Density Functional Theory Comparison of Methanol Decomposition and Reverse Reactions on Metal Surfaces

Abstract

Methanol decomposition on metals has been subject of several theoretical studies, usually concentrating on a particular set of reactions in the main reaction path. In this work, we present an extensive study that considers all potential elementary steps for four close-packed surfaces including Cu, Ru, Pt, and Pd that shows the different behaviors and alternative routes through which the decomposition can take place by theoretical methods, including dispersion contributions. Decomposition follows different paths on these metals; while Cu would produce CH 2 O, CO is the major product for the other metals. In addition, coverage effects might change the first step in Pt and Ru from methylenic to alcohol H activation. Alternatively the reaction network can be inspected for the formation of methanol from CO and hydrogen. Under these conditions, Cu generates CH 2 O and only at very high H coverages is methanol likely to appear. On Pd, methanol formation and CHOH dissociation compete, thus leading to an inefficient process. A similar path takes place for Pt. For Ru the lateral paths leading to C−O breaking can occur at several points in the reaction network, never reaching CH 3 OH. A compilation of the results with comparable computational setups presents a detailed database that can be added to the thermodynamics and kinetics for other reactions, such as methanation, with which they share a common list of reactions, or employed when analyzing larger alcohols such as those derived from biomass.

The Oxidation of Methanol on PtRu(111): A Periodic Density Functional Theory Investigation

“…For the methanol decomposition, the initial C−O bond scission is too hard to occur in general, while the O−H or C−H bond scission is favorable in different cases. For example, it proceeds preferably through the initial O−H bond scission on Ru(0001), 57 Cu(111), 57,77 and PtZn(111), 46 but the C−H bond scission is favorable on Pt(111) 54,57 and Pd(111). 57,69 To confirm the reaction network, we describe all the possible elementary steps in the methanol decomposition via both the initial O−H and C−H bond scissions.…”

“…45,58 Generally, the Pt(111) surface is the most stable crystal plane in Pt nanoparticles and thus is usually selected as the prototype in both experimental and theoretical investigations. 36,37,43,53,54,57 For comparison, the PtRu(111) surface was considered here. Furthermore, the PtRu(111) surface was computed with the fcc structure, which is the experimentally observed structure.…”

“…Indeed, under the initial conditions on the clean surfaces, methanol molecules would approach each other, and thus, a relatively high coverage can be reached even at medium pressures and low temperatures. 57 In addition, we also calculated the adsorption of CH 3 OH (Ru-top site) and CH 2 OH (Ru 2 -bridge site) on a larger (4 × 4) PtRu(111) cell. The relevant adsorption energies (E ads = −0.75 eV (CH 3 OH) and −2.22 eV (CH 2 OH)) were found to be slightly larger than that (−0.70 and −2.14 eV) calculated on the (2 × 2) cell, suggesting that the effect of surface coverage is not significant for adsorption.…”

Descriptor Analysis in Methanol Conversion on Doped CeO2(111): Guidelines for Selectivity Tuning

“…16,17 Starting from this early proposal, several alternative formulations that end up correlating with a single adsorption energy have been derived. [18][19][20][21][22][23] In particular, the transition state scaling (TSS) relationships correlate the transition state energy with the energy of the initial or the final state of the reaction.…”

Density functional theoretical studies on the methanol adsorption and decomposition on Ru(0001) surfaces

“…García-Muelas et al [13] investigated methanol decomposition on metals, including Cu, Ru, Pt and Pd, and found that decomposition follows different paths on these metals. On Ru(0001) surface, methanol decomposition initially begins from O-H bond cleavage to produce methoxy species that subsequently dehydrogenate to CO and hydrogen with no significant C-O bond breakage.…”