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... D113 is a kind of weak acidic cation ex- change resin with macro-pores. Fe 2þ is exchanged into the acrylic chain of the resin and it works as graphitization cata- lyst. In the heating process the resin is carbonized first, then graphitized at 1100 C. In this work we pyrolyzed ion- exchange resin to get graphene and doped it with nitrogen. Fig. 2 presents the typical transmission electron microscopy (TEM) image of the undoped (Fig. 2a) and doped (Fig. 2b) gra- phene. No obvious difference is observed between doped and undoped graphene. The layer number of graphene can be directly observed by HRTEM in Fig. 2c and d. A thin graphene nanostructure with 8e10 layers can be observed ...
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... exchanged into the acrylic chain of the resin and it works as graphitization cata- lyst. In the heating process the resin is carbonized first, then graphitized at 1100 C. In this work we pyrolyzed ion- exchange resin to get graphene and doped it with nitrogen. Fig. 2 presents the typical transmission electron microscopy (TEM) image of the undoped (Fig. 2a) and doped (Fig. 2b) gra- phene. No obvious difference is observed between doped and undoped graphene. The layer number of graphene can be directly observed by HRTEM in Fig. 2c and d. A thin graphene nanostructure with 8e10 layers can be observed and the interlayer spacing is about 0.34 nm, which corresponds to the (002) distance of a graphitic carbon ...
Context 3
... work we pyrolyzed ion- exchange resin to get graphene and doped it with nitrogen. Fig. 2 presents the typical transmission electron microscopy (TEM) image of the undoped (Fig. 2a) and doped (Fig. 2b) gra- phene. No obvious difference is observed between doped and undoped graphene. The layer number of graphene can be directly observed by HRTEM in Fig. 2c and d. A thin graphene nanostructure with 8e10 layers can be observed and the interlayer spacing is about 0.34 nm, which corresponds to the (002) distance of a graphitic carbon lattice. The result is in well consistent with X-ray diffraction (XRD) ...
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Citations
... Figure 9 shows the comparison of the XRD patterns of N1-GP, N2-GP, N3-GP, N4-GP, N-GOP and N3-GPM. C(002) diffraction peaks correspond to multilayer graphene with a d-spacing of 3.36 Å. 82 (Figure 9). N3-GP, N4-GP, N-GOP and N3-GPM relatively high intensity and broad diffraction peak were observed. ...
In this study, symmetric supercapacitors in the form of coin cells were produced by using N-doped graphene powders as electrode components. Nitrogen-doped graphene powders were prepared by Yucel's Method with cyclic voltammetry at different potential ranges for selective modification of the powders with functional groups. Electrochemical, spectroscopic, and microscopic characterizations of N-doped graphene powders were carried out. The formation of graphene layers was supported by scanning electron microscopy and Raman analysis. Functional groups formed on the surfaces of N-doped graphene powders were determined by X-ray photoelectron spectroscopy. Specific capacitances of symmetric supercapacitors prepared with N-doped graphene powders were determined by cyclic charge-discharge tests. The highest specific capacitance, energy and power values were determined as 235.3 F.g−1, 158.2 Wh.kg−1 and 1760 W.kg−1, respectively.
... In recent years, heteroatom-doped graphene has become an alternative to platinum-based materials owing to the heteroatoms' improvement of electrochemi- www.nature.com/scientificreports/ cal properties 47,48 . In this case, graphene structures served as a matrix for the introduction of nitrogen, using the natural substrate Chlorella vurgalis as the source. ...
The synthesis of metal-free but electrochemically active electrode materials, which could be an important contributor to environmental protection, is the key motivation for this research approach. The progress of graphene material science in recent decades has contributed to the further development of nanotechnology and material engineering. Due to the unique properties of graphene materials, they have found many practical applications: among others, as catalysts in metal-air batteries, supercapacitors, or fuel cells. In order to create an economical and efficient material for energy production and storage applications, researchers focused on the introduction of additional heteroatoms to the graphene structure. As solutions for functionalizing pristine graphene structures are very difficult to implement, this article presents a facile method of preparing nitrogen-doped graphene foam in a microwave reactor. The influence of solvent type and microwave reactor holding time was investigated. To characterize the elemental content and structural properties of the obtained N-doped graphene materials, methods such as elemental analysis, high-resolution transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy were used. Electrochemical activity in ORR of the obtained materials was tested using cyclic voltamperometry (CV) and linear sweep voltamperometry (LSV). The tests proved the materials’ high activity towards ORR, with the number of electrons reaching 3.46 for tested non-Pt materials, while the analogous value for the C-Pt (20 wt% loading) reference was 4.
... The limiting current density increases with rotation rate, suggesting the kinetic limiting behavior of the ORR [43]. The onset potential of N-CNO was − 0.16 V which is lower than the onset potential for nitrogen-doped CNTs [68] and nitrogen-doped CNO [29,30], while the value is comparable to the onset potential of nitrogen-doped graphene [69] and nitrogen-doped mesoporous carbon [70]. The limiting current density of N-CNO was higher or comparable to reported values for other metalfree nitrogen-doped carbon catalysts [3,25,58,71]. ...
Growing environmental and economical concern necessitates novel materials with inherent electrochemical activity in as-prepared. Herein, we report, the electrochemical reactivity of the nitrogen-doped carbon nano-onions (N-CNO) prepared by a simple flame pyrolysis method. The as-obtained N-CNO has high N-content (4 at.%) and a large Brunauer-Emmett-Teller surface area (842.3 m² g⁻¹). The as-prepared N-CNO were probed as a cathode material for the oxygen reduction reaction (ORR) and as an electrocatalyst for sensitive nitrite (NO2−\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\mathrm{NO}}_2^{-} $$\end{document}) determination. The results demonstrate that, compared to N-CNT, as-prepared N-CNO exhibit a significantly enhanced ORR activity in alkaline medium and long-term stability with negligible change in activity. The N-CNO-based electrochemical nitrite sensor exhibits nitrite oxidation with two linear ranges 0.5 to 10 μM (R = 0.996) and 10 to 1000 μM (R = 0.978) with a sensitivity of 811.22 and 400.51 μA mM⁻¹ cm⁻², respectively. The detection limit (LOD) was 0.3 μM. The relative standard deviation (RSD) for eight replicate determinations was found to be 2.53%. The values of observed analytical parameters (linear range, sensitivity, and LOD) are comparable or superior to previously reported carbon-based NO2−\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\mathrm{NO}}_2^{-} $$\end{document} sensors.
Graphical AbstractNitrogen-Doped Carbon Nano-Onions as Metal-Free Electrocatalyst
... Figure 4a Figure 4c shows the high-resolution C1s spectrum of NCNCs. The C1s peak of N-doped graphene can be fitted into several spectral peaks, that is, C-C at 284.6 eV, C-O at 286.5 eV, C=O at 287.2 eV and O-C=O at 289.8 eV, respectively, which is similar to the previous reports [53,54]. Notably, a special peak located at 285.8 eV should be assigned to sp2 C atoms bonded with N, which further proves the doping effect of nitrogen. ...
Microwave plasma chemical vapor deposition (MPCVD) technique was successfully applied to fabricate Nitrogen-doped carbon nanocages (NCNCs) with doping content of 2.94 at.%. The NCNCs treated by HNO3 were characterized by TEM, XPS and Raman technique respectively. The rotating disk electrode voltammetry was used to estimate the oxygen reduction reaction (ORR) performance of nanocages in O2-saturated 0.1 M KOH electrolyte. Our results show that NCNCs possess not only electrocatalytic property comparable to those of commercial Pt/C catalyst, but also higher resistance to methanol crossover and better long-term stability than those of Pt/C. Therefore, NCNCs can be regarded as a very prominent alternative for Pt catalyst in ORR area.
... On the other hand, the Raman spectra of 0.4Ag@Ag 2 O/RGO 400 , 4Ag@Ag 2 O/RGO 250 , 4Ag@Ag 2 O/RGO 400 and 8.5Ag@Ag 2 O/RGO 250 nanocomposites show bands at 1354, 1355, 1352 and 1357 cm −1 , respectively, (due to D bands vibration) and 1589, 1597, 1589 and 1589 cm −1, respectively, related to G band [40]. They show also the 2D band with relative low intensity and high broadening ranged from 2825 cm −1 to 2956 cm −1 with the similar shape and position. ...
[email protected] 2 O/RGO nanocomposites with different loads of Ag (0.4%–8.5%) were synthesized using a simple deposition method in the presence of a triblock copolymer template at different annealing temperatures (250 °C and 400 °C). All samples were characterized with various techniques such as XRD, FTIR, Raman, TEM-SAED, N 2 sorptiometry and UV-Vis diffuse reflectance. The supercapacitor performance of the samples was measured. Besides, the catalytic performances of the samples towards 4-nitrophenol (4-NP) reduction were tested under dark conditions. The results revealed the well dispersion of Ag and Ag 2 O moieties on RGO with crystallite size in the range of 17–34 nm. The nanocomposite [email protected] 2 O/RGO annealed at 400 °C exhibited the highest reduction rate constant for 4-NP reduction (0.01 s ⁻¹ ). In addition, this composite has shown the highest specific capacitance of 312 F g ⁻¹ at scan rate of 20 mV s ⁻¹ and 119 F g ⁻¹ at a current density of 11 mA g ⁻¹ .
... Four nitrogen functionalities are indexed: pyridinic-N at 398.4 eV, pyrrolic-N at 399.5 eV, graphitic-N at 401.0 eV, and valley-N at 402.1 eV, which are labeled as N1 to N4 successively. It has been reported that N1, N3, and N4 contribute to the ORR active sites [31,32]. There are two sources of nitrogen in this work. ...
A non-noble metal Fe/N/C catalyst is prepared by pyrolyzing the ball-milled mixture of graphitized carbon ribbon, iron precursor, and nitrogen precursor in ammonia. The Fe/N/C catalyst shows high ORR activity in alkaline solution, together with much improved stability compared with Pt/C catalyst. In the catalyst, FeN particles are covered by graphitic carbon layers. The activity is proposed to originate from the FeN and Fe/N/C sites. The stability is explained by the protecting effect of the carbon layers surrounding the FeN particles. The ORR mechanism on the Fe/N/C catalyst is proposed to be similar with Pt/C catalyst based on the Tafel plots. The Fe/N/C catalyst shows great potential in ORR in alkaline solution, while the performance in acid still needs improvement.
... Beyond that, the graphitic N was reported to play a crucial role in oxygen reduction reaction, and pyridinic N and pyrrolic N can serve as metal coordination sites due to their lone-pair electrons [36]. Ouyang et al. [37] explored the active sites of nitrogen-doped graphene as catalysts for oxygen reduction reaction. The valley-N is certificated to play an important effect on ORR. ...
... However, their properties can be tailored by introducing dopants [19,21,22], generating defects [23] and by supporting them on transition metals [24][25][26]. Nitrogen doped graphene, for instance, has been shown to catalyze the electrochemical reduction of oxygen to water and the oxygen reduction reaction, (ORR) [22,[27][28][29][30][31][32][33][34]. ...
Although large efforts have been dedicated to studying two-dimensional materials for catalysis, a rationalization of the associated trends in their intrinsic activity has so far been elusive. In the present work we employ density functional theory to examine a variety of two-dimensional materials, including, carbon based materials, hexagonal boron nitride (h-BN), transition metal dichalcogenides (e.g. MoS2, MoSe2) and layered oxides, to give an overview of the trends in adsorption energies. By examining key reaction intermediates relevant to the oxygen reduction, and oxygen evolution reactions we find that binding energies largely follow the linear scaling relationships observed for pure metals. This observation is very important as it suggests that the same simplifying assumptions made to correlate descriptors with reaction rates in transition metal catalysts are also valid for the studied two-dimensional materials. By means of these scaling relations, for each reaction we also identify several promising candidates that are predicted to exhibit a comparable activity to the state-of-the-art catalysts.
Graphical Abstract
Scaling relationship for the chemisorption energies of OH* and OOH* on various 2D materials. Open image in new window
... Pyridinic-N and/or graphitic-N are believed to be active sites in ORR [12]. There is still dispute on whether the total nitrogen content is directly related with the activity of the oxygen reduction reaction [13,14]. ...
Nitrogen doped graphitic carbon ribbons are prepared by simultaneously graphitization and nitrogen doping of nano crystalline cellulose at high temperature. Ferrous salt works as catalyst for graphitization, without which amorphous carbon is resulted. The graphitic carbon ribbons and amorphous carbon are compared in detail in morphology, crystalline structure, defects, nitrogen groups and ORR activity by means of SEM, TEM, Raman, XRD, XPS and electrochemical characterizations. It is found the nitrogen doped graphitic carbon ribbons has comparable ORR activity with Pt/C catalyst in alkaline medium, which is much better than nitrogen doped amorphous carbon. The improved ORR activity is ascribed to the nitrogen group introduced by NH3 treatment of graphitic carbon. The as prepared material can work as efficient non noble metal catalyst for the oxygen reduction reaction.
... X-ray photoelectron spectroscopy (XPS) has for decades been one of the most widely used techniques for analyzing the quantity and bonding states in carbon-nitride compounds, in particular hard carbon-nitride films for wear-protective applications, such as a top coat on magnetic recording media [1][2][3][4][5][6][7][8][9]. More recently, XPS has been applied to analyzing nitrogen doping states in carbon nanotubes and graphene, primarily for understanding how to tailor their electronic properties [11][12][13][14][15][16][17]. Interpretation of the spectra, however, have proven to be quite challenging due to the many possible bonding configurations of N and C, combined with the inevitable interaction with oxygen and hydrogen on the film surface. ...
... With few exceptions, the N1s XPS peak consists of two major components, and often one to three smaller components, depending on the structure. There is a wide consensus that a major peak component in the 400.5-401 eV binding energy range corresponds to "graphitic" N, i.e., N substituted in a graphite layer [2][3][4][5][6][7][8][9][10][11][12][13][14]17,[22][23][24]. The interpretation of the other main component, typically found in the 398-398.5 eV range, has been more debated. ...
... There are three common assignments of the N1 peak component in the 399-400 eV range; (1) pyrrolic N [11,12,17,[22][23][24], (2) amino N ( NH 2 ) [12,31], and (3) nitriles ( C N) [4,7,9]. As mentioned previously, there is discrepancy in the literature on the definition of "pyrrolic" N. Here, we refer to any nitrogen bonded to two sp 2 carbons and a terminating hydrogen. ...
We report on angular-resolved x-ray photoelectron spectroscopy (XPS) studies of magnetron sputtered CN x thin films, first in situ (without air exposure), then after air exposure (for time periods ranging from minutes to several years), and finally after Ar ion etching using ion energies ranging from 500 eV to 4 keV. The as-deposited films typically exhibit two strong N1s peaks corresponding to pyridine-like, and graphite-like, at ∼398.2 eV and ∼400.7 eV, respectively. Comparison between in situ and air-exposed samples suggests that the peak component at ∼402–403 eV is due only to quaternary nitrogen and not oxidized nitrogen. Furthermore, peak components in the ∼399–400 eV range cannot only be ascribed to nitriles or pyrrolic nitrogen as is commonly done. We propose that it can also be due to a polarization shift in pyridinic N, induced by surface water or hydroxides. Argon ion etching readily removes surface oxygen, but results also in a strong preferential sputtering of nitrogen and can cause amorphization of the film surface. The best methods for evaluating and interpreting the CN x film structure and composition with ex-situ XPS are discussed.
