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1.
Materials (Basel) ; 15(3)2022 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-35160764

RESUMO

A simple method for the mechanochemical synthesis of an effective metal-free electrocatalyst for the oxygen reduction reaction was demonstrated. A nitrogen-doped carbon material was obtained by grinding a mixture of graphene oxide and melamine in a planetary ball mill. The resulting material was characterized by XPS, EPR, and Raman and IR spectroscopy. The nitrogen concentration on the N-bmGO surface was 5.5 at.%. The nitrogen-enriched graphene material (NbmGO has half-wave potential of -0.175/-0.09 V and was shown to possess high activity as an electrocatalyst for oxygen reduction reaction. The electrocatalytic activity of NbmGO can be associated with a high concentration of active sites for the adsorption of oxygen molecules on its surface. The high current retention (93% for 12 h) after continuous polarization demonstrates the excellent long-term stability of NbmGO.

2.
Langmuir ; 37(33): 10233-10240, 2021 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-34387499

RESUMO

An improved procedure for the preparation of aerogel granules of polytetrafluoroethylene-graphene oxide (PTFE-GO) with a composition of 50:50 (in wt %) and a specific density of 35 ± 2 mg/cm3 is described. The technique practically excludes the granule cracking. The specific density of the pellets after reduction using hydrazine vapor and annealing at 370 °C decreased to 29 ± 2 mg/cm3. The PTFE-reduced GO (rGO) pellets obtained were tested as a recyclable sorbent for isopropyl alcohol (IPA) in sorption/combustion cycles. It has been shown that the aerogel sorption capacity for IPA increases from 35.6 to 39.3 g/g as a result of alcohol burning off. During the combustion of IPA, the temperature of an individual pellet can exceed 300 °C. When several contingent pellets are burned, the temperature of their heating increases. The fine-pored structure of the near-surface layer of the granule is destroyed during the alcohol burning, the internal structure with larger pores is exposed, and the relative proportion of PTFE on the surface of the granules decreases. It was also shown that the specific surface area of PTFE-rGO increases from 26 to 49 m2/g during cycling.

3.
Nanomaterials (Basel) ; 11(5)2021 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-34067894

RESUMO

The alkaline activation of a carbonized graphene oxide/dextrin mixture yielded a carbon-based nanoscale material (AC-TR) with a unique highly porous structure. The BET-estimated specific surface area of the material is 3167 m2/g, which is higher than the specific surface area of a graphene layer. The material has a density of 0.34 g/cm3 and electrical resistivity of 0.25 Ω·cm and its properties were studied using the elemental analysis, transmission electron microscopy (TEM), electron diffraction (ED), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray induced Auger electron spectroscopy (XAES), and electron energy loss spectroscopy (EELS) in the plasmon excitation range. From these data, we derive an integral understanding of the structure of this material. The concentration of sp3 carbon atoms was found to be relatively low with an absolute value that depends on the measurement method. It was shown that there is no graphite-like (002) peak in the electron and X-ray diffraction pattern. The characteristic size of a sp2-domain in the basal plane estimated from the Raman spectra was 7 nm. It was also found that plasmon peaks in the EELS spectrum of AC-TR are downshifted compared to those of graphite.

4.
Materials (Basel) ; 14(2)2021 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-33435447

RESUMO

A graphene oxide aerogel (GOA) was formed inside a melamine sponge (MS) framework. After reduction with hydrazine at 60 °C, the electrical conductive nitrogen-enriched rGOA-MS composite material with a specific density of 20.1 mg/cm3 was used to fabricate an electrode, which proved to be a promising electrocatalyst for the oxygen reduction reaction. The rGOA-MS composite material was characterized by elemental analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. It was found that nitrogen in the material is presented by different types with the maximum concentration of pyrrole-like nitrogen. By using Raman scattering it was established that the rGOA component of the material is graphene-like carbon with an average size of the sp2-domains of 5.7 nm. This explains a quite high conductivity of the composite obtained.

5.
Langmuir ; 36(30): 8680-8686, 2020 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-32631066

RESUMO

A mixture of water suspensions of graphene oxide (GO) and polytetrafluoroethylene (PTFE) was used to make the films GO-PTFE (50:50). They became conductive (2.0-2.8 S/cm) while maintaining flexibility after reduction with hydrazine and subsequent annealing at 370 °C. The structure and morphology of the reduced films (rGO-PTFE) are examined in detail by means of a number of techniques such as scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, Raman, and contact angle wetting. The results of the films tested as current collectors in a metal-free supercapacitor with electrodes from microwave exfoliated GO and an acid (1 M H2SO4) electrolyte are presented.

6.
ACS Appl Mater Interfaces ; 11(35): 32517-32522, 2019 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-31408314

RESUMO

Polytetrafluoroethylene-based aerogel was synthesized for the first time. Graphene oxide was used as a binder. After reduction with hydrazine and annealing at 370 °C, the aerogel with a density of 29 ± 2 mg/cm3 became superhydrophobic. The aerogel was characterized by IR spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. The sorption capacity of the aerogel for seven solvents and its sorption recyclability for hexane were measured.

7.
J Phys Chem A ; 110(27): 8528-34, 2006 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-16821837

RESUMO

Products of the reaction of C(60) with H(2) gas have been monitored by high-resolution atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry (APPI FT-ICR MS), X-ray diffraction, and IR spectroscopy as a function of hydrogenation period. Samples were synthesized at 673 K and 120 bar hydrogen pressure for hydrogenation periods between 300 and 5000 min, resulting in the formation of hydrofullerene mixtures with hydrogen content ranging from 1.6 to 5.3 wt %. Highly reduced C(60)H(x) (x > 36-40) and products of their fragmentation were identified in these samples by APPI FT-ICR MS. A sharp change in structure was observed for samples with at least 5.0 wt % of hydrogen. Low-mass (300-500 Da) hydrogenation products not observed by prior field desorption (FD) FT-ICR MS were detected by APPI FT-ICR MS and their elemental compositions obtained for the first time. Synthetic and analytical fragmentation pathways are discussed.

8.
J Phys Chem B ; 109(26): 12742-7, 2005 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-16852579

RESUMO

Complex solid hydrofulleride mixtures were synthesized by prolonged hydrogenation of C(60) at 120 bar hydrogen pressure, 673 K temperature, and different reaction periods. The high degree of hydrogenation was confirmed by infrared spectroscopy and X-ray diffraction. The identity of hydrogenation products was determined by high-resolution field desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry. Despite partial gas-phase fragmentation of hydrofullerene ions during mass analysis, the data suggest that the synthesized mixtures consist of mostly C(58-60)H(x) hydrofullerenes. Increasing the duration of hydrogenation results in synthesis of C(59)H(x) and C(58)H(x) as major products. Possible hydrofullerene fragmentation pathways during both material synthesis and mass spectrometric analysis are discussed. Gas-phase fragmentation in the mass spectrometer arises from hydrofullerene ions C(60)H(x)(+) with x > 40 and C(59)H(44)(+) with drastically decreased molecular stability relative to the known C(60)H(36).

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