The influence of oxidation on the texture and the number of oxygen-containing surface groups of carbon nanofibers

Toebes, Marjolein L.; Heeswijk, Jürgen M.P van; Bitter, Johannes H.; Dillen, A.J. van; Jong, Krijn P. de

doi:10.1016/j.carbon.2003.10.036

Cited by 351 publications

(302 citation statements)

References 23 publications

(49 reference statements)

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“…Next, the CNF were grown at 823 K in a mixture of CO (80 mL/min), H 2 (28 mL/ min), and Ar (292 mL/min) for 24 h. A more detailed description of the growth catalyst and the growth of the CNF can be found elsewhere. 36 Activation and Pretreatment of CNF. All CNF samples were refluxed for 1 h in a 1 M KOH solution in order to remove the silica support.…”

Section: Methodsmentioning

confidence: 99%

Preparation of Carbon Nanofiber Supported Platinum and Ruthenium Catalysts: Comparison of Ion Adsorption and Homogeneous Deposition Precipitation

et al. 2004

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Carbon nanofiber (CNF) supported platinum catalysts have been prepared using Pt(NH 3 ) 4 (NO 3 ) 2 as a precursor by two different ion adsorption techniques, one at a constant pH and one in which the pH is gradually and homogeneously increased from 3 to 6 by hydrolysis of urea. The latter method resembles the procedure of homogeneous deposition precipitation (HDP). Characterization of the CNF support was performed by acidbase titration, thermogravimetric mass spectrometry, and X-ray photoelectron spectroscopy, and for the various platinum catalysts, transmission electron microscopy, H 2 -chemisorption, and X-ray fluorescence/inductively coupled plasma-atomic emission spectrometry were utilized. With both synthesis techniques from diluted precursor solutions homogeneously distributed, highly dispersed and thermally stable metal particles were obtained with an average particle size of 1-2 nm. With the HDP method for the Pt/CNF catalysts, a linear relationship between the number of acidic oxygen-containing groups on the surface of activated CNF and the metal loading has been found. For the highest loaded catalyst, a platinum/adsorption site ratio of 0.5 was established, corresponding to about 0.7 Pt(NH 3 ) 4 2+ molecules/nm 2 . Furthermore, it has been established that with this procedure higher platinum loadings (∼4 wt %) can be achieved than with the ion adsorption procedure (<2 wt %). The HDP method using RuNO(NO 3 ) 3 (H 2 O) 2 also turned out to be suitable for the preparation of small (1-2 nm) uniform ruthenium particles on CNF with a high thermostability.

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Section: Methodsmentioning

confidence: 99%

Preparation of Carbon Nanofiber Supported Platinum and Ruthenium Catalysts: Comparison of Ion Adsorption and Homogeneous Deposition Precipitation

et al. 2004

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“…To change the concentration of oxygen-containing groups on the CNF surface, samples of the freshly reduced catalyst were heattreated in a nitrogen atmosphere for 2 h to vary the amount of oxygen-containing groups. In this study also, a catalyst treated at 500°C was investigated (O/C atomic ratio of 0.026, 33 further indicated as Pt/CNF500). The catalyst samples together with their identification codes are listed in Table 1. 2.2.…”

Section: Synthesis Of Carbon-supported Platinum Catalystsmentioning

confidence: 99%

Metal Particle Size and Structure of the Metal−Support Interface of Carbon-Supported Platinum Catalysts as Determined with EXAFS Spectroscopy

et al. 2004

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The metal particle size and structure of the metal-support interface of platinum supported on Vulcan XC-72 (a commercial catalyst used in platinum fuel-cell electrodes) and on carbon nanofibers (CNF) have been determined with extended X-ray absorption fine structure spectroscopy (EXAFS). The CNF-supported Pt catalysts were synthesized using a homogeneous deposition precipitation (HDP) method. The amount of acidic oxygen groups on the CNF surface was modified by treatment in an inert atmosphere at different temperatures. The average first shell Pt-Pt coordination number (∼5.5) detected in Pt/CNF is much smaller than for Pt/ Vulcan XC-72 (∼8.2). The presence of oxygen-containing groups in the CNF support most probably leads to the stabilization of small Pt particles on the CNF support. A prominent interaction between the metal particles and the support atoms was detected on both kinds of catalysts, which confirms that the metal is in direct contact with the carbon support atoms. After reduction, a long metal-carbon distance around 2.62 Å was detected in both Pt/Vulcan XC-72 and Pt/CNF. After evacuation of Pt/CNF at higher temperatures, the distance between support and interfacial metal atoms decreased to 2.02 Å. Therefore, the long metal-carbon support distance is ascribed to the presence of atomic chemisorbed hydrogen in the interface between the Pt particles and the carbon support. According to the number of interfacial Pt-C bonds (four), the platinum particles supported on CNF are proposed to be in contact with a prismatic surface of the carbon support, on which oxygen groups have more stable bonds with carbon atoms. Six Pt-C bonds could be detected in the metal-support interface of Pt/Vulcan XC-72 with an even longer carbon shell at 3.62 Å, indicating that the metal particles are located on a more carbon-rich surface. This supports a structural model in which the platinum metal particles are epitaxially grown on the (0001) basal surface plane of carbon graphite.

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“…From the perspective of supporting metal-containing species on CNFs, as is the case in their application as catalyst supports, functionalization of the nanofibres is in some cases a prerequisite. Through treatment with strong oxidizing media, oxygenated groups can be introduced onto the surface of CNF [5][6][7]. The number and type of these oxygen-containing moieties is highly dependent on the method of preparation.…”

Section: Introductionmentioning

confidence: 99%

Combined XPS and TPD study of oxygen-functionalized carbon nanofibers grown on sintered metal fibers

Rosenthal

Ruta

Schlögl

et al. 2010

Carbon

193

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A B S T R A C TA composite material consisting of carbon nanofibers (CNFs) grown on sintered metal fiber filters was modified by H 2 O 2 or plasma-generated O 3 . Coupling temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) techniques in the same UHV apparatus allowed the direct correlation of the nature of the created O-functional groups and their evolution as CO and CO 2 upon heating. The two oxidative treatments yielded different distributions of O-containing groups. The relative contribution of oxidized carbon was very low in the C1s region, hence the functional groups were more robustly analyzed through the O1s region. The comparison of the released oxygen by integration of the TPD CO, CO 2 and H 2 O spectra with the intensity loss of the XPS O1s spectra showed good agreement. In order to fit the data adequately, the set of O1s spectra was deconvoluted in at least four peaks for the differently activated samples. Finally, it was shown that functional groups formed by H 2 O 2 -treatment (mostly non-phenolic OH groups) are more thermally stable than those formed by O 3 -treatment. The latter treatment increases the concentration of carboxylic functionalities, which decompose at temperatures < 800 K;O 3 -activated CNFs should therefore show a more pronounced acidic behavior.

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The influence of oxidation on the texture and the number of oxygen-containing surface groups of carbon nanofibers

Cited by 351 publications

References 23 publications

Preparation of Carbon Nanofiber Supported Platinum and Ruthenium Catalysts: Comparison of Ion Adsorption and Homogeneous Deposition Precipitation

Preparation of Carbon Nanofiber Supported Platinum and Ruthenium Catalysts: Comparison of Ion Adsorption and Homogeneous Deposition Precipitation

Metal Particle Size and Structure of the Metal−Support Interface of Carbon-Supported Platinum Catalysts as Determined with EXAFS Spectroscopy

Combined XPS and TPD study of oxygen-functionalized carbon nanofibers grown on sintered metal fibers

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