Electronic properties and native point defects of high efficient NO oxidation catalysts SmMn2O5

Mn-based oxide SmMn2O5 exhibits greatcatalytic performance in NOoxidation [Wanget al., Science337, 832 (2012)]. Nevertheless, the fundamental understanding of SmMn2O5 properties is so far not fully accessible. Here, the SmMn2O5nanoparticles are synthesized through hydrothermal methods, and the pure phase of triclinic SmMn2O5 is characterized by high-resolution tunneling electron microscope andX-ray diffraction. Furthermore, the X-ray photoelectron spectroscopy,absorption,photoluminescencespectra(PL), anddensity functional theory based first-principles calculations are employed to explore the fundamental electronic structures of pristine and defective SmMn2O5. Combined with band structure calculations, lightabsorption, andPLspectra, we first show that SmMn2O5 presents an insulating behavior with an indirectband gap of ∼1.0 eV. Between the two types of crystal fields, i.e., octahedral and tetrahedral, the later one contributes to thedz2 of the valence band edge, resulting in superiorcatalytic performance of NOoxidation. Furthermore, the native point defects in SmMn2O5 are first reported. Among the various native point defects, we demonstrate that oxygenvacancy (VO) shows the lowest formation energy in oxygen poor conditions, while the oxygen interstitial (Oi) and Mnvacancies are energetically favorable in oxygen rich situations. In other words, SmMn2O5 could be potentially utilized as an oxygen storage material.

Source: Applied Physics Letters - November 23, 2016 Category: Physics Authors: Hao-Bo Li, Zhi Yang, Jieyu Liu, Xiaolong Yao, Ka Xiong, Hui Liu, Wei-Hua Wang, Feng Lu and Weichao Wang Source Type: research