Properties of Carbon-Supported Platinum Catalysts: Role of Carbon Surface Sites

Fraga, Marco A.; Jordão, Elizabete; Mendes, Mário J. G. C.; Freitas, M.M.A.; Faria, Joaquim L.; Figueiredo, José L.

doi:10.1006/jcat.2002.3637

Cited by 215 publications

(99 citation statements)

References 35 publications

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“…These groups can decompose and being removed due to e.g. hydrogen spillover during reduction [22]. The substantial removal of oxygen surface groups for CNT is ascribed to the fact that this material has the highest concentration of oxygen surface groups present after oxidation of this material.…”

Section: Resultsmentioning

confidence: 99%

“…It is calculated that for this peak the theoretical H 2 /Pt ratio is around 6, which is above the expected value of 1. This is probably the result of the formation of other gases during the reduction/anion decomposition such as nitrogen oxides, ammonia, CO and CO 2 (the latter two gases originate from support gasification [22,23]), which will affect the TCD signal making quantitative statements obsolete.…”

Section: Resultsmentioning

confidence: 99%

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Reducibility of Platinum Supported on Nanostructured Carbons

et al. 2009

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The nanostructure of graphite like carbon, i.e. carbon nanofibers (CNF), carbon nanotubes (CNT) and carbon nanoplatelets (CNP), displayed a significant influence on the reducibility of platinum deposited on these carbons. The onset temperature for reduction increased from 461 K for Pt/CNF to 466 K for Pt/CNP and 487 K for Pt/CNT. The retarded reduction for Pt/CNT was related to the higher amount of acidic oxygen surface groups on this support resulting in a strong stabilization of the cationic platinum species. A higher reduction temperature for that sample increased the amount of metallic platinum, however the platinum particle size was larger (2-11 nm) compared to that of Pt/CNF and Pt/CNP (both 1-3 nm). The orientation of the graphene sheets had a significant influence on the selectivity for cinnamaldehyde hydrogenation: Pt/CNP resulted in a higher selectivity towards cinnamyl alcohol compared to Pt/CNF.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Reducibility of Platinum Supported on Nanostructured Carbons

et al. 2009

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“…The introduction of heteroatoms (N, O, P, and S) has been reported to confer higher hydrophilicity, enhanced metal-support interactions, and additional acidic or basic sites [23][24][25][26][27][28][29][30][31][32]. Obviously, the distribution, the amount, the location, and the specific binding forms of the heteroatoms on the surface strictly depend on the nature of the carbonaceous substrate.…”

Section: Introductionmentioning

confidence: 99%

Controlling the Incorporation of Phosphorus Functionalities on Carbon Nanofibers: Effects on the Catalytic Performance of Fructose Dehydration

Campisi

Trujillo

Motta

et al. 2018

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Phosphorylated carbons have been reported to be effective catalysts in dehydration reactions for biomass valorization. The amount and the nature of P groups are a key parameter affecting the catalytic performances of functionalized materials. Herein, we investigate the role of structural and surface properties of carbon-based materials, specifically carbon nanofibers, in determining the amount of P-functionalities. In order to incorporate P groups on carbon surfaces, various carbon nanofibers (CNFs) with different graphitization degrees have been functionalized through treatment with a H 3 PO 4 -HNO 3 mixture at 150 • C. The pristine materials, as well as the functionalization protocol, were properly selected to achieve an effective functionalization without drastically altering the morphology of the samples. Surface and structural properties of the synthesized functionalized materials have been investigated by means of transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The catalytic behavior of phosphorylated carbon nanofibers has been evaluated in the selective dehydration of fructose to hydroxymethylfurfural (HMF) to elucidate structure-activity relationships.

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“…The concentration and the nature of different functional groups are known to depend on the AC pretreatment by acids and bases and can be regulated by thermal treatment in different atmospheres. The influence of AC surface functional groups on the dispersion of transition metals on the catalyst surface was discussed earlier for Pt and Pd [11,[24][25][26], as well as for the Au/AC catalysts [27], but the cation exchange with protons of surface groups has not been investigated during the preparation of highly dispersed gold on activated carbon.…”

Section: Introductionmentioning

confidence: 99%

Highly dispersed gold on activated carbon fibers for low-temperature CO oxidation

Bulushev

Yuranov

Suvorova

et al. 2004

Journal of Catalysis

204

132

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Gold nanoparticles of 2-5 nm supported on woven fabrics of activated carbon fibers (ACF) were effective during CO oxidation at room temperature. To obtain a high metal dispersion, Au was deposited on ACF from aqueous solution of ethylenediamine complex [Au(en) 2 ]Cl 3 via ion exchange with protons of surface functional groups. The temperature-programmed decomposition method showed the presence of two main types of functional groups on the ACF surface: the first type was associated with carboxylic groups easily decomposing to CO 2 and the second one corresponded to more stable phenolic groups decomposing to CO. The concentration and the nature of surface functional groups was controlled using HNO 3 pretreatment followed by either calcination in He (300-1273 K) or by iron oxide deposition. The phenolic groups are able to attach Au 3+ ions, leading to the formation of small Au nanoparticles (< 5 nm) after reduction by H 2 . This was confirmed by high-resolution electron microscopy combined with X-ray energy-dispersive analysis. The catalyst with high Au dispersion demonstrated high activity in CO oxidation. The surface carboxylic groups decomposed during interaction with [Au(en) 2 ]Cl 3 solution and reduced Au 3+ to Au 0 , resulting in the formation of bigger (> 9 nm) Au agglomerates after reduction by H 2 . These catalysts demonstrated lower activity as compared to the ones containing mostly small Au nanoparticles. Complete removal of surface functional groups rendered an inert support that would not interact with the Au precursor. The oxidation state of gold in the Au/ACF catalysts was controlled by X-ray photoelectron spectroscopy before and after the reduction in H 2 . The high-temperature reduction in H 2 (673-773 K) was necessary to activate the catalyst, indicating that metallic gold nanoparticles are active during catalytic CO oxidation.  2004 Elsevier Inc. All rights reserved.

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Properties of Carbon-Supported Platinum Catalysts: Role of Carbon Surface Sites

Cited by 215 publications

References 35 publications

Reducibility of Platinum Supported on Nanostructured Carbons

Reducibility of Platinum Supported on Nanostructured Carbons

Controlling the Incorporation of Phosphorus Functionalities on Carbon Nanofibers: Effects on the Catalytic Performance of Fructose Dehydration

Highly dispersed gold on activated carbon fibers for low-temperature CO oxidation

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