Structure-dependent adsorption and desorption of hydrogen on FCC and HCP cobalt surfaces

Weststrate, C.J.; Rodríguez, Daniel García; Sharma, Devyani; Niemantsverdriet, J.W.

doi:10.1016/j.jcat.2021.12.016

Cited by 12 publications

(7 citation statements)

References 46 publications

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“…Such a difference in adsorption capability between Co hcp and fcc is also observed in hydrogen adsorption. H 2 desorption peak on Co fcc (100) surface is observed at 260 K. On the other hand, H 2 desorption peak on Co hcp (0001) surface appears at 350 K . This may be attributed to strongly spin-polarized Co hcp; the polarized d-bond of Co 3d orbitals crosses the Fermi level .…”

Section: Resultsmentioning

confidence: 95%

Tuning the Selectivity of Catalytic Nitrile Hydrogenation with Phase-Controlled Co Nanoparticles Prepared by Hydrosilane-Assisted Method

Jiang,

Deng,

Kita

et al. 2024

J. Am. Chem. Soc.

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Cobalt (Co) is a promising candidate to replace noble metals in the hydrogenation process, which is widely employed in the chemical industry. Although the catalytic performance for this reaction has been considered to be significantly dependent on the Co crystal phase, no satisfactory systematic studies have been conducted, because it is difficult to synthesize metal nanoparticles that have different crystalline structures with similar sizes. Here we report a new method for the synthesis of cobalt nanoparticles using hydrosilane as a reducing agent (hydrosilane-assisted method). This new method uses 1,3-butanediol and propylene glycol to successfully prepare fcc and hcp cobalt nanoparticles, respectively. These two types of Co nanoparticles have similar sizes and surface areas. The hcp Co nanoparticles exhibit higher catalytic performance than fcc nanoparticles for the hydrogenation of benzonitrile under mild conditions. The present hcp Co catalyst is also effective for highly selective benzyl amine production from benzonitrile without ammonia addition, whereas many catalytic systems require ammonia addition for selective benzyl amine production. Mechanistic studies revealed that the fast formation of the primary amine and the prevention of condensation and secondary amine hydrogenation promote selective benzonitrile hydrogenation for benzylamine over hcp Co nanoparticles.

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Section: Resultsmentioning

confidence: 95%

Tuning the Selectivity of Catalytic Nitrile Hydrogenation with Phase-Controlled Co Nanoparticles Prepared by Hydrosilane-Assisted Method

Jiang,

Deng,

Kita

et al. 2024

J. Am. Chem. Soc.

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“…231 Step and kink sites might increase H* coverage, but this also results in desorption at lower temperatures by providing a low-energy path for both adsorption and desorption. 232 Comparison of the adsorption strengths on the most common cobalt surface facets suggests hydrogen adsorption is favored on the 3-fold hollow sites of close-packed terraces. Under FT conditions, other species will be present, affecting this hydrogen coverage and vice versa.…”

Section: Surface Science and Experimental Mechanistic Studiesmentioning

confidence: 99%

“…Investigation of the TPD spectra of the closepacked Co(0001) and more open Co(1120) and Co(1012) surfaces showed that low-coordinated sites facilitate H 2 dissociation, suggesting the importance of step and kink sites in this reaction 231. Step and kink sites might increase H* coverage, but this also results in desorption at lower temperatures by providing a low-energy path for both adsorption and desorption 232. Comparison of the adsorption strengths on the most common cobalt surface facets suggests hydrogen adsorption is favored on the 3-fold hollow sites of close-packed terraces.…”

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confidence: 99%

Molecular Views on Fischer–Tropsch Synthesis

Rommens

Saeys

2023

Chem. Rev.

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For nearly a century, the Fischer–Tropsch (FT) reaction has been subject of intense debate. Various molecular views on the active sites and on the reaction mechanism have been presented for both Co- and Fe-based FT reactions. In the last 15 years, the emergence of a surface-science- and molecular-modeling-based bottom-up approach has brought this molecular picture a step closer. Theoretical models provided a structural picture of the Co catalyst particles. Recent surface science experiments and density functional theory (DFT) calculations highlighted the importance of realistic surface coverages, which can induce surface reconstruction and impact the stability of reaction intermediates. For Co-based FTS, detailed microkinetic simulations and mechanistic experiments are moving toward a consensus about the active sites and the reaction mechanism. The dynamic phase evolution of Fe-based catalysts under the reaction conditions complicates identification of the surface structure and the active sites. New techniques can help tackle the combinatorial complexity in these systems. Experimental and DFT studies have addressed the mechanism for Fe-based catalysts; the absence of a clear molecular picture of the active sites, however, limits the development of a molecular view of the mechanism. Finally, direct CO2 hydrogenation to long-chain hydrocarbons could present a sustainable pathway for FT synthesis.

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“…When the cobalt particle size decreased below 20 nm, the ratio exceeded 1.5, and the strong hydrogen binding sites dominated the catalyst surface. This is due to the multiplication of undercoordinated structures of cobalt, such as close-packed terraces, steps, and kinks at the cost of open surfaces [147], which bind H 2 hydrogen stronger than flat surfaces [148,149]. This trade-off leads to the hydrogen poisoning of the catalysts, limiting their activity.…”

Section: Cobalt-based Catalystsmentioning

confidence: 99%

Lanthanide Oxides in Ammonia Synthesis Catalysts: A Comprehensive Review

Patkowski,

Zybert,

Ronduda

et al. 2023

Catalysts

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The production of ammonia through the Haber–Bosch process is a large-scale catalytic industrial endeavour with substantial energy consumption. A key area of energy optimisation for this process involves efforts to ease the synthesis reaction conditions, particularly by reducing the operating pressure. To achieve this goal, new catalysts are designed to function effectively at lower pressures and temperatures. In recent years, reports in the literature concerning including lanthanide oxides in the catalysts’ composition have started appearing more frequently. This review article offers a concise overview of the pivotal role that lanthanide oxides play in the field of ammonia synthesis catalysts. The paper delves into the diverse utilisation of lanthanide oxides, emphasising their role in catalytic systems. The review explores recent advances in the design of catalysts incorporating lanthanide oxides as promoters or support materials, highlighting their impact on enhancing catalyst stability, activity, and operation. Three main groups of catalysts are discussed, where iron, ruthenium, and cobalt constitute the active phase. Insights from recent research efforts are synthesised to provide a comprehensive perspective on the application prospects of lanthanide oxides in ammonia synthesis catalysts.

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Structure-dependent adsorption and desorption of hydrogen on FCC and HCP cobalt surfaces

Cited by 12 publications

References 46 publications

Tuning the Selectivity of Catalytic Nitrile Hydrogenation with Phase-Controlled Co Nanoparticles Prepared by Hydrosilane-Assisted Method

Tuning the Selectivity of Catalytic Nitrile Hydrogenation with Phase-Controlled Co Nanoparticles Prepared by Hydrosilane-Assisted Method

Molecular Views on Fischer–Tropsch Synthesis

Lanthanide Oxides in Ammonia Synthesis Catalysts: A Comprehensive Review

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