Berlin 2018 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 9: Focus Session: Frontiers in Reducible Oxide Surface Science I

O 9.3: Hauptvortrag

Montag, 12. März 2018, 11:30–12:00, HFT-FT 131

Unraveling surface chemistry Of C-H reforming reactions over Ni-CeOx(111) catalysts — •Sanjaya Senanayake — Brookhaven National Laboratory, Upton, NY 11973, USA

We have utilized a combination of model and powder catalysts composed of Ni and CeOx, employing in situ spectroscopies to elucidate the active state and mechanistic steps associated with C-H bond activation in the ethanol steam reforming (ESR) and Methane Dry Reforming (DRM) reactions. Our results reveal that surface layers of the catalyst substrate can be probed under dynamic reaction conditions using AP-XPS, revealing the surface as highly reduced and hydroxylated under reaction conditions while the small supported Ni nanoparticles are present as Ni0/NixC essential for the C-H conversion processes. In addition, in both reactions, a multifunctional, synergistic role is highlighted in which Ni, CeOx and the interface provide an ensemble effect in the active chemistry that activates C-H (Ethanol/Methane) and leads to H2. We correlate changes to the active phases leading to both C-C and C-H bond cleavage in ESR, and C-H and C-O in DRM but also for carbon accumulation or coking that are intrinsic properties of such reactions. The interface (Ni-ceria) facilitates the C-C bond breaking step while the pathways that lead to H2 production may occur from the recombination of OH and CHx species. Additionally, we discuss important insights into the stability and selectivity of the catalyst in the presence of co-reactants and the strategies that will help correlate improved catalyst design for selective bond breaking and forming processes.