First-principles investigation on redox properties ofM-dopedCeO2(M=Mn,Pr,Sn,Zr)

The effects of $M$ $(M=\text{Mn},\text{Pr},\text{Sn},\text{Zr})$ doping on the redox thermodynamics of ${\text{CeO}}_{2}$ 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 ${\text{CeO}}_{2}$ have been clarified. Compared with the case of pure ${\text{CeO}}_{2}$, the decrease in the O-vacancy formation energy for the Zr-doped ${\text{CeO}}_{2}$ is mostly caused by the structural distortion, whereas the decrease for Mn-, Pr-, or Sn-doped ${\text{CeO}}_{2}$ 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.