In situ investigations of reactions over well-defined model catalysts are essential to gain amolecular level understanding of catalytic processors. Inverse model catalysts (oxide-nanoparticles/metal-substrate configuration) show remarkable activity for many catalytic reactions such as water-gas shift, methanol synthesis, and CO oxidation. We have prepared and characterized an inverse CeOx-CuyO/Cu(111) model catalyst, and studied the water-gas shift reaction (WGSR; CO+H2O ? H2+CO2) using near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS), infrared reflection absorption spectroscopy (IRRAS) and density functional theory (DFT) calculations.1 The most abundant surface species on Cu(111) under WGSR conditions is adsorbed CO whereas adsorbed bent carboxylate (CO2d-) species are identified over CeOx/Cu(111) with the ceria in a highly reduced state. By combining in situ experimental results with calculations, we show that the precursor for the formation of CO2d- is a carboxy (HOCO) intermediate on the metal-oxide interface. Even though the WGSR over CeOx/Cu(111) catalysts can occur by both redox and associative mechanisms, the study presented here shows that the presence of the oxide-metal interface activates the more efficient associative mechanism pathway and leads to an increase by more than one order of magnitude in the activity of the CeOx/Cu(111) system relative to that of Cu(111). The observed results also indicate that formate species are not likely to be key intermediates in the WGSR over CeOx/Cu(111). Our study illustrates the power of in situ mechanistic studies on well-defined catalysts and the important role that metal-oxide interfaces can play in catalysis.(1) Mudiyanselage, K.; Senanayake, S. D.; Feria, L.; Kundu, S.; Baber, A. E.; Graciani, J.; Vidal, A. B.; Agnoli, S.; Evans, J.; Chang, R.; Axnanda, S.; Liu, Z.; Sanz, J. F.; Liu, P.; Rodriguez, J. A.; Stacchiola, D. J. Angew. Chem. Int. Ed. 2013  , 52, 1.

Importance of the metal�oxide interface in catalysis: In situ studies of the water�gas shift reaction by ambient-pressure X-ray photoelectron spectroscopy

246th National Meeting (2013)

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