Oxidation of Hydrocarbons at Surface Defects: Unprecedented Confirmation of the Oxomethylidyne Pathway on a Stepped Rh Surface

Bhattacharjee, Tanushree; Inderwildi, Oliver R.; Jenkins, Stephen J.; Riedel, Uwe; Warnatz, Jürgen

doi:10.1021/jp8026594

Cited by 4 publications

(7 citation statements)

References 20 publications

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“…Based on the predicted reaction rates for each of the three CO formation paths (figure 5), the direct formation of CO from C-O coupling has the highest predicted rates at the top of the volcano, as compared to the hydrogen-assisted routes involving COH * and CHO * . This result is consistant with the theoretical work on metal (211) surfaces, which are conducted by Bengaard [27], Shetty [33] and Bhattacharjee [32], but contradictory to the results reported by Inderwildi [58], Wang [28,29] and Blaylock [30] on flat surfaces. There might be two reasons for the disparateness.…”

Section: Microkinetic Modelcontrasting

confidence: 82%

“…Moreover, a study by Bhattacharjee et al is consistent with experimental results suggesting that on a Rh(211) surface at high temperatures the formation of CO proceeds through the direct C-O combination pathway. At lower temperatures, however, a hydrogen insertion mechanisms involving COH * may be favorable [32]. Shetty et al studied both the direct and H-assisted pathway for CO formation on Ru(1121), showing that the direct CO formation pathway has a lower overall barrier [33].…”

Section: Introductionmentioning

confidence: 99%

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In silicosearch for novel methane steam reforming catalysts

Lausche

Wang

et al. 2013

New J. Phys.

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This paper demonstrates a method for screening transition metal and metal alloy catalysts based on their predicted rates and stabilities for a given catalytic reaction. This method involves combining reaction and activation energies (available to the public via a web-based application 'CatApp') with a microkinetic modeling technique to predict the rates and selectivities of a prospective material. This paper illustrates this screening technique using the steam reforming of methane to carbon monoxide and hydrogen as a test reaction. While catalysts are already commercially available for this process, the method demonstrated in this paper is very general and could be applied to a wide range 6

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Section: Microkinetic Modelcontrasting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

In silicosearch for novel methane steam reforming catalysts

Lausche

Wang

et al. 2013

New J. Phys.

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“…What seems safely established is that, relative to Rh{111}, the presence of steps at the Rh{211} surface reduces the barrier towards initial dissociative adsorption (0.32-0.42 eV on the stepped surface 38,114 vs. 0.67-0.72 eV on the flat 38,114,115 ), but does little to the barrier for methyl dissociation (0.40 eV on the stepped surface 114 vs. 0.42-0.49 eV on the flat 114,115 ). The barrier to methylene dissociation on Rh{211} is, at present, unknown, but methylidyne dissociation is activated by either 0.65 eV 129 or 1.04 eV, 130 both lower than the range of 1.18-1.28 eV on Rh{111}. Direct oxidation of methylidyne (CH) to formyl (CHO) is at least competitive with the carbidic route, and we believe it to be dominant.…”

Section: Rhodiummentioning

confidence: 91%

“…115,116 The barrier for the reaction is also substantially reduced, to just 0.65 eV, from values in the range 1.18-1.28 eV on the flat {111} surface. 114,115,121 In contrast, Bhattacharjee et al 130 have recently calculated a rather larger barrier of 1.04 eV for methylidyne dissociation on Rh{211}, finding lower barriers only if starting from adsorption geometries considerably less stable than the preferred fourfold hollow site. They therefore argue that oxidation on the stepped surface is, once again, unlikely to occur via a carbidic route.…”

Section: Rhodiummentioning

confidence: 94%

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In-silico investigations in heterogeneous catalysis—combustion and synthesis of small alkanes

Inderwildi

Jenkins

2008

Chem. Soc. Rev.

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In this critical review, we cover first-principles density functional calculations relevant to alkane oxidation and synthesis over transition metal catalysts. For oxidation, we focus upon Pt, Rh, Pd and Ni surfaces, while for synthesis we consider Co, Ru, Fe and Ni. Throughout, we emphasise the insight to be gained by thinking of each kind of reaction as the inverse of the other, with the directionality determined simply by the choice of metal catalyst and the reaction conditions. We highlight particularly the role of low-coordination sites (steps, kinks, etc.) and the emerging consensus over the importance of the formyl intermediate in facilitating the rate-determining step (249 references).

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Ethanol Synthesis from Syngas on the Stepped Rh(211) Surface: Effect of Surface Structure and Composition

et al. 2014

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The mechanisms of ethanol synthesis from syngas including CH x (x = 1−3) species and C 2 oxygenates on the stepped Rh(211) surface have been systematically investigated by using density functional theory together with a periodic slab model. Our results show that among all CH x (x = 1−3) species, CH 3 is the most favorable monomer, which is more favorable than CH 3 OH formation; this result is quite different from that on the flat Rh(111). Beginning with CH 3 species, CH 3 + CHO → CH 3 CHO dominantly contributes to the formation of C 2 oxygenates; subsequently, CH 3 CHO is successively hydrogenated to ethanol via CH 3 CH 2 O intermediate. Meanwhile, CH 4 formation by CH 3 hydrogenation is energetically compatible with CH 3 CHO formation; that is, the productivity and selectivity of ethanol is determined by the formations of CH 3 CHO and CH 4 . As a result, the strategy of improving the Rh-based catalyst with the help from the promoter Mn is employed to tune the relative activity of CH 3 CHO and CH 4 formations that control the productivity and selectivity of ethanol from syngas. Our results show that the productivity and selectivity of ethanol from syngas can be improved by introducing promoter Mn into the Rh catalyst.

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Oxidation of Hydrocarbons at Surface Defects: Unprecedented Confirmation of the Oxomethylidyne Pathway on a Stepped Rh Surface

Cited by 4 publications

References 20 publications

In silicosearch for novel methane steam reforming catalysts

In silicosearch for novel methane steam reforming catalysts

In-silico investigations in heterogeneous catalysis—combustion and synthesis of small alkanes

Ethanol Synthesis from Syngas on the Stepped Rh(211) Surface: Effect of Surface Structure and Composition

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