Issue 45, 2017

Mechanistic insights on ethanol dehydrogenation on Pd–Au model catalysts: a combined experimental and DFT study

Abstract

In this study, we have combined ultra-high vacuum (UHV) experiments and density functional theory (DFT) calculations to investigate ethanol (EtOH) dehydrogenation on Pd–Au model catalysts. Using EtOH reactive molecular beam scattering (RMBS), EtOH temperature-programmed desorption (TPD), and DFT calculations, we show how different Pd ensemble sizes on Au(111) can affect the mechanism for EtOH dehydrogenation and H2 production. The Au(111) surface with an initial coverage of 2 monolayers of Pd (2 ML Pd–Au) had the highest H2 yield. However, the 1 ML Pd–Au catalyst showed the highest selectivity and stability, yielding appreciable amounts of only H2 and acetaldehyde. Arrhenius plots of H2 production confirm that the mechanisms for EtOH dehydrogenation differed between 1 and 2 ML Pd–Au, supporting the perceived difference in selectivity between the two surfaces. DFT calculations support this difference in mechanism, showing a dependence of the initial dehydrogenation selectivity of EtOH on the size of Pd ensemble. DFT binding energies and EtOH TPD confirm that EtOH has increasing surface affinity with increasing Pd ensemble size and Pd coverage, indicating that surfaces with more Pd are more likely to induce an EtOH reaction instead of desorb. Our theoretical results show that the synergistic influence of atomic ensemble and electronic effects on Pd/Au(111) can lead to different H2 association energies and EtOH dehydrogenation capacities at different Pd ensembles. These results provide mechanistic insights into ethanol's dehydrogenation interactions with different sites on the Pd–Au surface and can potentially aid in bimetallic catalyst design for applications such as fuel cells.

Graphical abstract: Mechanistic insights on ethanol dehydrogenation on Pd–Au model catalysts: a combined experimental and DFT study

Supplementary files

Article information

Article type
Paper
Submitted
27 Jul 2017
Accepted
02 Nov 2017
First published
02 Nov 2017

Phys. Chem. Chem. Phys., 2017,19, 30578-30589

Mechanistic insights on ethanol dehydrogenation on Pd–Au model catalysts: a combined experimental and DFT study

E. J. Evans, H. Li, W. Yu, G. M. Mullen, G. Henkelman and C. B. Mullins, Phys. Chem. Chem. Phys., 2017, 19, 30578 DOI: 10.1039/C7CP05097F

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