Monitoring water and oxygen splitting at graphene edges and folds: Insights into the lubricity of graphitic materials

Restuccia, Paolo; Ferrario, Mauro; Righi, Maria Clelia

doi:10.1016/j.carbon.2019.09.040

Cited by 47 publications

(27 citation statements)

References 107 publications

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“…It has been reported that the surface of HOPG cleaved using adhesive tape presented steps, and the edges of the steps were formed by graphene layers that broke during peeling; 17 moreover, the formed step edges of the graphene layers that reacted with atmospheric oxygen and oxygenated carbon species were produced 17 . Furthermore, the quantum mechanics/molecular mechanics and density functional theory approaches confirmed the formation of CH, COH, and CO bonds via the reaction of the graphene edges with water molecules 29,30 …”

Section: Resultsmentioning

confidence: 89%

“…17 Furthermore, the quantum mechanics/molecular mechanics and density functional theory approaches confirmed the formation of C H, C OH, and C O bonds via the reaction of the graphene edges with water molecules. 29,30 Hence, using the above-mentioned EELS analysis results and literature-reported data, it was suggested that the adhesive tapeexfoliated HOPG presented a roughened surface with disordered graphene layers which reacted with atmospheric oxygen and water molecules. It is of great importance that the difference in the surface and internal structure of HOPG including the chemical bond can be clarified at the atomic level through the HRTEM observation combined with the STEM-EELS measurement by using the crosssectioned HOPG sample.…”

Section: Resultsmentioning

confidence: 95%

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Cross‐sectional structural characterization of the surface of exfoliated HOPG using HRTEM‐EELS

Miyazawa

Nagai

Kimoto

et al. 2020

Surface & Interface Analysis

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We analyzed the surface atomic structure of highly oriented pyrolytic graphite (HOPG) substrate exfoliated with adhesive tape, using high-resolution transmission electron microscopy and scanning transmission electron microscopy-electron energyloss spectroscopy (STEM-EELS). The surface step height of the exfoliated HOPG substrate was determined using high-angle annular dark-field-scanning transmission electron microscopy (HAADF-STEM) images and the depth profiles of the EELS spectra of a cross-sectioned thin foil specimen prepared via focused ion beam milling. The exfoliated surface of the HOPG substrate presented disordered and curved graphene layers. The STEM-EELS measurements indicated that upon exfoliation, the surface of the HOPG substrate reacted with atmospheric water and oxygen molecules.

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Section: Resultsmentioning

confidence: 89%

Section: Resultsmentioning

confidence: 95%

Cross‐sectional structural characterization of the surface of exfoliated HOPG using HRTEM‐EELS

Miyazawa

Nagai

Kimoto

et al. 2020

Surface & Interface Analysis

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“…Indeed, it has been shown that dioxygen reacts easily with carbon vacancies, to form less reactive ether or carbonyl groups. [ 59 ] For a similar reason, we avoid using water [ 60 ] or potentially reactive alcoholic solvent [ 61 ] for the impregnation step, and prefer pentane. On the other hand, we have chosen to use organometallic precursors in the zero oxidation state for the impregnation because of their potentially higher reactivity compared to metal salts.…”

Section: Resultsmentioning

confidence: 99%

Stabilization of Metal Single Atoms on Carbon and TiO₂ Supports for CO₂ Hydrogenation: The Importance of Regulating Charge Transfer

Rivera‐Cárcamo

Scarfiello

Garcı́a

et al. 2020

Adv Materials Inter

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Supported single atoms constitute excellent models for understanding heterogenous catalysis and have achieved breakthroughs during the past years. How to prevent the aggregation and modulate activity of these species via metal‐support interaction should be considered for practical applications. This work presents simple methods involving the creation of carbon‐ (on carbon nanotube (CNT)) or oxygen‐vacancies (on TiO2) to stabilize nickel and ruthenium single atoms. The defective supports and the resulting catalysts are characterized by a large variety of techniques. These analyses show that this strategy is efficient for the preparation of ultra‐dispersed catalysts. Comparison of the catalytic performances of these catalysts for the CO2 hydrogenation reaction is also reported. Catalysts supported on TiO2 are more active and sometimes more stable than those deposited on CNT. Nickel catalysts are very selective for the production of CO, and ruthenium catalysts are more selective for the production of methane. Most importantly, it is shown that, in the case of Ru, a direct correlation exists between the electronic density on the metal and the selectivity; electron‐rich species produce selectively methane, while electron‐deficient species orientate the selectivity toward CO. This work may figure a new way for the synthesis of ultra‐dispersed catalysts for various applications.

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“…This in-plane interaction is responsible for the decrease of adhesion observed when two P-covered surfaces are brought into contact. The next step in our analysis of the tribochemistry of organophosfurus additives will be to consider a larger amount of additive molecules in our supercell to monitor in real applied for the first time to tribology by our group, [45] will allow us to face this computational challenge.…”

Section: Discussionmentioning

confidence: 99%

<em>Ab Initio</em> Molecular Dynamics Simulation of Tribochemical Reactions Involving Phosphorus Additives at Sliding Iron Interfaces

Loehlé¹,

Righi²

2018

Preprint

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We performed for the first time to our knowledge fully ab initio molecular dynamics simulations of additive tribochemistry in boundary lubrication conditions. We consider an organophosphourus additive that has been experimentally shown to reduce friction in steel-on-steel sliding contacts thanks to the tribologically-induced formation of an iron phosphide tribofilm. The simulations allow us to observe in real time the molecular dissociation at the sliding iron interface under pressure and to understand the mechanism of iron phosphide formation. We discuss the role played by the mechanical stress by comparing the activation times for molecular dissociation observed in the tribological simulations at different applied loads with that expected on the basis of the dissociation barrier.

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Monitoring water and oxygen splitting at graphene edges and folds: Insights into the lubricity of graphitic materials

Cited by 47 publications

References 107 publications

Cross‐sectional structural characterization of the surface of exfoliated HOPG using HRTEM‐EELS

Cross‐sectional structural characterization of the surface of exfoliated HOPG using HRTEM‐EELS

Stabilization of Metal Single Atoms on Carbon and TiO₂ Supports for CO₂ Hydrogenation: The Importance of Regulating Charge Transfer

<em>Ab Initio</em> Molecular Dynamics Simulation of Tribochemical Reactions Involving Phosphorus Additives at Sliding Iron Interfaces

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Monitoring water and oxygen splitting at graphene edges and folds: Insights into the lubricity of graphitic materials

Cited by 47 publications

References 107 publications

Cross‐sectional structural characterization of the surface of exfoliated HOPG using HRTEM‐EELS

Cross‐sectional structural characterization of the surface of exfoliated HOPG using HRTEM‐EELS

Stabilization of Metal Single Atoms on Carbon and TiO2 Supports for CO2 Hydrogenation: The Importance of Regulating Charge Transfer

<em>Ab Initio</em> Molecular Dynamics Simulation of Tribochemical Reactions Involving Phosphorus Additives at Sliding Iron Interfaces

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Stabilization of Metal Single Atoms on Carbon and TiO₂ Supports for CO₂ Hydrogenation: The Importance of Regulating Charge Transfer