Trend in the C=C and C=O bond hydrogenation of acrolein on Pt-M (M = Ni, Co, Cu) bimetallic surfaces

Acrolein, the smallest alpha,beta-unsaturated aldehyde, is used as a probe molecule to study the effect on the hydrogenation activity toward the C=C and C=O bonds due to the presence of a 3d transition metal either on the surface or in the subsurface region of a Pt(1 1 1) substrate. Temperature programmed desorption (TPD), high-resolution electron energy loss spectroscopy (HREELS), and density functional theory (DFT) modeling are used to help explain the trend in the overall hydrogenation activity and selectivity toward the corresponding unsaturated alcohol (2-propenol) on the 3d/Pt(1 1 1) bimetallic surfaces. The hydrogenation activity on the subsurface Pt-3d-Pt(1 1 1) structures displays the following trend: Pt-Ni-Pt(1 1 1) > Pt-Co-Pt(1 1 1) > Pt-Cu-Pt(1 1 1) based on the TPD yields. The absolute yield toward 2-propenol is also the highest on Pt-Ni-Pt(1 1 1), which is further enhanced by the presence of preadsorbed hydrogen. In contrast, the selective hydrogenation does not occur on the surface monolayer 3d-Pt(1 1 1) structures. The TPD results are consistent with HREELS measurements of different vibrational features after the adsorption and reaction of acrolein on the subsurface Pt-3d-Pt(1 1 1) and surface 3d-Pt(1 1 1) structures. In addition, DFT calculations suggest that the different hydrogenation activities between the subsurface and surface structures appear to be related to the differences in the binding energy of acrolein on the corresponding bimetallic surfaces. (c) 2009 Elsevier Inc. All rights reserved.