638 research outputs found
Microporous sulfur-doped carbon from thienyl-based polymer network precursors
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugĂ€nglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Porous sulfur-doped carbon was synthesised by using a thienyl-based polymer network as a precursor. The sulfur amount varies from 5â23 m% while the materials show microporosity with BET surface areas of up to 711 m2 gâ1.DFG, EXC 314, Unifying Concepts in Catalysi
Synthesis of mesoporous composite materials of nitrogen-doped carbon and silica using a reactive surfactant approach
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugĂ€nglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Mesoporous composite materials of nitrogen-doped carbon and silica were synthesised in a one-step-process applying a soft templating procedure. The template used in the solâgel synthesis of the silica is a cationic surfactant with distinct reactivity to form nitrogen-doped graphitic carbon upon heating. This reactivity is derived from the combination of the dicyanamide anion with a nitrogen-containing pyridinium cation, as it is known from ionic liquids used as nitrogen-doped carbon precursors. Thus applying this surfactant in a conventional solâgel synthesis yields a silica gel doped with a precursor for N-doped carbon. By subsequent annealing mesoporous composite materials of silica and nitrogen-doped carbon are obtained
Nitrogen- and phosphorus-co-doped carbons with tunable enhanced surface areas promoted by the doping additives
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugÀnglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.1-Butyl-3-methyl-pyridinium-dicyanamide (BMP-dca) is carbonised with tetra-alkyl-phosphonium-bromide additives yielding nitrogen- and phosphorus-co-doped carbons with enhanced BET surface areas promoted by the additives.DFG, EXC 314, Unifying Concepts in Catalysi
Nitrogen-doped coatings on carbon nanotubes and their stabilizing effect on Pt nanoparticles
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugĂ€nglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.A homogeneous coating of nitrogen-doped carbon on carbon nanotubes is performed using ionic liquids. The N-doped material is employed as a support for nanoparticles. Electrochemical degradation behavior is monitored in situ and compared to an unmodified material. The strongly enhanced stability is explained on the basis of a Ptânitrogen interaction.DFG, EXC 314, Unifying Concepts in Catalysi
Sulfur and nitrogen co-doped graphene for metal-free catalytic oxidation reactions
Sulfur and nitrogen co-doped reduced graphene oxide (rGO) is synthesized bya facile method and demonstrated remarkably enhanced activities in metal-free activation of peroxymonosulfate (PMS) for catalytic oxidation of phenol. Based on first-order kinetic model, SâN co-doped rGO (SNG) presents an apparent reaction rate constant of 0.043 ± 0.002 min -1 , which is 86.6, 22.8, 19.7, and 4.5-fold as high as that over graphene oxide (GO), rGO, S-doped rGO (S-rGO), and N-doped rGO(N-rGO), respectively. A variety of characterization techniques and density functional theory calculations are employed to investigate the synergistic effect of sulfur and nitrogen co-doping. Co-doping of rGO at an optimal sulfur loading can effectively break the inertness of carbon systems, activate the sp 2 -hybridized carbon lattice and facilitate the electron transfer from covalent graphene sheets for PMS activation. Moreover, both electron paramagnetic resonance (EPR) spectroscopy and classical quenching tests are employed to investigate the generation and evolution of reactive radicals on the SNG sample for phenol catalytic oxidation. This study presents anovel metal-free catalyst for green remediation of organic pollutants in water
Tuning the Catalytic Activity of Graphene Nanosheets for Oxygen Reduction Reaction via Size and Thickness Reduction
Currently, the fundamental factors that control the oxygen reduction reaction
(ORR) activity of graphene itself, in particular the dependence of the ORR
activity on the number of exposed edge sites remain elusive, mainly due to
limited synthesis routes of achieving small size graphene. In this work, the
synthesis of low oxygen content (< 2.5 +/-0.2 at %), few layer graphene
nanosheets with lateral dimensions smaller than a few hundred nm was achieved
using a combination of ionic liquid assisted grinding of high purity graphite
coupled with sequential centrifugation. We show for the first time, that the
graphene nanosheets possessing a plethora of edges exhibited considerably
higher electron transfer numbers compared to the thicker graphene
nanoplatelets. This enhanced ORR activity was accomplished by successfully
exploiting the plethora of edges of the nanosized graphene as well as the
efficient electron communication between the active edge sites and the
electrode substrate. The graphene nanosheets were characterized by an onset
potential of -0.13 V vs. Ag/AgCl and a current density of -3.85 mA/cm2 at -1 V,
which represent the best ORR performance ever achieved from an undoped carbon
based catalyst. This work demonstrates how low oxygen content nanosized
graphene synthesized by a simple route can considerably impact the ORR
catalytic activity and hence it is of significance in designing and optimizing
advanced metal-free ORR electrocatalysts.Comment: corresponding author: [email protected], ACS Applied
Materials and Interfaces 201
Biomass-derived three-dimensional porous N-doped carbonaceous aerogel for efficient supercapacitor electrodes
Functionalized carbonaceous materials with hierarchical structure and developed porosity are highly desired in energy storage and conversion fields. In this work, a facile and scalable hydrothermal methodology was established to synthesise three-dimensional (3D) N-doped carbonaceous aerogels using biomass-based starting materials and polypyrrole as N-source. The effect of different calcination temperatures on the structural properties, type and content of N-species and electrochemical performance of the 3D N-doped carbonaceous aerogels were uncovered. Thanks to the combinatorial effect of the appropriate N content and porous structure, the obtained samples exhibited excellent electrochemical performance, in particular, an outstanding specific capacitance of 281.0 F g-1 achieved on the sample calcined at 600 °C. This methodology offers a new fabrication strategy to prepare nanoscale carbonaceous materials with desirable morphology and hierarchical architecture of great potentials for the applications in energy fields
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