Pathways for methanol steam reforming involving adsorbed formaldehyde and hydroxyl intermediates on Cu(111): density functional theory studies

Abstract

Plane-wave density functional theory calculations have been carried out to explore possible pathways in methanol steam reforming (MSR) on Cu(111). We focus on reactions involving the adsorbed formaldehyde intermediate (CH(2)O) produced by methanol decomposition and the surface hydroxyl (OH) species generated by dissociative adsorption of H(2)O. Several possible pathways leading to the H(2) + CO(2) products have been identified. The two most likely pathways involve the formate (CHOO), rather than the carboxyl (COOH), intermediate, and they possess barriers lower than that of the rate-limiting step of MSR, namely the dehydrogenation of adsorbed methoxyl (CH(3)O) species.

Theoretical Insight into the Reaction Mechanism of Ethanol Steam Reforming on Co(0001)

“…This reaction is analogous to the formation of CH 2 OOH* from formaldehyde (CH 2 O*) and hydroxyl (OH*) in MSR on Cu and PdZn, which was the key to the CO 2 selectivity. 26,30 The barrier for this step is 0.68 eV, much higher than those for the formation of CH 2 OOH* on PdZn (0.16 eV) and Cu (0.11 eV), 28,30 but close to that of the same reaction (0.86 eV without the ZPE correction) on Co(0001). 32 This process is nearly thermoneutral with ΔE equal to 0.06 eV.…”

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.…”

An Atomic Scale View of Methanol Reactivity at the Cu(1 1 1)/CuOx Interface

“…[1,5,10] The industrial catalysts for MeOH synthesis and MeOH steam reforming are Cu-based materials. [3,9,[11][12][13][14] In contrast to the highly reactive Pt, Pd metal, and FeO x surfaces, [15][16][17][18][19][20][21] clean Cu(111) surfaces adsorb MeOH molecularly without any decomposition. [22][23][24] The decomposition of MeOH on Cu is facilitated by the presence of oxygen and it occurs via a methoxy (MeO) species.…”

“…[1,3,5,6] MeOH is a key feedstock in the production of chemicals such as formaldehyde and acetic acid [3,7,8] and is also used in the production of hydrogen through its decomposition, steam reforming, and partial oxidation reactions. [1,3,9] MeOH is widely considered an attractive alternative fuel compared to H 2 because of its transportation properties: it is a liquid fuel, has low toxicity compared to gasoline and diesel fuels, and can be produced by various sources, such as syngas and renewable biomass. [5,8] The high H/C ratio (4:1), equal to that of methane, makes it an important energy carrier.…”