Ethanoldecomposition on a Pd(110) surface: a density functional theory investigation

Abstract

Ethanol decomposition on Pd(110) is comprehensively investigated using self-consistent periodic density functional theory. Geometries and energies for all the intermediates involved are analyzed, and the decomposition network is mapped out to illustrate the reaction mechanism. On Pd(110), the most stable adsorption of the involved species tends to follow the gas-phase bond order rules, wherein C is tetravalent and O is divalent with the missing H atoms replaced by metal atoms. The most likely decomposition pathway of ethanol on Pd(110) is CH(3)CH(2)OH → CH(3)CH(2)O → CH(3)CHO → CH(3)CO → CH(3) + CO → CO + H + CH(4) + C, in which the initial dehydrogenation is the rate-limited step. No C-O scission pathway is identified. Comparing with ethanol decomposition on Pd(111) [Langmuir, 2010, 26, 1879-1888], Pd(110) characterizes relatively high activity and different selectivity. Two crucial factors controlling the variations of reactivity and selectivity from Pd(111) to Pd(110), i.e., the local electronic effect of the metals and the geometrical effect of the relevant transition states, are identified. Four distinct Brønsted-Evans-Polanyi (BEP) relations are identified for the three types of bond scission (C-H, C-O, and C-C) if we consider Pd(111) and Pd(110) as a whole, one for C-H bond scission, one for C-O bond scission, and two for C-C bond scission.

Ethanol Electro-oxidation on Palladium Revisited Using Polarization Modulation Infrared Reflection Absorption Spectroscopy (PM-IRRAS) and Density Functional Theory (DFT): Why Is It Difficult To Break the C–C Bond?

“…78 The reaction selectivity toward acetic acid is better understood from the aforementioned reaction energy profiles, keeping in mind the C−H and O−H bond breaking in ethanol catalyzed by Pd have a barrier of <0.8 eV. 79 These steps can be even further activated by the presence of surface hydroxyls, as shown in previous DFT studies.…”

Interaction of intermediates with transition metal surfaces in the dehydrogenation of ethanol to ethyl acetate: A theoretical investigation

“…This is in total agreement with DFT and experimental observations. 20,23–25 The temperature-dependent studies showed that ethanol is adsorbed as ethoxy on unsupported polycrystalline Cu, preserving Cα–H and Cβ–H except O–H. 6…”

“…We initiate this section by considering routes highlighted in experimental and DFT findings about ethanol activation on TM surfaces. 20,[23][24][25] All likely bond scission paths include Ca-H, Cb-H and O-H in ethanol. We found after the computation of the activation energy for each pathway that there is a remarkable distinction among the different metals.…”

“…This is in total agreement with DFT and experimental observations. 20,[23][24][25] The temperature-dependent studies showed that ethanol is adsorbed as ethoxy on unsupported polycrystalline Cu, preserving Ca-H and Cb-H except O-H. 6 Nevertheless, some DFT investigations suggest Ca-H breakage over Pd and Pt(111), 26,27 while the adsorption-activation experiments indicated O-H bond cleavage. Even experimental results show discrepancies between the available studies concerning the scope of ethanol decomposition on Pt.…”

Experimental and Subsequent Mechanism Research on the Steam Reforming of Ethanol Over a Ni/CeO2Catalyst

“…While on Pd(111) surface, the most likely decomposition path on Pd(111) surface is CH 3 CH 2 OH * →CH 3 CH 2 O * →CH 3 CHO * →CH 3 CO * →CH 3 * + CO * , in which the initial dehydrogenation is the rate-limited step. (Alcala, Mavrikakis, and Dumesic 2003;Li et al 2010;Guo et al 2013). However, there are still no DFT calculations on the ethanol reforming reaction on a nickel-based catalyst surface.…”