Mechanism of the autothermal reforming reaction of methane on Pt(1 1 1) surfaces: A density functional theory study

Highlights: • The preferred adsorption oxygen-containing species is formyl on the (1 1 1) surface. • Methane can be dissociated and oxidatively dehydrogenated to form carbon. • Adsorbed hydroxyl radicals are identified as insignificant. • The pathways involving hydroxyl radicals play a minor role in the overall process. • The primary reaction pathways are the oxidation of methane on the (1 1 1) surface. Density functional theory calculations were carried out to better understand the reaction mechanism for the autothermal reforming of methane on Pt(1 1 1) surfaces. Particular focus was placed upon gaining a more complete understanding of the adsorption, oxidation, combination, and dehydrogenation processes involved in the autothermal reforming reaction. The adsorption energies for various species on the (1 1 1) surface were computed, and the preferred adsorption geometry for various species was determined. The primary reaction pathways were determined based on the reaction barriers and energies for all the elementary steps involved in the processes. The results indicated that the preferred adsorption oxygen-containing species is formyl due to its lowest adsorption energy on the (1 1 1) surface. Methane can be dissociated on the (1 1 1) surface to generate methyl and then further oxidatively dehydrogenated to form carbon. The elementary reaction pathways involving hydroxyl radicals play a minor role in the overall autothermal reforming process due to the low coverage of hydroxyl radicals on the (1 1 1) surface. The reaction pathways involving hydroxyl radicals may be relevant only to the formation process of methanol fragments from carbon adsorbed on the (1 1 1) surface due to its low reaction barrier. Finally, the primary reaction pathways are the oxidation of methane on the (1 1 1) surface: CH₄ → CH_3,adsorbed → CH_2,adsorbed → CH_adsorbed → C_adsorbed → CO_adsorbed.