Single-Atom Pd Catalyst on a CeO₂ (111) Surface for Methane Oxidation: Activation Barriers and Reaction Pathways

Employing density functional theory, we delved into the comprehensive pathways for methane oxidation on the Pd single atom supported with CeO2(111) encompassing sequential methane dehydrogenation, O2 dissociation, and oxidation processes. The introduction of a Pd atom into CeO2(111) led to a reduction in the barrier for CH4 dissociation to 0.50 eV. The methane dehydrogenation proceeded through a series of reactions: CH4 → CH3 → CH2 → CH → C, with all dehydrogenation steps being exothermic except the CH3 → CH2 step. The O2 dissociation reaction (O2 → O* + O*) is thermodynamically exothermic, with a dissociation barrier of 2.12 eV over Pd@CeO2. Subsequently, the generation of CO2 via the C* + O* and CO* + O* reactions is characterized by thermodynamically exothermic processes, with reaction energies of −1.20 and −1.01 eV, respectively. On the other hand, water production occurs through O* + H (an exothermic reaction) and OH* + H (an endothermic reaction) with reaction energies of −0.80 and +0.64 eV, respectively. These findings offer valuable insights into the potential pathways for single-atom catalysis involving transition metals supported on CeO2(111) in methane oxidation for industrial application.