Insights on the reactivity of ordered porous carbons exposed to different fluorinating agents and conditions

Ghimbeu, Camélia Matei; Guérin, Katia; Dubois, Marc; Hajjar‐Garreau, Samar; Vix‐Guterl, Cathie

doi:10.1016/j.carbon.2014.12.034

Cited by 24 publications

(17 citation statements)

References 71 publications

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“…The specific surface area decreases significantly due to the decrease of the smallest pores of the resulting material. This modification of the carbon texture during the fluorination (even if the level is low) could be compared to a strong activation phenomenon with the likely formation and exhausting of gaseous CF 4 or C 2 F 6 [34,35]. This behavior has been observed also during the fluorination of template mesoporous carbon by diluted fluorine gas [31].…”

Section: Resultsmentioning

confidence: 86%

First Insight into Fluorinated Pt/Carbon Aerogels as More Corrosion-Resistant Electrocatalysts for Proton Exchange Membrane Fuel Cell Cathodes

et al. 2015

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International audienceThis study evaluates the fluorination of a carbon aerogel and gives first insights into its durability when used as platinum electrocatalyst substrate for proton exchange membrane fuel cell (PEMFC) cathodes. Fluorine has been introduced before or after platinum deposition. The different electrocatalysts are physico-chemically and electrochemically characterized, and the results discussed by comparison with commercial Pt/XC72 from E-Tek. The results demonstrate that the level of fluorination of the carbon aerogel can be controlled. The fluorination modifies the texture of the carbons by increasing the pore size and decreasing the specific surface area, but the textures remain appropriate for PEMFC applications. Two fluorination sites are observed, leading to both high covalent C-F bonds and weakened ones, the quantity of which depends on whether the treatment is done before or after platinum deposition. The order of the different treatments is very important. Indeed, the presence of platinum contributes to the fluorination mechanism, but leads to amorphous platinum, which is demonstrated rather inactive towards the oxygen reduction reaction. On the contrary, a better durability was demonstrated for the fluorinated and then platinized catalyst compared both to the same but not fluorinated catalyst and to the reference commercial material (based on the loss of the electrochemical real surface area after accelerated stress tests)

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Section: Resultsmentioning

confidence: 86%

First Insight into Fluorinated Pt/Carbon Aerogels as More Corrosion-Resistant Electrocatalysts for Proton Exchange Membrane Fuel Cell Cathodes

et al. 2015

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“…The desorption is not completed at 700 K and is attributed to partial desorption from bulklike MgH 2 and/or desorption from the carbon scaffold occurring at high temperature. 22 It is obvious from the TDS results that the hydrogen desorption kinetics of all MgH 2 @CT composites is noticeably faster than that of bulk MgH 2 . This can be accounted for by the shorter diffusion length of hydrogen within the nanoparticles, compared to the bulk.…”

Section: ■ Results and Discussionmentioning

confidence: 90%

Ultrasmall MgH₂ Nanoparticles Embedded in an Ordered Microporous Carbon Exhibiting Rapid Hydrogen Sorption Kinetics

et al. 2015

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MgH2 nanoparticles with different average sizes have been prepared as ordered microporous carbon by tuning the Mg amount from 15 to 50 wt %. Ultrasmall particles with mean sizes of 1.3 and 3.0 nm have been obtained for 15 and 25 wt % Mg contents, respectively. The hydrogen desorption properties strongly depend on the nanoparticle size, as evidenced by different thermal analysis techniques. The onset temperature of hydrogen desorption for MgH2 nanoparticles below 3 nm occurs at a temperature about 245 K lower than for microcrystalline material. Two distinct hydrogen desorption peaks are noticed for nanoparticles with mean sizes of 1.3 and 3.0 nm, as confirmed by TDS and HP-DSC. 1H NMR investigations suggest the presence of two MgH2 populations with enhanced hydrogen mobility, as compared to the microcrystalline hydride. The short hydrogen diffusion path and the enhanced hydrogen mobility may explain the increased desorption kinetics of these ultrasmall nanoparticles.

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“…In this regard, some C-H and C-C bonds can be broken during the fluorination process, forming dangling bonds, which are likely to subsequently react with oxygen and moisture from air and form oxygenated surface groups (Dubois et al, 2018 ). The presence of oxygenated groups in the starting material may also affect the nature and stability of the C–F bonding (Matei Ghimbeu et al, 2015 ). On the other hand, samples B and D exhibit a similar surface composition, thus indicating a low impact of the temperature in the extent of the fluorination.…”

Section: Resultsmentioning

confidence: 99%

“…The doping of carbon materials with heteroelements is known to be an effective approach to tailor their hydrophilic/hydrophobic character and consequently their water adsorption behavior (Lee et al, 2007 ; Kumar et al, 2016 ). In this regard, fluorinated porous carbonaceous materials are receiving increasing attention due to their promising performance in several fields such as gas adsorption, gas sensors or energy storage (Touhara and Okino, 2000 ; Park et al, 2016 ; Kim et al, 2018 ; Wang et al, 2020 ) and they can even be considered as a new class of materials (Matei Ghimbeu et al, 2015 ; Shahtalebi et al, 2016 ). In the specific case of activated carbon fibers, fluorination has proven effective for improving their electrochemical properties (Shao et al, 2016 ) as well as the methane storage capacity (Im et al, 2009 ), CO 2 adsorption (Sugiyama and Hattori, 2020 ), and even for biomedical applications (Sun et al, 2017 ).…”

Section: Introductionmentioning

confidence: 99%

“…It has to be taken into account that besides the fluorination conditions (fluorine agent, temperature, reaction time…), the final chemical composition, as well as the structure of the products obtained by fluorination, are dependent on the structure and characteristics of the starting material (e.g. degree of graphitization, structural order, dimensions of the particles, surface curvature, purity…) (Lee et al, 2007 ; Matei Ghimbeu et al, 2015 ).…”

Section: Introductionmentioning

confidence: 99%

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Influence of Fluorine Doping of Activated Carbon Fibers on Their Water Vapor Adsorption Characteristics

et al. 2021

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The characterization of fluorinated carbon fibers by water sorption has been broadly investigated in this work. In brief, a pitch-based activated carbon fiber (ACF) was submitted to a fluorination process under different conditions of partial pressure (F2:N2 ratio) and temperature. This led to samples with varied fluorine content and C-F type bonding. The effect of the fluorination treatment on the textural properties of the ACF was studied by means of nitrogen and carbon dioxide adsorption at −196 and 0°C, respectively, while the changes induced in the surface chemistry of the materials were analyzed by XPS. Also, the affinity and stability of the materials toward water was evaluated by single and cycling isotherms. The obtained results show that a mild fluorination not only can preserve most of the textural properties of the parent ACF, but enhance the water uptake at the first stages of the water sorption process, together with a shift in the upswing of the water isotherms toward lower relative humidities. This indicates that fluorination under certain conditions can actually enhance the surface hydrophilicity of carbon materials with specific properties. On the contrary, higher partial pressures led to highly fluorinated fibers with lower porosity and more hydrophobic character. Moreover, they presented a lower chemical stability as demonstrated by a change in the shape of the water isotherms after two consecutive measurements. The kinetics of water sorption in the ACFs provided further insights into the different sorption phenomena involved. Hence, water sorption can definitely help to tailor the water affinity, stability and performance of fluorinated porous carbon materials under humid conditions.

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Insights on the reactivity of ordered porous carbons exposed to different fluorinating agents and conditions

Cited by 24 publications

References 71 publications

First Insight into Fluorinated Pt/Carbon Aerogels as More Corrosion-Resistant Electrocatalysts for Proton Exchange Membrane Fuel Cell Cathodes

First Insight into Fluorinated Pt/Carbon Aerogels as More Corrosion-Resistant Electrocatalysts for Proton Exchange Membrane Fuel Cell Cathodes

Ultrasmall MgH₂ Nanoparticles Embedded in an Ordered Microporous Carbon Exhibiting Rapid Hydrogen Sorption Kinetics

Influence of Fluorine Doping of Activated Carbon Fibers on Their Water Vapor Adsorption Characteristics

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Insights on the reactivity of ordered porous carbons exposed to different fluorinating agents and conditions

Cited by 24 publications

References 71 publications

First Insight into Fluorinated Pt/Carbon Aerogels as More Corrosion-Resistant Electrocatalysts for Proton Exchange Membrane Fuel Cell Cathodes

First Insight into Fluorinated Pt/Carbon Aerogels as More Corrosion-Resistant Electrocatalysts for Proton Exchange Membrane Fuel Cell Cathodes

Ultrasmall MgH2 Nanoparticles Embedded in an Ordered Microporous Carbon Exhibiting Rapid Hydrogen Sorption Kinetics

Influence of Fluorine Doping of Activated Carbon Fibers on Their Water Vapor Adsorption Characteristics

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Ultrasmall MgH₂ Nanoparticles Embedded in an Ordered Microporous Carbon Exhibiting Rapid Hydrogen Sorption Kinetics