The acid–base and redox reactivity of CeO2 nanoparticles: Influence of the Hubbard U term in DFT + U studies

Abstract The interaction of small molecules with acid–base and redox centers in small Ce 21 O 42 nanoparticles has been theoretically investigated using the DFT + U approach with the PW91 functional and U = 0.2 and 4 eV, in order to determine the influence of the U value on the trends observed in selected properties describing such interactions. CO adsorption at low coordinated Ce 4 + Lewis acid centers, water adsorption and dissociation at acid–base pairs, formation of oxygen vacancy defects by removal of an oxygen atom from the system, and interaction of molecular O 2 with such defects have been considered. The largest effect of the value of U is found for the description of the reduced Ce 21 O 41 nanoparticle. In all other cases involving stoichiometric and oxidized Ce 21 O 42 and Ce 21 O 43 systems, the trends in the calculated adsorption and reaction energies, optimized geometries, charge distribution, and vibrational frequencies are quite similar at the three levels considered.