Atomic Reconstruction\nand Oxygen Evolution Reaction\nof Mn₃O₄ Nanoparticles

Abstract

Understanding the chemical states of individual surface\natoms and\ntheir arrangements is essential for addressing several current issues\nsuch as catalysis, energy stroage/conversion, and environmental protection.\nHere, we exploit a profile imaging technique to understand the correlation\nbetween surface atomic structures and the oxygen evolution reaction\n(OER) in Mn₃O₄ nanoparticles. We image surface\nstructures of Mn₃O₄ nanoparticles and observe\nsurface reconstructions in the (110) and (101) planes. Mn³⁺ ions at the surface, which are commonly considered as the active\nsites in OER, disappear from the reconstructed planes, whereas Mn³⁺ ions are still exposed at the edges of nanoparticles. Our\nobservations suggest that surface reconstructions can deactivate low-index\nsurfaces of Mn oxides in OER. These structural and chemical observations\nare further validated by density functional theory calculations. This\nwork shows why atomic-scale characterization of surface structures\nis crucial for a molecular-level understanding of a chemical reaction\nin oxide nanoparticles.