Monitoring the thermally induced transition from sp3-hybridized into sp2-hybridized carbons

Schüpfer, Dominique; Badaczewski, Felix; Peilstöcker, Jan; Guerra-Castro, Juan Manuel; Shim, Hwirim; Firoozabadi, Saleh; Beyer, Andreas; Volz, Kerstin; Presser, Volker; Heiliger, Christian; Smarsly, Bernd M.; Klar, Peter J.

doi:10.1016/j.carbon.2020.09.063

Cited by 65 publications

(36 citation statements)

References 56 publications

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“…Both Raman spectra of Ru@ MCN and MCN present two prominent peaks at 1350 and 1585 cm −1 (Figure S4) corresponding to the D and G bands that are characteristic of disordered and sp2-hybridized graphitic carbons, respectively. 47 In both samples, the intensity of the D band is notably higher, corroborating the defective carbon matrix as indicated previously by XRD. Meanwhile, the intensity ratios between the D and G bands (I D /I G ) for both The electrochemical properties of Ru@MCN when employed as the oxygen-cathode catalyst were evaluated in the coin-type LOBs and compared to MCN and Super P. Figure 2a displays the initial discharge/charge curves of LOBs at a current density of 100 mA g −1 with a cut-off capacity of 500 mA h g −1 for all the three materials.…”

Section: Resultssupporting

confidence: 88%

“…The high-resolution Ru 3p spectrum confirms the presence of only one Ru 0 species, which is located at 463.2 and 485.5 eV, respectively, for spin orbitals of Ru 3p 1/2 and Ru 3p 3/2 , together with their satellites (Figure S3b). Both Raman spectra of Ru@MCN and MCN present two prominent peaks at 1350 and 1585 cm –1 (Figure S4) corresponding to the D and G bands that are characteristic of disordered and sp2-hybridized graphitic carbons, respectively . In both samples, the intensity of the D band is notably higher, corroborating the defective carbon matrix as indicated previously by XRD.…”

Section: Resultssupporting

confidence: 83%

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Ru-Embedded Highly Porous Carbon Nanocubes Derived from Metal–Organic Frameworks for Catalyzing Reversible Li₂O₂ Formation

et al. 2021

ACS Appl. Mater. Interfaces

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Rechargeable lithium–oxygen batteries (LOBs) have attracted increasing attention due to their high energy density but highly rely on the development of efficient oxygen catalysts for reversible Li2O2 deposition/decomposition. Herein, highly porous carbon nanocubes with a specific surface area up to 1600 m2 g–1 are synthesized and utilized to tightly anchor Ru nanoparticles for using as the oxygen-cathode catalyst in LOBs, achieving a low charge/discharge potential gap of only 0.75 V, a high total discharge capacity of 17,632 mA h g–1, and a superb cycling performance of 550 cycles at 1000 mA g–1. Comprehensive ex situ and operando characterizations unravel that the outstanding LOB performance is ascribed to the highly porous catalyst structure embedding rich active sites that synergistically function in reducing overpotentials, suppressing parasitic reactions, accommodating reaction products, and promoting mass and charge transportation.

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Section: Resultssupporting

confidence: 88%

Section: Resultssupporting

confidence: 83%

Ru-Embedded Highly Porous Carbon Nanocubes Derived from Metal–Organic Frameworks for Catalyzing Reversible Li₂O₂ Formation

et al. 2021

ACS Appl. Mater. Interfaces

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“…The process continues by formation of surface-graphitized NDs above 700 °C [ 9 ]. Next, when the temperature rises above 1000 °C, the external graphene patches start to merge and the defect density decreases [ 10 ]. Highly crystalline and low-defect OLCs are typically obtained at annealing temperatures higher than 1500 °C [ 11 ].…”

Section: Introductionmentioning

confidence: 99%

Laser-Induced Modification of Hydrogenated Detonation Nanodiamonds in Ethanol

et al. 2021

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Apart from the frequently used high-temperature annealing of detonation nanodiamonds (DNDs) in an inert environment, laser irradiation of DNDs in a liquid can be effectively used for onion-like carbon (OLC) formation. Here, we used fully de-aggregated hydrogenated DNDs (H-DNDs) dispersed in ethanol, which were irradiated for up to 60 min using a 532 nm NdYAG laser with an energy of 150 mJ in a pulse (5 J/cm2) at a pulse duration of 10 ns and a repetition rate of 10 Hz. We investigated the DND surface chemistry, zeta potential, and structure as a function of laser irradiation time. Infrared spectroscopy revealed a monotonical decrease in the C–Hx band intensities and an increase of the C–O and C=O features. Transmission electron microscopy (TEM) revealed the formation of OLC, as well as a gradual loss of nanoparticle character, with increasing irradiation time. Surprisingly, for samples irradiated up to 40 min, the typical and unchanged DND Raman spectrum was recovered after their annealing in air at 450 °C for 300 min. This finding indicates the inhomogeneous sp3 to sp2 carbon transformation during laser irradiation, as well as the insensitivity of DND Raman spectra to surface chemistry, size, and transient structural changes.

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“…However, our results show that the G bands in RGO sifted towards higher wavenumbers. Schüpfer et al observed similar behavior when studying the transition from sp 3 to sp 2 hybridization in heat-treated graphitic and non-graphitic carbon, with a G band close to 1600 cm −1 [33]. The ratio between the intensity of the D and G bands (I D /I G ) was also calculated since it is generally used to measure structural disorder.…”

Section: Resultsmentioning

confidence: 83%

Controlled Reduction of Graphene Oxide Using Sulfuric Acid

et al. 2020

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Sulfuric acid under different concentrations and with the addition of SO3 (fuming sulfuric acid) was studied as a reducing agent for the production of reduced graphene oxide (RGO). Three concentrations of sulfuric acid (1.5, 5, and 12 M), as well as 12 M with 30% SO3, were used. The reduction of graphene oxide increased with H2SO4 concentration as observed by Fourier-transformed infrared spectroscopy and X-ray photoelectron spectroscopy. It was observed that GO lost primarily epoxide functional groups from 40.4 to 9.7% and obtaining 69.8% carbon when using 12 M H2SO4, without leaving sulfur doping. Additionally, the appearance of hexagonal domain structures observed in transmission electron microscopy and analyzed by selected area electron diffraction patterns confirmed the improvement in graphitization. Although the addition of SO3 in H2SO4 improved the GO reduction with 74% carbon, as measured by XPS, the use of SO3 introduced sulfur doping of 1.3%. RGO produced with sulfuric acid was compared with a sample obtained via ultraviolet (UV) irradiation, a very common reduction route, by observing that the RGO produced with sulfuric acid had a higher C/O ratio than the material reduced by UV irradiation. This work showed that sulfuric acid can be used as a single-step reducing agent for RGO without sulfur contamination.

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Monitoring the thermally induced transition from sp3-hybridized into sp2-hybridized carbons

Cited by 65 publications

References 56 publications

Ru-Embedded Highly Porous Carbon Nanocubes Derived from Metal–Organic Frameworks for Catalyzing Reversible Li₂O₂ Formation

Ru-Embedded Highly Porous Carbon Nanocubes Derived from Metal–Organic Frameworks for Catalyzing Reversible Li₂O₂ Formation

Laser-Induced Modification of Hydrogenated Detonation Nanodiamonds in Ethanol

Controlled Reduction of Graphene Oxide Using Sulfuric Acid

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Monitoring the thermally induced transition from sp3-hybridized into sp2-hybridized carbons

Cited by 65 publications

References 56 publications

Ru-Embedded Highly Porous Carbon Nanocubes Derived from Metal–Organic Frameworks for Catalyzing Reversible Li2O2 Formation

Ru-Embedded Highly Porous Carbon Nanocubes Derived from Metal–Organic Frameworks for Catalyzing Reversible Li2O2 Formation

Laser-Induced Modification of Hydrogenated Detonation Nanodiamonds in Ethanol

Controlled Reduction of Graphene Oxide Using Sulfuric Acid

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Product

Resources

About

Ru-Embedded Highly Porous Carbon Nanocubes Derived from Metal–Organic Frameworks for Catalyzing Reversible Li₂O₂ Formation

Ru-Embedded Highly Porous Carbon Nanocubes Derived from Metal–Organic Frameworks for Catalyzing Reversible Li₂O₂ Formation