Controlling Selectivity and Stability in the Hydrocarbon Wet-Reforming Reaction Using Well-Defined Ni plus Ga Intermetallic Compound Catalysts

In this study, we present the use of compositionally and structurally well-defined, oxide-supported nanoparticle Ni + Ga intermetallic compound (IMC) catalysts in the wet reforming of propane. The definition of the IMC catalysts allowed for more direct connections to be made between catalyst bulk and surface compositions and catalyst performance in wet reforming. We show that Ni + Ga catalysts exhibit comparable or better rates of reaction on a per-site basis and improved stability in comparison to other leading formulations. We also demonstrate excellent control over product selectivity as a function of Ni + Ga IMC bulk and surface compositions with nearly ideal selectivity toward CO2/H-2 or CO/H-2 achieved. Selectivity toward the production of smaller hydrocarbons could also be suppressed significantly due to uniquely limited rehydrogenation kinetics of the Ni + Ga IMCs. Our studies also shed light on the stability of Ni + Ga IMCs under reaction conditions and how high conversion in reactions that involve many strongly bound reaction intermediates can lead to IMC phase relaxation to the most stable phase with concomitant surface composition and catalytic performance changes. Correlations between surface chemistry and catalyst performance were afforded by both the well-defined nature of the IMCs and computational surface science studies.