Catalytic propane reforming mechanism over Mn-Doped CeO₂ (111)

MnO_x/CeO_x mixed oxide systems exhibit encouraging hydrocarbon oxidation activity, without the inclusion of a noble metal. Using density functional theory (DFT) methods, we examined the oxidative reforming path of propane over the Mn-doped CeO₂ (1 1 1) surface. A plausible set of elementary reaction steps are identified for conversion of propane to CO/CO₂ and H₂/H₂O over the oxide surface. The rate-limiting reaction process may vary with redox conditions, with C-H dissociation limiting under more oxidizing conditions and more complex reaction sequences, including surface re-oxidation, limiting under highly reducing conditions. The possibility of intermediate desorption from the surface during the reforming process is low, with desorption energies of the intermediates being much less favorable than further surface reactions until CO/CO₂ products are formed. The reforming paths over Mn-doped ceria are similar to those previously identified over Zr-doped ceria. The extent of surface reduction and the electronic structure of the surface intermediates are examined.