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, O-2 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 O-2 dissociation reaction (O-2 -> 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.