(630d) Insights into the Most Ideal Surface Chemistry for CH4 Dry Reforming from Oxide-Supported Intermetallic Compound Nanoparticles of Well-Defined Bulk and Surface Composition

Methane reforming or partial oxidation reactions require unique surface chemistry towards C, O, and H that may not be presented in entirety by monometallic transition metal (TM) or TM+TM alloy catalysts. When utilizing CO₂ to upgrade CH₄, one must activate two recalcitrant bonds while still achieving carbon oxidation at the catalyst surface. Since most late TMs present moderately similar surface chemistry towards C, O, and H, it is necessary to modify their electronic structure significantly to enhance reactivity towards O and H and lessen reactivity towards C. These modifications and wholly new surface chemistry may be achieved through the use of compositionally ordered mixtures of TMs and larger p-block elements, coined intermetallic compounds (IMCs). The IMC catalysts not only exhibit excellent activity in CH₄ dry reforming and tunable H₂:CO product ratios, their innate stability dramatically limits catalyst composition changes as well as coke-driven deactivation. Results suggest that elevated surface reactivity towards O and H leads to a more balanced surface-bound intermediate mixture that can limit coke formation and enhance rates. Both computational surface science results and experimental synthesis and performance tests will be discussed. Oxide-supported IMC nanoparticles with well-defined bulk and surface compositions allowed connections between catalyst performance and surface properties to be determined experimentally. DFT and CO DRIFTS studies further supported the proposal that elevated reactivity towards O and H and lower reactivity towards C are beneficial in the reaction.