Ammonia decomposition on Fe(1 1 0), Co(1 1 1) and Ni(1 1 1) surfaces: A density functional theory study

Duan, Xuezhi; Ji, Jian; Qian, Gang; Fan, Chen; Zhu, Yi‐An; Chen, De; Wang, Yuan

doi:10.1016/j.molcata.2012.01.023

Cited by 120 publications

(119 citation statements)

References 42 publications

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“…1, along with the corresponding geometrical parameters. An NH 3 molecule is preferentially adsorbed in a top configuration, consistent with previous theoretical studies of NH 3 adsorption over different surfaces [18,[36][37][38][39][40]. All attempts to find any other type local minimum led to the top one after complete optimization.…”

Section: Resultssupporting

confidence: 86%

“…H. This is significantly larger than the corresponding barriers on Pt(111) (32 kcal/mol) and Pt(100) (24 kcal/mol) [48]. In light of the relatively high reaction barrier and the endothermicity of this reaction, it is thus expected that the dissociation of NH fragment on SiCNT is unfavorable both kinetically and thermodynamically, which is consistent with the other theoretical results [36][37][38].…”

Section: Resultssupporting

confidence: 85%

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Catalytic decomposition of ammonia over silicon-carbide nanotube: a DFT study

Esrafili

Nurazar

2014

Struct Chem

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Decomposition of ammonia is important for a series of technological and environmental applications. For developing highly active catalysts for this reaction, detailed understanding of underlying mechanisms remains a challenge. In this work, density functional theory calculations are performed to investigate the adsorption and catalytic decomposition of NH 3 molecule on a pristine silicon-carbide nanotube (SiCNT) surface. The adsorption energy of a possible stable configuration and the activation energies for elementary reactions involved are obtained in the present study. It is found that ammonia experiences a chemisorption interaction with the SiCNT surface, with a significant alter in its structure with respect to the gas-phase molecule. Subsequently, the coadsorption of two ammonia molecules on the SiCNT surface is studied and the catalytic dehydrogenation reactions are considered. The catalytic activity of SiCNT surface in the decomposition reaction of NH 3 molecules is slightly altered due to locally adsorbed NH 3 . The reaction energies and the activation barriers obtained suggest that for the decomposition of ammonia molecules into N 2 H 2 , the rate-determining step is the NH 2 ?NH ? H reaction. As a result, the NH 2 is the dominant surface species after the SiCNT surface is exposed to NH 3 .

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Section: Resultssupporting

confidence: 86%

Section: Resultssupporting

confidence: 85%

Catalytic decomposition of ammonia over silicon-carbide nanotube: a DFT study

Esrafili

Nurazar

2014

Struct Chem

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“…For example, the close packed Ni (111) surface is believed to have a much higher ammonia decomposition activity than the stepped Ni (211) surface, with a similar configuration to the Ru step sites rich in B5 sites, as the latter is easily blocked by adsorbed nitrogen adatoms [35]. Similar effects are observed for other 3d-late transition metals such as Fe or Co [36]. Indeed, it has been suggested that C7 sites present in smaller particles are more active than large crystallites in iron-based systems [37], which seems to be in agreement with the work presented herein.…”

Section: Resultsmentioning

confidence: 82%

Ammonia decomposition over cobalt/carbon catalysts—Effect of carbon support and electron donating promoter on activity

2017

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Please cite this article in press as: L. Torrente-Murciano, et al., Ammonia decomposition over cobalt/carbon catalysts-Effect of carbon support and electron donating promoter on activity, Catal. Today (2016), http://dx. a b s t r a c tThis paper sets the new design parameters for the development of low temperature ammonia decomposition catalysts based on readily available cobalt as an alternative to scarce but highly active ruthenium-based catalysts. By using a variety of carbon materials as catalytic supports, we systematically demonstrate that microporous supports capable of stabilising small cobalt crystallites (∼2 nm) lead to high catalytic activities compared to bigger nanoparticles. Additionally, the degree of graphitisation of the carbon support has a detrimental effect on the activity of the cobalt (0) active sites, likely due to their potential as an electron donator. Consequently, the addition of electron donating promoters such as cesium substantially decreases the activity of the cobalt catalysts. This relationship deviates from the trends observed for ruthenium-based catalysts with an optimum 3-5 nm size where an increase of the graphitisation degree of the support and the addition of electron donating promoters increases the ammonia decomposition activity.

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“…A DFT theoretical study by Duan et al [32] calculated the activation energy and adsorption energies of reaction intermediates on Fe (110), Co (111) and Ni (111) closepacked surfaces during ammonia decomposition. The results showed that the adsorption energy of NH 3 onto Co and Ni is lower than on Fe and Fe has the highest activation energy, agreeing with experimental observations of ironbased catalysts generally having the lowest activity compared to cobalt-and nickel-based catalysts.…”

Section: Monometallic Systemsmentioning

confidence: 99%

H2 Production via Ammonia Decomposition Using Non-Noble Metal Catalysts: A Review

2016

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The wide-spread implementation of the so-called hydrogen economy is currently partially limited by an economically feasible way of storing hydrogen. In this context, ammonia has been commonly presented as a viable option for chemical storage due its high hydrogen content (17.6 wt%). However, its use as an energy carrier requires the development of catalytic systems capable of releasing hydrogen at adequate rates and conditions. At the moment, the most active catalytic systems for the decomposition of ammonia are based on ruthenium, however its cost and scarcity inhibit the wide scale use of these catalysts. This issue has triggered research on the development of alternative catalysts based on more sustainable systems using more readily available, non-noble metals mainly iron, cobalt and nickel as well as a series of transition metal carbides and nitrides and bimetallic systems, which are reviewed herein. There have been some promising cobaltand nickel-based catalysts reported for the decomposition of ammonia but metal dispersion needs to be increased in order to become more attractive candidates. Conversely, there seems to be less scope for improvement of iron-based catalysts and metal carbides and nitrides. The area with the most potential for improvement is with bimetallic catalysts, particularly those consisting of cobalt and molybdenum.

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Ammonia decomposition on Fe(1 1 0), Co(1 1 1) and Ni(1 1 1) surfaces: A density functional theory study

Cited by 120 publications

References 42 publications

Catalytic decomposition of ammonia over silicon-carbide nanotube: a DFT study

Catalytic decomposition of ammonia over silicon-carbide nanotube: a DFT study

Ammonia decomposition over cobalt/carbon catalysts—Effect of carbon support and electron donating promoter on activity

H2 Production via Ammonia Decomposition Using Non-Noble Metal Catalysts: A Review

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