Theoretical Investigation on H2 Oxidation Mechanisms over Pristine and Sm-doped CeO2(111) Surfaces

Abstract Samarium-doped transition metal oxides are recognized as promising anode materials for solid oxide fuel cell (SOFC). The adsorption and oxidation of hydrogen on both pristine and Sm-doped CeO2(111) are studied using Hubbard-U density functional theory (DFT+U). Our calculations suggest that a H atom could bind to the doped Sm atom through a secondary bonding, weaker than covalent bonding but stronger than Van der Waals force. This special H−Sm interaction facilitates H2 dissociation (and H2O formation) step by dramatically reducing the energy barrier from 1.092 (3.540) eV to 0.532 (0.158) eV when compared with pristine CeO2(111), indicating that Sm doping could significantly improve the catalytic activity of CeO2 for H2 oxidation. Microkinetic modeling further confirms the crucial role played by doped Sm, and the Sm-mediated pathway is dominant at medium and low temperature (300 ∼ 800 K), contributing to good low-temperature performance of CeO2-based anode in SOFC.