• Composites Research
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• v.36 no.6
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• pp.408-415
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• 2023

The formation of bonding configurations such as pyridinic-N, pyrrolic-N, and graphitic-N by nitrogen doping plays a crucial role in imparting distinct physical properties to carbon nanomaterials. In this study, we propose a simple and cost-effective approach to regulate nitrogen dopant configurations in carbon nanotubes (CNTs) by mixing melamine as a dopant source. We employed three distinct mechanical mixing techniques, namely magnetic stirring, bath sonication and tip sonication. The higher the ratio of melamine to CNT, the higher the ratio of Pyrrolic-N, and when mixed through stirring, the highest ratio of Pyridinic-N was shown. The facile method proposed in this study, which can easily form various types of nitrogen dopants in carbon nanotubes, is expected to facilitate the application of nitrogen-doped carbon nanomaterials.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.214.1-214.1
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• 2011

In this work, the electrochemical properties of the surface treated multi-walled carbon nanotubes (MWNTs) are investigated for supercapacitors. Nitrogen- and oxygen functional groups containing MWNTs are prepared by nitrogen precursors and acidic treatment, respectively. The surface properties of the MWNTs are confirmed by X-ray photoelectron spectroscopy (XPS) and Zeta-potential measurements. The electrochemical properties of the MWNTs are investigated by cyclic voltammetry, impedance spectra, and charge-discharge cycling performance in 1 M $H_2SO_4$ at room temperature. As a result, these functionalized MWNTs lead to an increase in the specific capacitance as compared with the pristine MWNTs. It proposes that the pyridinic and pyridinic-N-oxides nitrogen species influence on the specific capacitance due to their positive charges, and thus an improved electron transfer at high current loads, since they are the most important functional groups affecting capacitive behaviors.

• Applied Chemistry for Engineering
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• v.34 no.4
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• pp.426-433
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• 2023

Capacitor performance was considered using coffee grounds-based activated carbon produced through oil extraction and KOH activation to increase the utilization of boiwaste. Oil extraction from coffee grounds was performed by solvent extraction using n-Hexane and isopropyl alcohol solvents. The AC_CG-Hexane/IPA produced by KOH activation after oil extraction increased the specific surface area by up to 16% and the average pore size by up to 2.54 nm compared to AC_CG produced only by KOH activation without oil extraction. In addition, the pyrrolic/pyridinic N functional group of the prepared activated carbon increased with the extraction of oil from coffee grounds. In the cyclic voltage-current method measurement experiment, the specific capacitance of AC_CG-Hexane/IPA at a voltage scanning speed of 10 mV/s is 133 F/g, which is 33% improved compared to the amorphous capacity of AC_CG (100 F/g). The results show improved electrochemical properties by improving the size and specific surface area of the mesopores of activated carbon by removing components from coffee grounds oil and synergistic effects by increasing electrical conductivity with pyrrolic/pyridinic N functional groups. In this study, the recycling method and application of coffee grounds, a bio-waste, is presented, and it is considered to be one of the efficient methods that can be utilized as an electrode material for high-performance supercapacitors.

• Advances in nano research
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• v.9 no.1
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• pp.25-32
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• 2020

In this work, we report the use of caffeine as an alternative source of nitrogen to successfully dope graphene (quaternary 400.6 eV and pyridinic at 398 eV according XPS), as well as the growth of silver nanowires (in-situ) in the surface of nitrogen doped graphene (NG) sheets. We used the improved graphene oxide method (IGO), chemical reduction of graphene oxide (GOx), and impregnation with caffeine as source of nitrogen for doping and subsequently, silver nanowires (NW) grow in the surface by the reduction of silver salts in the presence of NG, achieving a numerous of growth of NW in the graphene sheets. As supporting experimental evidence, the samples were analyzed using conventional characterization techniques: SEM-EDX, XRD, FT-IR, micro RAMAN, TEM, and XPS.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.647-647
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• 2013

We apply a density functional theory (DFT) and DFT-based non-equilibrium Green's function approach to study the structures, energetics and charge transport characteristics of nitrogen-doped graphene and graphene nanoribbons (GNRs) with additional doping of phosphorus or boron atoms. Considering graphitic, pyridinic, and porphrin-like N doping sites and increasing N-doping concentration, we analyze the structures of N-P and N-B doped graphene and particularly focus on how they affect the charge transport along the lateral direction. For the GNRs, we also consider the differences between defects formed at the edge and bulk regions. Implications of our findings in the context of electronic and energy device applications will be also discussed.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.129-139
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• 2018

The effects of N doping concentration and dopant moieties on the electrochemical properties of nanoporous graphene and their dependence on annealing temperature are investigated. Four types of N moieties - amide, amine, graphitic-N, and oxidized-N - are obtained, which transformed into pyridinic-N and pyrrolic-N upon annealing. The diffusion coefficient (D') of the ions in the electrode is the maximum at $400^{\circ}C$ because of a high level of N doping, whereas the second highest D0 value is obtained at $700^{\circ}C$ owing to a high level of reduction and N doping. The highest specific capacitance is obtained for the sample annealed at $400^{\circ}C$.

• Journal of the Korean Electrochemical Society
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• v.15 no.2
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• pp.90-94
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• 2012

We report nanostructure electrodes with $TiO_2$ as a core and carbon as a shell ($TiO_2$@C) for oxygen reduction in alkaline solution. The structure of core-shell electrodes is characterized by transmission electron microscopy, Raman spectroscopy, X-ray diffraction method, and X-ray photoelectron microscopy. The electrochemical properties of the $TiO_2$@C electrodes are characterized using a potentiostat and compared with those of carbon supported Pt catalyst. In particular, the core-shell electrode with dominant pyridinic-N component exhibits an imporved electrocatalytic activity for oxygen reduction reaction in alkaline solution.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.192.2-192.2
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• 2014

Among various dopant candidates, nitrogen (N) atoms are considered as the most effective dopants to improve the diverse properties of graphene. Unfortunately, recent experimental and theoretical studies have revealed that different N-doped graphene (NGR) conformations can result in both p- and n-type characters depending on the bonding nature of N atoms (substitutional, pyridinic, pyrrolic, and nitrilic). To overcome this obstacle in achieving reliable graphene doping, we have carried out density functional theory calculations and explored the feasibility of converting p-type NGRs into n-type by introducing additional dopant candidates atoms (B, C, O, F, Al, Si, P, S, and Cl). Evaluating the relative formation energies of various binary-doped NGRs and the change in their electronic structure, we conclude that B and P atoms are promising candidates to achieve robust n-type NGRs. The origin of such p- to n-type change is analyzed based on the crystal orbital Hamiltonian population analysis. Implications of our findings in the context of electronic and energy device applications will be also discussed.

• YAKHAK HOEJI
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• v.41 no.5
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• pp.554-558
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• 1997

Two alkaloidal components were isolated from the ether soluble part of the MeOH extract of the root bark of Euonymus japonica. Their structures were elucidated by the spe ctroscopic analylses as the sesquiterpene pyridine alkaloids derived from polyester sesquiterpenes which are characteristically detected in Celastraceae plants. These include macrocycle formed by two ester linkages between dihydro-${\beta}$-agarofuran nucleus and pyridinic dibasic acid(compound 1:evoninic acid, compound 2:wilfordic acid). The structure of compound $1[C_{47}H_{50}N_2O_{17},\;mp\;161{\sim}163^{circ}C$. $[{\alpha}]_D^{28}=+31.6^{\circ}$(c, 0.1 in EtOH)] was determined as novel structure named as euojaponine N, and compound $2[C_{48}H_{57}NO_{18},\;mp\;142{\sim}145^{circ}C,\;[{\alpha}_D^{27}=+27.0^{\circ}$(c, 0.1 in EtOH)] was identified as ebenifoline W-I reported from Maytenus ebenifolia.

• Proceeding of EDISON Challenge
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• 2013.04a
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• pp.256-259
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• 2013

We investigate co-doping effects of conjugated P-N B-N with increasing of N concentration in the graphene sheets using a first principles based on the density functional theory. N doping sites of the graphene consider two possible sites (pyridinic and porphyrin-like). Energy calculation shows that additional doping of B atom in the porphyrin-like N doped graphene ($V+B-N_x$) is hard to form. At the low chemical potential of N, one N atom with additional doping in the graphene ($V+P-N_1$, $P/B-N_1$) has low formation energy on the other hand at high chemical potential of N, high concentration of N ($V+P-N_4$, $P/B-N_3$) in the graphene is governing conformation. From the results of electronic band structure calculation, it is found that $V+P-N_4$ and $P/B-N_3$ cases change the Fermi energy therefore type change is occurred. On the other hand, the cases of $V+P-N_1$ and N+B recover the electronic structure of pristine graphene.