Stability and Core-Level Signature of Nitrogen Dopants in

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Chemistry of Materials

Stability and Core-level Signature of Nitrogen Dopants in Carbonaceous Materials

Ziqi Tian,1 Sheng Dai,2,3 De-en Jiang1,* 1

2

Department of Chemistry, University of California, Riverside, California 92521, United States

Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6201, United States

3

Department of Chemistry, The University of Tennessee, Knoxville, Tennessee 37996-1600, United States

*To whom correspondence should be addressed. E-mail: [email protected]. Telephone: +1-951-827-4430

ACS Paragon Plus Environment


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Abstract Nitrogen doping is an important strategy in tuning the properties and functions of carbonaceous materials. But the chemical speciation of the nitrogen groups in the sp2-carbon framework has not been firmly established. Here we address two important questions in nitrogen doping of carbonaceous materials from a computational approach: the relative stability of different nitrogen groups and their X-ray photoelectron spectrum (XPS) signatures of the corelevel (N 1s) electron binding energies. Four types of nitrogen groups (graphitic, pyrrolic, azapyrrolic, and pyridinic) in 69 model compounds have been examined. Computed formation energies indicate that pyrrolic and pyridinic nitrogens are significantly more stable (by about 110 kJ/mol) than graphitic and aza-pyrrolic nitrogens. This stability trend can be understood from the Clar’s sextet rule. Predicted N 1s binding energies show relatively high consistency among each dopant type, thereby offering a guide to identify nitrogen groups. The relative stability coupled with predicted N 1s binding energies can explain the temperature-dependent change in the experimental XPS spectra. The present work therefore provides fundamental insights into nitrogen dopants in carbonaceous materials, which will be useful in understanding the applications of nitrogen-doped carbons in electric energy storage, electrocatalysis, and carbon capture.


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Introduction Porous carbonaceous materials have attracted considerable attention because of their high surface area, tunable pore size, electronic conductivity, and chemical functionality. They are used in gas storage/capture,1-8 supercapacitors,9-14 catalysis,15-17 and sensor technology.18-19 A wide variety of organic sources such as polymers, ionic liquids, coals, and biomass can be utilized as the precursors to make carbonaceous materials. Beyond traditional microporous activated pores derived directly from biomass such coconut shells, template methods have been used to synthesize mesoporous carbon materials8, 20-23 while carbides have been used to derive microporous carbons.24-27 Functionalization and activation have been key to further improving desired properties of porous carbons. Nitrogen doping has been widely employed to improve the performance of porous carbons for CO2 capture,28-29 oxygen reduction reaction in electrocatalysis,30-31 and supercapactiors.32-33 Nitrogen can be introduced from either nitrogen-containing precursors or activation with ammonia. However, limited information is available about the different nitrogen functional groups and their chemical environments in carbonaceous materials as a function of heat-treatment temperature due to their amorphous nature. Three typical kinds of nitrogen groups are often cited and discussed in experimental literature, namely, pyridinic, pyrrolic, and graphitic types,34-35 while most carbon atoms in these materials have sp2 hybridization.35 The weight content of nitrogen can range from 5% to 10%. There are several experimental approaches for understanding nitrogen doping. Fourier transform infrared spectroscopy (FTIR) and 13C-NMR provide information about chemical bonds between nitrogen and carbon atoms.28 In comparison, XPS characterizes chemical environment of nitrogen directly and is widely applied in identification of nitrogen dopants.34-35 However, N



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1s binding energies from XPS are usually composed of overlapping of broad bands, making it difficult to point out which kinds of nitrogen exist. X-ray absorption near edge structure (XANES) is very effective in analysis of nitrogen types in amorphous structures, but its application is limited by the need of a synchrotron source.36-37 XPS and XANES studies suggested that pyrrolic nitrogen is dominating in natural carbon materials, such as coal and asphalt,36, 38 while several other studies suggested that the graphitic type should be the most stable species in artificial carbonaceous structures.15, 30 In addition, aza-pyrrolic nitrogen was sometimes used to represent the pyrrolic nitrogen,39-41 though they are very different chemically. The often confusing reports regarding the chemical identities of nitrogen groups in N-doped carbons prompted us to address the relative stability of various nitrogen types in carbons from first principles and to provide a quantitative prediction of the N 1s binding energies that can be directly compared with the experimental XPS data which are easily obtainable. To model the different nitrogen functionalities, herein we designed close to 70 nitrogendoped graphene fragments. Subsequently, their energies of formation were calculated with a high-level ab initio method to evaluate their relative stability. Based on well-known experimental XPS data of N 1s binding energies for nitrogen-containing molecules, a scaling factor between the experimental N 1s binding energy and the theoretical N 1s orbital energy was established. This scaling factor allowed us to predict N 1s XPS spectra for different nitrogen functional groups.

Method Structures of various nitrogen-doping graphene fragments were optimized with the resolution-ofidentity (RI) Møller–Plesset perturbation theory at the second order (MP2) method in Turbomole 6.5 software package.42 To obtain accurate energies of compounds, second-generation triple-ζ


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valence basis sets with heavy polarization (def2-TZVPP) were employed. The relative stabilities of model nitrogen-doped carbon fragments were evaluated by their formation energies, ∆Ef. The energy of graphite is needed to compute the formation energies directly, but this is not possible with Turbomole, a quantum chemistry code for molecules. To avoid this issue, we computed ∆Ef indirectly by using the thermodynamic cycle in Scheme 1 following two steps: step 1, graphite is converted to CO2; step 2, CO2, N2, and H2 are converted to CnHmN, the nitrogen-containing model compound. ∆Ef(CnHmN) is therefore calculated as ∆ ∆ ∆ , where the experimental reference data was used for ∆Ef(CO2)43 while ∆ was computed

according to ∆

.

Scheme 1. The thermodynamic cycle for computing the formation energy (∆Ef) of CnHmN, a nitrogen-containing model compound.

We simulated N 1s binding energies from Koopmans’ Theorem, which states that ionization energy (namely, the binding energy of an orbital electron) is approximately the negative of the orbital energy. Using this approach, Zuilhof has showed that the C1s XPS spectra of a wide range of organic compounds are in good agreement with experiment.44 Natural bond



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orbital (NBO) analysis was employed to obtain the core-level (N 1s) orbital energies.45 We first benchmarked the N 1s binding energies of a set of 20 nitrogen-containing molecules whose experimental N 1s binding energies were known. Nearly linear correlation was found at three tested theoretical levels [B3LYP/cc-pVTZ//B3LYP/6-311G(d,p), M06-2x/cc-pVTZ//M06-2x/6311G(d,p) and MP2/cc-pVTZ//B3LYP/6-311G(d,p)]. We chose B3LYP/cc-pVTZ//B3LYP/6311G(d,p) for its computational efficiency. From the linear correlation, we obtained a scaling factor that was used to predict N 1s binding energies for nitrogen dopants in the model compounds. The N 1s binding energies calculations were carried out with the Gaussian 09 software package.46 Here we note that our approach considers only the initial-state effect, which has been shown to be valid for relative N 1s binding energies in carbon materials.47-48 However, this approximation may not be applicable to other elements and one may need to take the finalstate effect (core-hole interaction) into account, as in the case of C 1s binding energies.49

Results and discussion Three types of nitrogen groups are most often discussed in the experimental literature of nitrogen-doped carbons: graphitic (also called quaternary), pyrrolic, and pyridinic. Besides the three, one other possibility is aza-pyrrolic, which has been examined in several recent computational studies.39-41 Our goal was to compare the relative stability of these four types of nitrogen groups, so we designed many model compounds for each type, as shown in Figure 1. We first examine their relative stability.


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Figure 1. Nitrogen-containing compounds studied in this work.

Thermal stabilities of various N types. The stabilities of the four nitrogen types were evaluated with energies of formation, ∆Ef. Figure 2 shows ∆Ef vs. molecular weight for the 69 model compounds from Figure 1 as classified according to the four types of nitrogen groups. Since ∆Ef, computed here on a per-molecule basis, is dictated by the number of bonds in a model compound, it therefore roughly scales with the size and hence molecular weight of the model compound.



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Indeed, we found good linear relationships between molecular weight and calculated ∆Ef for each nitrogen type; their slopes are similar with an average R2=0.97. Our key interest is the relative stability at about the same domain size for the nitrogen-containing carbon fragment, in other words, formation energies at the same molecular weight of a model compound. If we use the average slope for all four types, we can obtain a y-offset that indicates the stability order. The relative stability values are listed in Table 1; the smaller the number the more stable the nitrogen group. One can see that pyrrolic and pyridinic nitrogens are significantly more stable than graphitic and aza-pyrrolic ones, by about 110 kJ/mol. Our results also suggest that pyrrolic nitrogen is slightly more stable than the pyridinic nitrogen, while aza-pyrrolic and graphitic nitrogens have almost the same relative stability. Here we note that our conclusion is limited to the planar geometry of our model compounds at a nitrogen doping level of 5 to 10wt%. As demonstrated previously for carbon nanotubes,50-51 curvature effect and hybridization also affect the stabilities of various nitrogen functionalities.

Figure 2. Calculated ∆Ef of various nitrogen-containing compounds.


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Table 1. Relative stabilities (∆E) of various nitrogen types N-type

∆E (kJ/mol)

Pyrrolic

12±6

Pyridinic

21±3

Graphitic

124±7

Aza-pyrrolic

127±7

We can understand the relative stabilities of the four nitrogen types via Clar’s aromatic πsextet rule, which states that a polyaromatic hydrocarbon with a larger number of aromatic πsextets (namely, benzene-like moieties) is thermodynamically more stable than its isomer with less aromatic π-sextets.52 As shown in Figure 3, the pyrrolic and pyridinic nitrogens do not change the Clar structure of the original graphene fragment, while aza-pyrrolic and graphitic nitrogens lead to one less aromatic π-sextet. Thus the pyrrolic and pyridinic nitrogens are energetically favored than aza-pyrrolic and graphitic nitrogens. In fact, the difference of the relative stability between pyrrolic/pyridinic N and graphitic/aza-pyrrolic N (~110 kJ/mol) is close to the resonance energy of pyridine (117 kJ/mol).53 Here we note that Clar’s π-sextet rule has also been used to explain the stability of N dopants in extended graphene systems.47 In addition, we found that the stability trend shown in Table 1 also manifests in the HOMO-LUMO gaps of the 69 model compounds (Figure S1 in the Supporting Information, SI): graphitic nitrogens tend to have the smallest HOMO-LUMO gaps, pyrrolic and pyridinic nitrogens the largest, and aza-pyrrolic in between.



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Figure 3. Clar’s structures after N doping of a graphene fragment: The number of the sextet rings changes from two for the graphene fragment to one for graphitic and aza-pyrrolic nitrogen doping but remains the same for pyrrolic and pyridinic nitrogen doping.

Simulation of XPS N 1s spectra. The most popular experimental technique to characterize nitrogen groups in carbons is XPS. Our next goal was to accurately predict N 1s binding energies for different nitrogen groups. To achieve this, we needed to benchmark our method against the experimental data. We chose twenty compounds which contain nitrogen in a wide range of chemical environments and whose N 1s binding energies have been measured experimentally (Figure 4). We found a very linear relationship between experimental and simulated N 1s binding energies with an R2 value of 0.95 (Figure 5). In other words, we can use the linear relationship in Figure 5 to predict N 1s binding energies for different nitrogen groups in Figure 1. The results are shown in Figure 6. One can see that the standard deviation of binding energies for each nitrogen type is relatively small; in other words, for the compounds with the same nitrogen


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type, their N 1s binding energies are quite close, especially for pyridinic nitrogens. This small dispersion will help identification of different N groups: pyridinic, graphitic, and pyrrolic nitrogens can be clearly distinguished by their N 1s binding energies. But interestingly, we found that pyridinic and azo-pyrrolic nitrogen groups have almost the same N 1s binding energies. Fortunately, aza-pyrrolic nitrogen has much lower stability than pyridinic nitrogen. Below we discuss in detail the comparison with the experimental values.

Figure 4. Reference nitrogen-containing compounds whose N 1s binding energies have been measured experimentally.



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Figure 5. Linear correlation between experimental N 1s binding energies (BEexptl) and calculated N 1s orbital energies (BEcalc).

Figure 6. Predicted N 1s binding energies for the 69 model compounds in Figure 1. The commonly assigned N 1s binding energies from XPS experiments are shown for comparison.


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Comparison with experiment. One can see from Figure 6 that the experimental values commonly assigned to graphitic, pyrrolic, and pyridinic nitrogens are in good agreement with our calculations, suggesting that the method employed predicts reasonable N 1s binding energies. Aza-pyrrolic nitrogen, which is considered to be the same as pyrrolic nitrogen in several recent theoretical papers,39-41 should have N 1s binding energies at 398.7 eV according to our prediction. The calculated N 1s binding energy of isolated pyrrole is 400.2 eV which is at the lower end of the band for pyrrolic nitrogens in Figure 6. We found that as the molecular size becomes larger, the predicted N 1s binding energy of pyrrolic nitrogen slowly shifts to larger values and levels at about 400.5 to 400.8 eV, consistent with the experimental observation that the measured N 1s binding energy of polypyrrole shifts from 399.9 to 400.7 after carbonization.1, 8 So here the key conclusion from our predicted N 1s binding energies is that aza-pyrrolic nitrogen is very different from the normal pyrrolic nitrogen in terms of N 1s binding energies and should be clearly differentiated. Combining the relative stability and the N 1s binding energies of the four nitrogen groups, we can now provide a chemical map for identifying nitrogen groups. At low temperatures, the XPS data may show three peaks around 398.8, 400.8, and 401.8 eV, corresponding to pyridinic, pyrrolic, and graphitic nitrogen, respectively. The 398.8-eV peak can also have contribution from the aza-pyrrolic nitrogen, depending on the precursor or the doping process. When temperature for the heat treatment is increased, we would see the graphitic peak gradually disappear. There would be two peaks remaining at 398.8 and 400.8 eV, corresponding to pyridinic and pyrrolic nitrogens, respectively. We think that Figure 7 would be a very useful guide for the experimentalists to understand the nitrogen identities in their carbon materials. Of course, one



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thing to note is that Figure 7 is based on thermodynamic stability and does not take into account kinetic stability that could be important especially at low temperatures.

Figure 7. A computational map for identifying nitrogen groups in carbons.

Quaternary-valley nitrogen. Besides the four popular types of nitrogen groups examined above, a much less discussed type is called the quaternary-valley nitrogen (Figure 8a), which is closely related to the graphitic nitrogen (Figure 8b).16, 54 We also examined the stability and N 1s binding energies of six model compounds containing the quaternary-valley nitrogen, in comparison with their graphitic-nitrogen counterparts (Figure S2 in SI). We found that the two types of nitrogens have very similar stability and N 1s binding energies (Figures S3 and S4 in SI). In the context of the present work, we can consider that the quaternary-valley nitrogen behaves the same as the graphitic nitrogen. Previously, the quaternary-valley nitrogen was assumed to have a N 1s binding energy 1.3 eV higher than that of the graphitic nitrogen,16 based on the partial positive


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charges on the quaternary-valley nitrogen from a semi-empirical calculation twenty years ago.54 However, our DFT and MP2 calculations show that both quaternary-valley and graphitic nitrogens have similar negative partial charges, which may explain their similar N 1s binding energies from our present prediction.

Figure 8. Quaternary-valley nitrogen (a) in comparison with graphitic nitrogen (right).

Summary and conclusions We have studied the relative stability and N 1s binding energies of nitrogen dopants in carbonaceous materials, based on about 70 model compounds of nitrogen-doped carbons. Four types of nitrogen groups were considered: graphitic, pyrrolic, aza-pyrrolic and pyridinic. Computed formation energies show that at the same domain size, pyrrolic and pyridinic nitrogen groups are much more stable than the graphitic and azo-pyrrolic nitrogens by about 110 kJ/mol. We found that pyrrolic nitrogen is slightly more stable than the pyridinic nitrogen, while graphitic and azo-pyrrolic nitrogens have almost the same stability. This stability trend can be explained by Clar’s sextet rule. Predicted N 1s binding energies after a linear correlation show that graphic, pyrrolic, and pyridinic nitrogens can be clearly distinguished and that they are consistent with the commonly used values to interpret the experimental XPS data. However, we showed that the aza-pyrrolic nitrogen should be clearly differentiated from the normal pyrrolic nitrogen since they have very different N 1s binding energies; in addition, the aza-pyrrolic



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nitrogen is much less stable than the normal pyrrolic nitrogen. We proposed a stability/N1sbinding-energy map that can help experimentalists identify nitrogen groups in nitrogen-doped carbonaceous materials.

Supporting Information HOMO-LUMO gaps of the 69 model compounds; comparison of quaternary-valley nitrogen and graphitic nitrogen for their formation energies and N 1s binding energies. This material is available free of charge via the Internet at http://pubs.acs.org.

Acknowledgement This work was supported by the Division of Chemical Sciences, Geosciences and Biosciences, Office of Basic Energy Sciences, U.S. Department of Energy. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DEAC02-05CH11231.

Reference (1)

Sevilla, M.; Valle-Vigón, P.; Fuertes, A. B. N-Doped Polypyrrole-Based Porous Carbons for CO2 Capture.

Adv. Funct. Mater. 2011, 21, 2781-2787. (2)

Zhu, X.; Hillesheim, P. C.; Mahurin, S. M.; Wang, C.; Tian, C.; Brown, S.; Luo, H.; Veith, G. M.; Han, K.

S.; Hagaman, E. W.; Liu, H.; Dai, S. Efficient CO2 Capture by Porous, Nitrogen-Doped Carbonaceous Adsorbents Derived from Task-Specific Ionic Liquids. ChemSusChem 2012, 5, 1912-1917.


Page 16 of 22

Page 17 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(3)

Hao, G.-P.; Jin, Z.-Y.; Sun, Q.; Zhang, X.-Q.; Zhang, J.-T.; Lu, A.-H. Porous Carbon Nanosheets with

Precisely Tunable Thickness and Selective CO2 Adsorption Properties. Energy Environ. Sci. 2013, 6, 3740-3747. (4)

Wei, J.; Zhou, D.; Sun, Z.; Deng, Y.; Xia, Y.; Zhao, D. A Controllable Synthesis of Rich Nitrogen-Doped

Ordered Mesoporous Carbon for CO2 Capture and Supercapacitors. Adv. Funct. Mater. 2013, 23, 2322-2328. (5)

Mahurin, S. M.; Fulvio, P. F.; Hillesheim, P. C.; Nelson, K. M.; Veith, G. M.; Dai, S. Directed Synthesis of

Nanoporous Carbons from Task-Specific Ionic Liquid Precursors for the Adsorption of CO2. ChemSusChem 2014, 7, 3284-3289. (6)

Silvestre-Albero,

A.;

Silvestre-Albero,

J.;

Martínez-Escandell,

M.;

Rodríguez-Reinoso,

F.

Micro/Mesoporous Activated Carbons Derived from Polyaniline: Promising Candidates for CO2 Adsorption. Ind. Eng. Chem. Res. 2014, 53, 15398-15405. (7)

Jalilov, A. S.; Ruan, G.; Hwang, C. C.; Schipper, D. E.; Tour, J. J.; Li, Y.; Fei, H.; Samuel, E. L.; Tour, J.

M. Asphalt-Derived High Surface Area Activated Porous Carbons for Carbon Dioxide Capture. ACS Appl. Mater. Interfaces 2015, 7, 1376-1382. (8)

Tang, J.; Liu, J.; Li, C.; Li, Y.; Tade, M. O.; Dai, S.; Yamauchi, Y. Synthesis of Nitrogen-Doped

Mesoporous Carbon Spheres with Extra-Large Pores through Assembly of Diblock Copolymer Micelles. Angew. Chem. Int. Ed. 2015, 54, 588-593. (9)

Hulicova-Jurcakova, D.; Kodama, M.; Shiraishi, S.; Hatori, H.; Zhu, Z. H.; Lu, G. Q. Nitrogen-Enriched

Nonporous Carbon Electrodes with Extraordinary Supercapacitance. Adv. Funct. Mater. 2009, 19, 1800-1809. (10)

Richey, F. W.; Dyatkin, B.; Gogotsi, Y.; Elabd, Y. A. Ion Dynamics in Porous Carbon Electrodes in

Supercapacitors Using in Situ Infrared Spectroelectrochemistry. J. Am. Chem. Soc. 2013, 135, 12818-12826. (11)

Wang, X.; Liu, C.-G.; Neff, D.; Fulvio, P. F.; Mayes, R. T.; Zhamu, A.; Fang, Q.; Chen, G.; Meyer, H. M.;

Jang, B. Z.; Dai, S. Nitrogen-Enriched Ordered Mesoporous Carbons through Direct Pyrolysis in Ammonia with Enhanced Capacitive Performance. J. Mater. Chem. A 2013, 1, 7920-7926. (12)

Zhou, D.-D.; Li, W.-Y.; Dong, X.-L.; Wang, Y.-G.; Wang, C.-X.; Xia, Y.-Y. A Nitrogen-Doped Ordered

Mesoporous Carbon Nanofiber Array for Supercapacitors. J. Mater. Chem. A 2013, 1, 8488-8496. (13)

Shen, C.; Sun, Y.; Yao, W.; Lu, Y. Facile Synthesis of Polypyrrole Nanospheres and Their Carbonized

Products for Potential Application in High-Performance Supercapacitors. Polymer 2014, 55, 2817-2824.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(14)

Page 18 of 22

Zhang, C.; Hatzell, K. B.; Boota, M.; Dyatkin, B.; Beidaghi, M.; Long, D.; Qiao, W.; Kumbur, E. C.;

Gogotsi, Y. Highly Porous Carbon Spheres for Electrochemical Capacitors and Capacitive Flowable Suspension Electrodes. Carbon 2014, 77, 155-164. (15)

Tian, X.; Su, F.; Zhao, X. S. Sulfonated Polypyrrole Nanospheres as a Solid Acid Catalyst. Green Chem.

2008, 10, 951-956. (16)

Sharifi, T.; Hu, G.; Jia, X. E.; Wagberg, T. Formation of Active Sites for Oxygen Reduction Reactions by

Transformation of Nitrogen Functionalities in Nitrogen-Doped Carbon Nanotubes. ACS Nano 2012, 6, 8904-8912. (17)

Liang, H. W.; Wei, W.; Wu, Z. S.; Feng, X.; Mullen, K. Mesoporous Metal-Nitrogen-Doped Carbon

Electrocatalysts for Highly Efficient Oxygen Reduction Reaction. J. Am. Chem. Soc. 2013, 135, 16002-16005. (18)

Li, S.-M.; Yang, S.-Y.; Wang, Y.-S.; Lien, C.-H.; Tien, H.-W.; Hsiao, S.-T.; Liao, W.-H.; Tsai, H.-P.;

Chang, C.-L.; Ma, C.-C. M.; Hu, C.-C. Controllable Synthesis of Nitrogen-Doped Graphene and Its Effect on the Simultaneous Electrochemical Determination of Ascorbic Acid, Dopamine, and Uric Acid. Carbon 2013, 59, 418429. (19)

Rasines, G.; Lavela, P.; Macías, C.; Zafra, M. C.; Tirado, J. L.; Parra, J. B.; Ania, C. O. N-Doped

Monolithic Carbon Aerogel Electrodes with Optimized Features for the Electrosorption of Ions. Carbon 2015, 83, 262-274. (20)

Liang, C. D.; Li, Z. J.; Dai, S. Mesoporous Carbon Materials: Synthesis and Modification. Angew. Chem.

Int. Ed. 2008, 47, 3696-3717. (21)

Wang, X. Q.; Zhu, Q.; Mahurin, S. M.; Liang, C. D.; Dai, S. Preparation of Free-Standing High Quality

Mesoporous Carbon Membranes. Carbon 2010, 48, 557-560. (22)

Fellinger, T. P.; White, R. J.; Titirici, M. M.; Antonietti, M. Borax-Mediated Formation of Carbon

Aerogels from Glucose. Adv. Funct. Mater. 2012, 22, 3254-3260. (23)

Zhang, P. F.; Gong, Y. T.; Wei, Z. Z.; Wang, J.; Zhang, Z. Y.; Li, H. R.; Dai, S.; Wang, Y. Updating

Biomass into Functional Carbon Material in Ionothermal Manner. ACS Appl. Mater. Interfaces 2014, 6, 1251512522. (24)

Gogotsi, Y.; Nikitin, A.; Ye, H. H.; Zhou, W.; Fischer, J. E.; Yi, B.; Foley, H. C.; Barsoum, M. W.

Nanoporous Carbide-Derived Carbon with Tunable Pore Size. Nat. Mater. 2003, 2, 591-594.


Page 19 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(25)

Yushin, G. N.; Hoffman, E. N.; Nikitin, A.; Ye, H. H.; Barsoum, M. W.; Gogotsi, Y. Synthesis of

Nanoporous Carbide-Derived Carbon by Chlorination of Titanium Silicon Carbide. Carbon 2005, 43, 2075-2082. (26)

Dash, R.; Chmiola, J.; Yushin, G.; Gogotsi, Y.; Laudisio, G.; Singer, J.; Fischer, J.; Kucheyev, S. Titanium

Carbide Derived Nanoporous Carbon for Energy-Related Applications. Carbon 2006, 44, 2489-2497. (27)

Merlet, C.; Rotenberg, B.; Madden, P. A.; Taberna, P. L.; Simon, P.; Gogotsi, Y.; Salanne, M. On the

Molecular Origin of Supercapacitance in Nanoporous Carbon Electrodes. Nat. Mater. 2012, 11, 306-310. (28)

Zhu, X.; Tian, C.; Mahurin, S. M.; Chai, S. H.; Wang, C.; Brown, S.; Veith, G. M.; Luo, H.; Liu, H.; Dai, S.

A Superacid-Catalyzed Synthesis of Porous Membranes Based on Triazine Frameworks for CO2 Separation. J. Am. Chem. Soc. 2012, 134, 10478-10484. (29)

Hwang, C. C.; Tour, J. J.; Kittrell, C.; Espinal, L.; Alemany, L. B.; Tour, J. M. Capturing Carbon Dioxide

as a Polymer from Natural Gas. Nat. Commun. 2014, 5, 3961. (30)

Gong, K. P.; Du, F.; Xia, Z. H.; Durstock, M.; Dai, L. M. Nitrogen-Doped Carbon Nanotube Arrays with

High Electrocatalytic Activity for Oxygen Reduction. Science 2009, 323, 760-764. (31)

Chen, S.; Bi, J.; Zhao, Y.; Yang, L.; Zhang, C.; Ma, Y.; Wu, Q.; Wang, X.; Hu, Z. Nitrogen-Doped Carbon

Nanocages as Efficient Metal-Free Electrocatalysts for Oxygen Reduction Reaction. Adv. Mater. 2012, 24, 55935597. (32)

Jeong, H. M.; Lee, J. W.; Shin, W. H.; Choi, Y. J.; Shin, H. J.; Kang, J. K.; Choi, J. W. Nitrogen-Doped

Graphene for High-Performance Ultracapacitors and the Importance of Nitrogen-Doped Sites at Basal Planes. Nano Lett. 2011, 11, 2472-2477. (33)

Hulicova, D.; Yamashita, J.; Soneda, Y.; Hatori, H.; Kodama, M. Supercapacitors Prepared from

Melamine-Based Carbon. Chem. Mater. 2005, 17, 1241-1247. (34)

Gammon, W. J.; Kraft, O.; Reilly, A. C.; Holloway, B. C. Experimental Comparison of N(1s) X-Ray

Photoelectron Spectroscopy Binding Energies of Hard and Elastic Amorphous Carbon Nitride Films with Reference Organic Compounds. Carbon 2003, 41, 1917-1923. (35)

Weidenthaler, C.; Lu, A.-H.; Schmidt, W.; Schüth, F. X-Ray Photoelectron Spectroscopic Studies of PAN-

Based Ordered Mesoporous Carbons (OMC). Microporous Mesoporous Mater. 2006, 88, 238-243. (36)

Kirtley, S. M.; Mullins, O. C.; Vanelp, J.; Cramer, S. P. Nitrogen Chemical-Structure in Petroleum

Asphaltene and Coal by X-Ray Absorption-Spectroscopy. Fuel 1993, 72, 133-135.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(37)

Page 20 of 22

Zhang, L. S.; Liang, X. Q.; Song, W. G.; Wu, Z. Y. Identification of the Nitrogen Species on N-Doped

Graphene Layers and Pt/NG Composite Catalyst for Direct Methanol Fuel Cell. Phys. Chem. Chem. Phys. 2010, 12, 12055-12059. (38)

Kelemen, S. R.; Gorbaty, M. L.; Kwiatek, P. J. Quantification of Nitrogen Forms in Argonne Premium

Coals. Energy Fuels 1994, 8, 896-906. (39)

Ma, C.; Shao, X.; Cao, D. Nitrogen-Doped Graphene Nanosheets as Anode Materials for Lithium Ion

Batteries: a First-Principles Study. J. Mater. Chem. 2012, 22, 8911-8915. (40)

Yu, Y. X. Can All Nitrogen-Doped Defects Improve the Performance of Graphene Anode Materials for

Lithium-Ion Batteries? Phys. Chem. Chem. Phys. 2013, 15, 16819-16827. (41)

Rangel, E.; Magana, L. F.; Sansores, L. E. A Theoretical Study of the Interaction of Hydrogen and Oxygen

with Palladium or Gold Adsorbed on Pyridine-Like Nitrogen-Doped Graphene. ChemPhysChem 2014, 15, 40424048. (42)

Ahlrichs, R.; Bar, M.; Haser, M.; Horn, H.; Kolmel, C. Electronic-Structure Calculations on Workstation

Computers - the Program System Turbomole. Chem. Phys. Lett. 1989, 162, 165-169. (43)

Cox, J. D.; Wagman, D. D.; Medvedev, V. A., CODATA Key Values for Thermodynamics. Hemisphere

Publishing Corp.: New York, 1984. (44)

Giesbers, M.; Marcelis, A. T.; Zuilhof, H. Simulation of XPS C1s Spectra of Organic Monolayers by

Quantum Chemical Methods. Langmuir 2013, 29, 4782-4788. (45)

Glendening, E. D.; Reed, A. E.; Carpenter, J. E.; Weinhold, F. NBO Version 3.1.

(46)

Frisch, M. J. T., G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.;

Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A.; Peralta, Jr., J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Keith, T.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G.


Page 21 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J.. Gaussian 09, Revision D.01, Gaussian, Inc.: Wallingford CT, 2009. (47)

Hou, Z. F.; Wang, X. L.; Ikeda, T.; Terakura, K.; Oshima, M.; Kakimoto, M. Electronic Structure of N-

Doped Graphene with Native Point Defects. Phys. Rev. B 2013, 87, 165401. (48)

Wang, X. L.; Hou, Z. F.; Ikeda, T.; Oshima, M.; Kakimoto, M.; Terakura, K. Theoretical Characterization

of X-ray Absorption, Emission, and Photoelectron Spectra of Nitrogen Doped along Graphene Edges. J. Phys. Chem. A 2013, 117, 579-589. (49)

Hou, Z. F.; Wang, X. L.; Ikeda, T.; Huang, S. F.; Terakura, K.; Boero, M.; Oshima, M.; Kakimoto, M.;

Miyata, S. Effect of Hydrogen Termination on Carbon K-Edge X-ray Absorption Spectra of Nanographene. J. Phys. Chem. C 2011, 115, 5392-5403. (50)

Sharifi, T.; Nitze, F.; Barzegar, H. R.; Tai, C. W.; Mazurkiewicz, M.; Malolepszy, A.; Stobinski, L.;

Wagberg, T. Nitrogen Doped Multi Walled Carbon Nanotubes Produced by CVD-Correlating XPS and Raman Spectroscopy for the Study of Nitrogen Inclusion. Carbon 2012, 50, 3535-3541. (51)

Barzegar, H. R.; Gracia-Espino, E.; Sharifi, T.; Nitze, F.; Wagberg, T. Nitrogen Doping Mechanism in

Small Diameter Single-Walled Carbon Nanotubes: Impact on Electronic Properties and Growth Selectivity. J. Phys. Chem. C 2013, 117, 25805-25816. (52)

Sola, M. Forty Years of Clar's Aromatic Pi-Sextet Rule. Front. Chem. 2013, 1, 22(21-28).

(53)

Joule, J. A.; Mills, K., Heterocyclic Chemistry (5th ed.). John Wiley & Sons: Chichester, UK, 2010.

(54)

Pels, J. R.; Kapteijn, F.; Moulijn, J. A.; Zhu, Q.; Thomas, K. M. Evolution of Nitrogen Functionalities in

Carbonaceous Materials during Pyrolysis. Carbon 1995, 33, 1641-1653.



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