  In this work, we employ first-principles simulations to investigate the spin
polarization of CeO$_2$-(111) surface and its impact on interactions between a
ceria support and Pt nanoparticles. For the first time, we report that the
CeO$_2$-(111) surface exhibits a robust surface spin polarization due to the
internal charge transfer between atomic Ce and O layers. In turn, it can lower
the surface oxygen vacancy formation energy and enhance the oxide reducibility.
We show that the inclusion of spin polarization can therefore significantly
reduce the major activation barrier in the proposed reaction pathway of CO
oxidation on ceria-supported Pt nanoparticles. For metal-support interactions,
surface spin polarization enhances the bonding between Pt nanoparticle and
ceria surface oxygen, while CO adsorption on Pt nanoparticles weakens the
interfacial interaction regardless of spin polarization.
