Photoinduced selective electrons transfer and secondary orbital splitting in CeO2 bulk

Abstract

As a typical wide bandgap semiconductor and a ubiquitous constituent in catalytic systems for a variety of applications, the dynamical processes of photoinduced electrons transfer (PET) in CeO2 are crucial for advancing the understanding of semiconductor physics and photocatalysis. In this study, we analyze orbital-resolved PET in CeO2 using real-time time-dependent density functional theory simulations. We discovered remarkable selectivity in the interatomic PET in CeO2. In particular, the photogenerated electrons maintain a consistent transport pathway from the O-2p orbital to the Ce-4f and Ce-5d orbitals, irrespective of the polarization state (linear and circular) of the external optical field. We further observed a secondary splitting found upon the crystal field splitting in Ce-5d and Ce-4f orbitals due to the symmetry breaking of the original coordination field of Ce atom. The secondary splitting is manipulated by the polarization state of the external optical field and the detailed dependency is deciphered, which provides us guidance for manipulating the orbital splitting by optical. Comparative analysis with the electrons transfer characteristics induced by hole doping reveals that the selectivity of interatomic electron transfer and the secondary splitting are unique to the photoexcitation process. Our results and findings shed new light on the microscopic mechanisms and dynamical processes underlying PET in CeO2 and may be generalized to other oxide semiconductors. These new insights may be beneficial for deciphering the ultrafast time-resolved spectroscopy experiments and for understanding the photocatalysis mechanisms in ceria-based photocatalysis materials.