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First-Principles Study of Water Dissociation on PdZn near Surface Alloys

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journal contribution
posted on 29.09.2011, 00:00 by Yucheng Huang, Zhao-Xu Chen
Recently, it was proposed that the different behavior of water on PdZn multilayer and monolayer is responsible for the different selectivity toward CO2 in methanol steam reforming process on the Zn deposited Pd surface annealed at different temperatures. [Angew. Chem. 2010, 49 (18), 3224–3227.] To explore this interesting and important phenomenon, we investigate water adsorption and dissociation in various aggregation forms on PdZn multi- and monolayer model surface alloys of both flat and stepped surfaces, using density functional theory and slab models. Our calculations show that the water is more stable on the multilayer. Surface defects and aggregation favor H2O dissociation. Contrary to the point of view that PdZn monolayer cannot activate H2O whereas multilayer can, our first-principles results clearly demonstrate that the multilayer is less active for water dissociation than the monolayer. This discrepancy calls for further studies on this system both experimentally and theoretically.