Ethanol and ethylene glycol on Ni/Pt(111) bimetallic surfaces: A DFT and HREELS study
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The reactions of ethanol and ethylene glycol have been studied on Ni/Pt(1 1 1) bimetallic surfaces using density functional theory (DFT) and high resolution electron energy loss spectroscopy (HREELS). A linear correlation has been observed between the binding energies of ethanol, ethoxy, and ethylene glycol species and the surface d-band center, with increasing binding energy as the d-band center shifts closer to the Fermi level. HREELS measurements have identified the bond scission sequence of ethanol and ethylene glycol on Ni/Pt(1 1 1) bimetallic surfaces. Two bimetallic surfaces can be formed that possess very different chemical properties: one with a monolayer of Ni atoms on top of Pt(1 1 1) designated Ni-Pt-Pt(1 1 1), and the other with the Ni atoms diffusing into the subsurface region, designated Pt-Ni-Pt(1 1 1). At 120 K ethanol adsorbs molecularly with the O-H bond intact on Pt(1 1 1) and Pt-Ni-Pt(1 1 1), while dissociative adsorption is observed on Ni-Pt-Pt(1 1 1) and Ni(1 1 1) film surfaces. Ethylene glycol adsorbs molecularly with the O-H bond intact on all four surfaces at 200 K, and desorbs reversibly from Pt(1 1 1) and Pt-Ni-Pt(1 1 1). In contrast, ethylene glycol undergoes decomposition on Ni-Pt-Pt(1 1 1) and Ni(1 1 1) film surfaces through O-H bond cleavage, forming an ethylenedioxy (-OCH2CH2O-) intermediate. This intermediate reacts by further dehydrogenation and C-C bond scission to eventually form CO. Overall, the HREELS results are consistent with TPD studies that show the reforming activities of ethanol and ethylene glycol follow the trend Ni-Pt-Pt(1 1 1) > Ni(1 1 1) film > Pt(1 1 1) > Pt-Ni-Pt(1 1 1). 2008 Elsevier B.V. All rights reserved.
