Beyond confinement effects in Fischer-Tropsch Co/CNT catalysts

Understanding the mechanism of iron‐catalyzed graphitization of biomass is an important step for the large‐scale synthesis of green graphene. Although iron is known to be the most active transition metal for the catalytic graphitization of cellulose‐derived biochar, the direct effect of the iron molecular structure on the formation of highly graphitic carbon remains elusive. Here, biochar was produced from pyrolysis of iron‐impregnated cellulose at three different temperatures (1000, 1400, and 1800 °C). X‐ray diffraction, X‐ray photoelectron spectroscopy, and magnetic measurements were used to probe changes in biochar nanostructure catalyzed by the inclusion of iron. An increase of pyrolysis temperature led to an increase in the iron particle size and the degree of iron reduction, as well as the formation of larger graphitic carbon crystallite sizes, and these two attributes of iron were seen to positively affect the biochar graphitization usually challenging under 2000 °C.

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“…Analysis was investigated using a monochromatized Al K α source on a ThermoScientific K α [30] . The X‐ray spot size varies from 30 to 400 μm.…”

Section: Methodsmentioning

confidence: 99%

Synthesis and Growth of Green Graphene from Biochar Revealed by Magnetic Properties of Iron Catalyst

et al. 2022

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“…According to the heteroatom doping, different types of surface groups have been reported to facilitate the H-spillover on Pd catalysts, such as N-quaternary atoms for N-doped materials [65] and quinone groups for O-doped ones. [67] Interestingly, it was also reported that water molecules, present as solvent during 4-NP reduction, significantly facilitate the H-spillover reaction on carbon supports by acting as shuttle/stabilizer for the Hspecies. [63,65,68] H-spillover should not occur on undoped CNTs because of the low concentration of surface oxygen groups.…”

Section: Chemcatchemmentioning

confidence: 99%

Multifunctional Catalytic Properties of Pd/CNT Catalysts for 4‐Nitrophenol Reduction

et al. 2022

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Carbon nanotubes are arousing real interest in catalysis, either as catalyst support or as catalyst itself. In this work, the influence of CNT doping (O, N, S) on the catalytic performance of CNT and Pd/CNT catalysts have been investigated in the reduction of 4-nitrophenol both under H 2 or using NaBH 4 as a hydride source. The morphology, composition, particle size and crystallinity of the materials were investigated by various techniques including HRTEM, STEM, XPS, Raman spectroscopy and XRD. Among the CNT carbocatalysts, only N-CNT is active for 4-nitrophenol reduction at room temperature, and only in the presence of NaBH 4 . As far as supported Pd catalysts are concerned, the nature of the support influences the Pd nanoparticle location (confinement), the Pd nanoparticles/Pd single atoms ratio and the extent of H-spillover, three catalyst features that directly affect the catalytic activity. The best combination of Pd nanoparticles/Pd single atoms ratio, H-spillover and confinement for 4-nitrophenol reduction using NaBH 4 , is found in Pd/O-CNT catalysts, while for reactions performed under H 2 , Pd/N-CNT presents the best combination.

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“…For this set of samples, we first confirmed that the nitrate metal precursor did not cause any reoxidation of the carbon surface during catalyst synthesis (Table S4). Such a reoxidation was observed for Co/CNT catalysts, albeit for much higher metal loadings . The combined XPS/UPS analysis of the Pd(NO 3 ) 2 /CNT precursor showed a rapid drop of the O/C ratio from 0.21 to 0.12 when heating the sample to 200 °C.…”

Section: Resultsmentioning

confidence: 99%

“…Such a reoxidation was observed for Co/CNT catalysts, albeit for much higher metal loadings. 64 The combined XPS/UPS analysis of the Pd(NO 3 ) 2 /CNT precursor showed a rapid drop of the O/C ratio from 0.21 to 0.12 when heating the sample to 200 °C. The latter is close to the O/C ratio of 0.11 obtained for the oxidized CNTs when defunctionalized at the same temperature.…”

Section: Theoretical Insights Intomentioning

confidence: 99%

Oxygen-Doped Carbon Supports Modulate the Hydrogenation Activity of Palladium Nanoparticles through Electronic Metal–Support Interactions

et al. 2022

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In heterogeneous catalysis, synergies between the metal active phase and oxide support can enhance the catalytic activity through electronic metal–support interactions (EMSI). Such effects are unexpected for conventional carbon supports, and carbon is often viewed as an inert scaffold in catalysis. Here, we demonstrate that carbons do present EMSI that alter the intrinsic rate of palladium atoms near the interface by 200-fold compared to atoms at the apex of 5 nm particles. We also show that oxygen-containing functional groups, which are ubiquitous on carbon surfaces, are responsible for these EMSI. Controlling the scaffold’s surface chemistry allowed us to tune its work function from 5.1 to 4.7 eV, the intensity of the charge redistribution at the metal–carbon interface, and the catalytic activity of the corresponding metal atoms. The proposed platform can be applied to fundamentally understand EMSI effects for reactions and carbonaceous supports beyond those studied in the present work.

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Beyond confinement effects in Fischer-Tropsch Co/CNT catalysts

Cited by 21 publications

References 101 publications

Synthesis and Growth of Green Graphene from Biochar Revealed by Magnetic Properties of Iron Catalyst

Synthesis and Growth of Green Graphene from Biochar Revealed by Magnetic Properties of Iron Catalyst

Multifunctional Catalytic Properties of Pd/CNT Catalysts for 4‐Nitrophenol Reduction

Oxygen-Doped Carbon Supports Modulate the Hydrogenation Activity of Palladium Nanoparticles through Electronic Metal–Support Interactions

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