Elucidating dz2 orbital selective catalytic activity in brownmillerite Ca2Mn2O5

• Main Authors: Yue Lu, Feng Lu, Zhi Yang, Jie Wu, Hongyun Yu, Xinjian Xie, Jianping Xu, Fangyi Cheng, Jun Chen, Ka Xiong, Hui Liu, Wei-Hua Wang, Jianzhou Zhao, Weichao Wang
• Format: Article
• Language: English
• Published: AIP Publishing LLC 2016-09-01
• Series: AIP Advances
• Online Access: http://dx.doi.org/10.1063/1.4963079

3d-orbital filling in transition metal oxide is crucial to govern the catalytic activity in oxygen evolution reduction, nevertheless, it is not fundamentally accessible why specific orbital occupation produces a highest catalytic performance. Here, we utilize brownmillerite Ca2Mn2O5 to clarify the orbital selective catalytic behavior due to the crystal field splitting and on-site coulomb interactions. Within density functional theory plus dynamical mean field theory, Ca2Mn2O5 shows a paramagnetic Mott insulating behavior at room temperature, consistent with optical adsorption spectra and magnetic susceptibility. As the center of the dz2 orbital locates in the lower Hubbard sub-band, the unit occupation on dz2 orbital provides a moderate bonding with external O* species to cause a high catalytic activity of Ca2Mn2O5 with a square pyramid crystal field. Such concept of unit occupation of dz2 near Fermi level could be extended to other crystal fields for future design of oxide catalysts.