Nanoporous graphene by quantum dots removal from graphene and its conversion to a potential oxygen reduction electrocatalyst via nitrogen doping

Palaniselvam, Thangavelu; Valappil, Manila Ozhukil; Illathvalappil, Rajith; Kurungot, Sreekumar

doi:10.1039/c3ee43648a

Cited by 156 publications

(119 citation statements)

References 48 publications

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“…[217,249] This result has been confirmed by the theoretical results,s uggesting that oxygen adsorption on edge or defect spots is easier than that on the integrated basal plane. [250,251] Despite the above successes from experimental and simulation work, direct evidence that links the ORR activity obtained with these sites is still absent.…”

Section: Angewandte Chemiesupporting

confidence: 89%

Earth‐Abundant Nanomaterials for Oxygen Reduction

et al. 2015

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Replacing the rare and precious platinum (Pt) electrocatalysts with earth-abundant materials for promoting the oxygen reduction reaction (ORR) at the cathode of fuel cells is of great interest in developing high-performance sustainable energy devices. However, the challenging issues associated with non-Pt materials are still their low intrinsic catalytic activity, limited active sites, and the poor mass transport properties. Recent advances in material sciences and nanotechnology enable rational design of new earth-abundant materials with optimized composition and fine nanostructure, providing new opportunities for enhancing ORR performance at the molecular level. This Review highlights recent breakthroughs in engineering nanocatalysts based on the earth-abundant materials for boosting ORR.

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Section: Angewandte Chemiesupporting

confidence: 89%

Earth‐Abundant Nanomaterials for Oxygen Reduction

et al. 2015

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“…The diffraction peak at 2θ = 22.4° corresponds to a d spacing of 0.40 nm along the (002) direction, which is larger than that of graphite (0.334 nm). The larger d 002 spacing of our NGQDs can be attributed to the presence of the functional groups and nitrogen doping atoms enlarging the basal plane spacing, which is similar to those of NGQDs prepared by other methods [26,29,32]. The atomic force microscopy (AFM) image ( Figure 2D range from 0.5 to 1.5 nm ( Figure 2E), suggesting that most NGQDs consist of one to three graphene monolayers.…”

Section: Resultsmentioning

confidence: 49%

Ultrafast ammonia-driven, microwave-assisted synthesis of nitrogen-doped graphene quantum dots and their optical properties

et al. 2016

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Abstract:For the first time, a facile, ultrafast, ammoniadriven microwave-assisted synthesis of high-quality nitrogen-doped graphene quantum dots (NGQDs) at room temperature and atmospheric pressure is presented. This one-step method is very cheap, environment friendly, and suitable for large-scale production. The as-synthesized NGQDs consisting of one to three graphene monolayers exhibit highly crystalline quality with an average size of 5.3 nm. A new fluorescence (FL) emission peak at 390 nm is observed, which might be attributed to the doped nitrogen atoms into the GQDs. An interesting red-shift is observed by comparing the FL excitation spectra to the UV-visible absorption spectra. Based on the optical properties, the detailed Jablonski diagram representing the energy level structure of NGQDs is derived.

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“…[ 25,34 ] At the same time, pyrrole monomer was introduced into the holey-graphene hydrogel (HGH) for in situ polymerization to provide the N source and to prevent possible selfstacking of HGH. Finally, NHGH was converted into NHGM after shrinking and annealing.…”

Section: Wileyonlinelibrarycommentioning

confidence: 99%

High‐Density Monolith of N‐Doped Holey Graphene for Ultrahigh Volumetric Capacity of Li‐Ion Batteries

Wang

Cheng

et al. 2016

Advanced Energy Materials

167

132

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To solve the aforementioned problems, emerging graphene agglomerates with crumpled morphologies obtained by the stacking of graphene sheets seem to be promising for increasing the packing density and energy density in energystorage devices. [ 23,24 ] Unfortunately, they usually exhibit a rather low packing density, and consequently a relatively low volumetric capacity. Additionally, the closely stacked graphene agglomerate electrodes generally decrease the ion-accessible surface area and electrolyte ion diffusion, which inevitably compromises its lithium storage capacity. Thus, both a high density and porous structure should be taken into consideration when seeking a strategy for the synthesis of novel carbon-based LIB anodes.Recently, holey graphene, as a new class of graphene derivatives, has attracted extensive attention because of its high intrinsic electrical conductivity, open ion channels, and edge activity useful for applications in electrochemistry-related fi elds. [ 8,25 ] In our previous study, we have demonstrated a lightweight porous graphene foam as advanced electrode material for electrochemical processes (e.g., hydrogen evolution reaction, oxygen reduction reaction, ethanol oxidation reaction, and as electrochemical capacitor). [26][27][28][29][30] Herein, we report a N-doped holey-graphene monolith (NHGM) with a dense microstructure and high density of 1.1 g cm −3 . The holey structure in the individual graphene sheets could not only provide effi cient diffusion channels for Li ions and a highly conductive pathway for electrons, but also provided more edges on the sheet to enhance Li intercalation. [ 31,32 ] NHGM was obtained by conjugating N-containing holey-graphene sheets into a 3D hydrogel, followed by evaporation of the trapped water under vacuum at room temperature and an annealing treatment under Ar atmosphere. This highly compact but porous architecture with heteroatom doping is favorable for ion diffusion, Li ion storage, and maximizing the LIB properties; the NHGM had a volumetric capacity of 1052 mAh cm −3 , which is nearly three times that of commercial graphite anodes (370 mAh cm −3 ), [ 33 ] and exhibited competitive characteristics over the existing Si-based and carbon/sulfur hybrid electrode materials (see Table S1 in the Supporting Information). This makes our graphene-based electrode material an important step toward practical applications.To prepare the N-doped, high-density, holey-graphene monolith (NHGM), we fi rst produced the N-containing holeygraphene hydrogel (NHGH) by a one-pot hydrothermal process with simultaneous etching of nanopores in the graphene sheets and co-assembly of graphene and pyrrole to form a 3D hydrogel. During the hydrothermal process, a controlled amount of H 2 O 2

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Nanoporous graphene by quantum dots removal from graphene and its conversion to a potential oxygen reduction electrocatalyst via nitrogen doping

Cited by 156 publications

References 48 publications

Earth‐Abundant Nanomaterials for Oxygen Reduction

Earth‐Abundant Nanomaterials for Oxygen Reduction

Ultrafast ammonia-driven, microwave-assisted synthesis of nitrogen-doped graphene quantum dots and their optical properties

High‐Density Monolith of N‐Doped Holey Graphene for Ultrahigh Volumetric Capacity of Li‐Ion Batteries

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