First-principles investigation on redox properties of M-doped CeO2 (M=Mn,Pr,Sn,Zr)

The effects of M (M=Mn,Pr,Sn,Zr) doping on the redox thermodynamics of CeO2 have been investigated using first-principles density-functional theory calculations with the on-site Coulomb interaction taken into account. Two different mechanisms for the O-vacancy formation in doped CeO2 have been clarified. Compared with the case of pure CeO2, the decrease in the O-vacancy formation energy for the Zr-doped CeO2 is mostly caused by the structural distortion, whereas the decrease for Mn-, Pr-, or Sn-doped CeO2 originates from the electronic modification as well as from the structural distortion. It is found that the electronic modification occurs in those dopants whose uttermost atomic orbitals are half or fully occupied by the filling of the excess electrons left by the formation of the O vacancy. Two effects also contribute to concentration dependence of the O-vacancy formation energies for different dopant species.