1. Introduction

Graphene

2169-3439

Scientific Research Publishing

10.4236/graphene.2015.44008

Graphene-59477

Articles

Chemistry&Materials Science

The Surface Reactivity of Pure and Monohydrogenated Nanocones Formed from Graphene Sheets

hlam

A. El-Barbary

¹^*Mohamed

A. Kamel

¹Khaled

M. Eid

²Hayam

O. Taha

¹Rasha

A. Mohamed

¹Mohammed

A. Al-Khateeb

Physics Department, Faculty of Education, Ain Shams University, Cairo, Egypt

Bukairiayh for Science, Qassim University, Qassim, KSA

* E-mail:ahla_eg@yahoo.co.uk(HAE);

09092015

0404758329 July 2015accepted 6 September 9 September 2015

2014

This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/

A systematic computational study of surface reactivity for pure and mono-hydrogenated carbon nanocoes (CNCs) formed from graphene sheets as functions of disclination angle, cone size and hydrogenation sites has been investigated through density functional (DFT) calculations and at the B3LYP/3-21G level of theory. Five disclination angles (60°, 120°, 180°, 240° and 300°) are applied and at any disclination angle four structures with different sizes are studied. For comparison, pure and mono-hydrogenated boron nitride nanocones (BNNCs) with disclination angles 60°, 120°, 180°, 240° and 300° are also investigated. The hydrogenation is done on three different sites, H ^S1 (above the first neighbor atom of the apex atoms), H ^S2 (above one atom of the apex atoms) and H ^S3 (above one atom far from the apex atoms). Our calculations show that the highest surface reactivity for pure CNCs and BNNCs at disclination angles 60°, 180° and 300° is 23.50 Debye for B ₄₁N ₄₉H ₁₀ cone and at disclination angles 120° and 240° is 15.30 Debye for C ₉₄H ₁₄ cone. For mono-hydrogenated CNCs, the highest surface reactivity is 22.17 Debye for C ₉₀H ₁₀-H ^S3 cone at angle 300° and for mono-hydrogenated BNNCs the highest surface reactivity is 28.97 Debye for B ₄₁N ₄₉H ₁₀-H ^S1 cone when the hydrogen atom is adsorbed on boron atom at cone angle 240°.

Carbon Nanocones Boron Nitride Nanocones DFT Surface Reactivity Hydrogenation

1. Introduction

The hallow shape and the curvature of CNTs that are not present in bulk graphite make them easier to storage hydrogen inside and outside the tube surface. At the same line, one of the most important applications of CNCs (representing the fifth allotropic form of carbon) is hydrogen storage. Hydrogen storage on CNCs has been explored theoretically [1] -[10] and experimentally [11] -[13] . In addition, the fabrication of CNCs has attracted attention because of their mechanical stability and sharp tip structures [14] [15] . Also, CNCs can be used as practical phononic devices, scanning probe tips and electron field emitters [16] -[18] . The field emission properties of cone-shaped CNTs whose tip are stacked by CNCs have been investigated [19] . Furthermore, decorating the network of carbon nanostructures by nitrogen and boron has been studied [20] -[22] . The main problem of hydrogen storage is that a hydrogen fuel-cell must be of comparable weight and size to current gas tanks for the technology to gain acceptance where the determined hydrogen storage density of 9 wt% is required. Therefore, the main idea behind this work is to investigate the ability of CNCs and BNNCs for hydrogen storage via surface reactivity study. By increasing the surface reactivity, the ability of hydrogen storage is expected to be increased. To provide a better understanding of surface reactivity, pure CNCs and BNNCs, in addition to mono- hydrogenated CNCs and BNNCs are studied. Five disclination angles 60˚, 120˚, 180˚, 240˚ and 300˚ are applied on graphene sheet and the cones 60˚, cones 120˚, cones 180˚, cones 240˚ and cones 300˚ are obtained. At any disclination angle for CNCs and BNNCs, four structures with different sizes are studied in order to understand the effect of the size on the surface reactivity of NCs, except for BNNCs with disclination angles 60˚, 180˚ and 300˚ eight structures for each disclination angle are studied. Also, the hydrogenation is done on three different sites, H^S1 (above the first neighbor atom of the apex atoms), H^S2 (above one atom of the apex atoms) and H^S3 (above one atom far from the apex atoms). Hopefully, these results could be useful for testing the capability of CNCs and BNNs as hydrogen storage systems.

2. Methodology

Density Functional Theory (DFT) calculations have been performed employing the B3LYP exchange-correla- tion functional [23] [24] and the 3-21G standard basis set as implemented in the Gaussian 03W program [25] [26] . The samples of study are pure and mono-hydrogenated CNCs and BNNCs with five disclination angles, 60˚ (a five-membered ring at the apex), 120˚ (a four-membered ring at the apex), 180˚ (a three-membered ring at the apex), 240˚ (a bicyclic system at the apex) and 300˚ (a complex with a three-membered and four-membered rings at the apex), see Figure 1. The hydrogenation is done on three different sites, H^S1 (above the first neighbor

Figure 1 Optimized structures of CNCs and BNNCs: (a) and (f) cones 60˚, (b) and (g) cones 120˚, (c) and (h) cones 180˚, (d) and (i) cones 240˚, (e) and (j) cones 300˚. Grey atoms represent carbon atoms, blue atoms represent nitrogen atom and pink atoms represent boron atoms. Arrows refer to the bonds between connected atoms edges (boron atoms, model M2)

atom of the apex atoms), H^S2 (above one atom of the apex atoms) and H^S3 (above one atom far from the apex atoms). To avoid the dangling effects, the hydrogen atoms have been used to saturate the ending atoms for CNCs and BNNCs. All the atomic geometries of pure and mono-hydrogenated CNCs and BNNCs have been allowed to fully relaxation during the optimization processes.

3. Results3.1. Geometric Structures of CNCs and BNNCs

The CNCs are consisting of curved graphite sheets formed as open cones and are constructed by cutting out sectors of n × 60˚ (n = 1 - 5) from the flat sheet of graphene and connecting the edges. In the present work, we have investigated cone 60˚ (a five-membered ring at the apex), cone 120˚ (a four-membered ring), cone 180˚ (a three-memberedring), cone 240˚ (a bicyclic system), and cone 300˚ (a complex with a three-membered and four- membered rings at the apex), see Figures 1(a)-(e). At the same line the BNNCs are constructed, see Figures 1(f)-(j). For all CNCs and BNNCs with disclination angles 120˚ and 240˚, there is only one model. However, for BNNCs with disclination angles 60˚, 180˚, and 300˚ there are two models (M1 and M2), resulting from the connected atoms edges can be either nitrogen atoms (named M1) or can be boron atoms (named M2).

3.2. Surface Reactivity of Pure CNCs and BNNCs

The surface reactivity of pure CNCs and BNNCs at different disclination angels n × 60˚ (n = 1 to 5) are studied. Also, at any disclination angle the effect of the cone size is tested through working on four different structures. By this way, one can test the effects of size, disclination angle and types of NCs on the surface reactivity of NCs.

The surface reactivity of CNCs and BNNCs at disclination angle 60˚ is investigated and is listed in Table 1. The dipole moments are calculated and are used as indicator for the surface reactivity [27] [28] where the high values of the dipole moments indicate the high surface reactivity and vice versa. As shown in Table 1, the surface reactivity of cone 60˚ is increased by increasing the cone size. Also, it found that the B₈₂N₈₇H₃₀ (M1) cone 60˚ possesses the highest surface reactivity (13.1 Debye), followed by C₁₆₉H₃₀ cone 60˚ (12.1 Debye) and the smallest surface reactivity is for B₈₇N₈₂H₃₀ (M2) cone 60˚ (7.1 Debye). In other words, by increasing the number of nitrogen atoms (in case of the type of connected atoms edges is nitrogen atoms) and decreasing the number of boron atoms, the surface reactivity of BNNCs is increased.

Table 2 shows the calculated surface reactivity of CNCs and BNNCs at disclination angle 120˚. It is found that the calculated surface reactivity of cones 120˚ is increased by increasing the cone size. Also, it is noticed that the surface reactivity of the C₁₃₆H₂₄ cone 120˚ (13.6 Debye) is higher than the surface reactivity of B₆₈N₆₈H₂₄ cones 120˚ (9.2 Debye). This indicates that when the number of boron atoms is equal to number of nitrogen atoms (i.e. type of connected atoms edges is both of nitrogen and boron atoms), the surface reactivity of BNNCs is reduced. From Table 1 and Table 2, it is clear that by increasing the disclination angle (from cones 60˚ to cones 120˚), the surface reactivity is increased for both of CNCs and BNNCs.

The surface reactivity of CNCs and BNNCs at disclination angle 180˚ is listed in Table 3. As shown in Table 3, the surface reactivity of cones180˚ is increased by increasing the cone size. Also, it is found that the

Table 1 The configuration structures and the dipole moments of the CNCs 60˚ and BNNCs 60˚. The dipole moment is given by Debye

Stoichiometry cones 60˚	N	M	Y	C_n+mH_y	B_nN_mH_y M1	B_mN_nH_y M2
Stoichiometry cones 60˚	N	M	Y	Dipole moment/Debye
St1	21	24	15	5.4	7.2	4.9
St2	38	42	20	7.9	9.5	5.5
St3	56	59	25	9.2	9.8	6.6
St4	82	87	30	12.1	13.1	7.1

M1 refers to the type of connected atoms edges is nitrogen atoms, M2 refers to the type of connected atoms edges is boron atoms.

Table 2 The configuration structures and the dipole moments of the CNCs 120˚ and BNNCs 120˚. The dipole moment is given by Debye

Stoichiometry cones 120˚	M	Y	C_2mH_y	B_mN_mH_y
Stoichiometry cones 120˚	M	Y	Dipole moment/Debye
St1	18	12	6.1	5.1
St2	28	16	8.0	5.7
St3	46	20	10.7	7.5
St4	68	24	13.6	9.2

Table 3 The configuration structures and the dipole moments of the CNCs 180˚ and BNNCs 180˚. The dipole moment is given by Debye

Stoichiometry cones 180˚	N	M	Y	C_n+mH_y	B_nN_mH_y M1	B_mN_nH_y M2
Stoichiometry cones 180˚	N	M	Y	Dipole moment/Debye
St1	22	26	12	7.8	12.1	7.1
St2	35	40	15	9.3	13.1	8.9
St3	49	53	18	9.8	15.2	9.4
St4	68	73	21	11.5	15.9	11.2

B₆₈N₇₃H₂₁ (M1) cone 180˚ possesses the highest surface reactivity (15.9 Debye), followed by C₁₄₁H₂₁ cone 180˚ (11.5 Debye) and the smallest surface reactivity is for B₇₃N₆₈H₂₁ (M2) cone 180˚ (11.2 Debye). In addition, the surface reactivity of cones 180˚ is found to be higher than the surface reactivity of the cones 120˚ and the latter is higher than the cones 60˚.

From Table 4, the calculated surface reactivity of CNCs and BNNCs at disclination angle 240˚ is increased by increasing the cone size. Also, it is found that the surface reactivity of the C₉₄H₁₄ cone 240˚ (15.3 Debye) is higher than the surface reactivity of B₄₇N₄₇H₁₄ cone 240˚ (11.9 Debye). From Tables 1-4, it is clear that by increasing the disclination angle (from cones 60˚ to cones 240˚), the surface reactivity is increased.

The surface reactivity of CNCs and BNNCs at disclination angle 300˚ is shown in Table 5. It is found that the surface reactivity of cones 300˚ is increased by increasing the cone size. Also, it is found that the B₄₁N₄₉H₁₀ (M1) cone 300˚ possesses the highest surface reactivity (23.5 Debye), followed by C₉₀H₁₀ cone 300˚ (23.5 Debye) and the smallest surface reactivity is for B₄₉N₄₁H₁₀ (M2) cone 300˚ (12.5 Debye).

From Tables 1-5, one can report that the surface reactivity is increased by increasing the cone size and the disclination angle. In addition, the highest surface reactivity is for B_nN_mH_y (M1) cones when the type of connected atoms edges is nitrogen atoms (at disclination angles 60˚, 180˚ and 300˚), otherwise the surface reactivity of C_2mH_y cones is always higher than B_mN_mH_y cones (at disclination angles 120˚ and 240˚).

3.3. Surface Reactivity of Mono-Hydrogenated CNCs and BNNCs

The surface reactivity of mono-hydrogenated CNCs at three different hydrogenation sites H^S1 (above the first neighbor atom of the apex atoms), H^S2 (above one atom of the apex atoms) and H^S3 (above one atom far from the apex atoms) for each disclination angels n × 60˚ (n = 1 to 5) are studied, see Figure 2. Also, at any disclination angle the effect of the cone size is tested through working on four different structures. By this way, one can test the effects of size, disclination angle and hydrogenation site of CNCs on the surface reactivity of mono- hydrogenated CNCs. From Table 6, it is found that the surface reactivity of mono-hydrogenated CNCs is increased by increasing the size and dsiclination angles of CNCs. Also, the surface reactivity at hydrogenation site H^S3 always possesses the highest dipole moment, followed by H^S1 and H^S2 sites. The highest surface reactivities at disclination angles 60˚, 120˚, 180˚, 240˚ and 300˚ are found to be 10.94 Debye for C₁₇₀H₃₀-H^S1, 12.58 Debye for C₁₃₆H₂₄-H^S3, 18.70 Debye for C₁₄₁H₂₁-H^S1, 16.98 Debye for C₉₄H₁₄-H^S3 and 22.17 Debye for C₉₀H₁₀-H^S3, respectively. Finally, on can conclude that the best cone size, the best hydrogenation site and best disclination angle for hydrogen adsorption is for CNC C₉₀H₁₀-H^S3 at 300˚ declination angle.

Table 4 The configuration structures and the dipole moments of the CNCs 240˚ and BNNCs 240˚. The dipole moment is given by Debye

Stoichiometry cones 240˚	M	Y	C_2mH_y	B_mN_mH_y
Stoichiometry cones 240˚	M	Y	Dipole moment/Debye
St1	14	8	8.0	7.9
St2	23	10	11.8	9.0
St3	34	12	12.0	10.0
St4	47	14	15.3	11.9

Table 5 The configuration structures and the dipole moments of the CNCs 300˚ and BNNCs 300˚. The dipole moment is given by Debye

Stoichiometry cones 300˚	N	M	Y	C_n+mH_y	B_nN_mH_y M1	B_mN_nH_y M2
Stoichiometry cones 300˚	N	M	Y	Dipole moment/Debye
St1	15	19	6	11.2	11.7	8.0
St2	21	26	7	12.8	13.4	10.4
St3	34	41	9	18.6	19.0	10.9
St4	41	49	10	21.9	23.5	12.5

Table 6 The configuration structures and the dipole moments of mono-hydrogenated CNCs. The dipole moment is given by Debye

Angle 60˚		Angle 120˚		Angle 180˚		Angle 240˚		Angle 300˚
Systems	Dipole moment	Systems	Dipole moment	Systems	Dipole moment	Systems	Dipole moment	Systems	Dipole moment
C₄₅H₁₅-H^S1 C₄₅H₁₅-H^S2 C₄₅H₁₅-H^S3	5.63 3.65 5.02	C₃₆H₁₂-H^S1 C₃₆H₁₂-H^S2 C₃₆H₁₂-H^S3	5.87 4.93 6.11	C₄₈H₁₂-H^S1 C₄₈H₁₂-H^S2 C₄₈H₁₂-H^S3	7.60 7.17 8.43	C₂₈H₈-H^S1 C₂₈H₈-H^S2 C₂₈H₈-H^S3	3.16 3.68 5.54	C₂₃H₅-H^S1 C₂₃H₅-H^S2 C₂₃H₅-H^S3	3.22 2.46 5.88
C₈₀H₂₀-H^S1 C₈₀H₂₀-H^S2 C₈₀H₂₀-H^S3	6.92 6.03 7.09	C₅₆H₁₆-H^S1 C₅₆H₁₆-H^S2 C₅₆H₁₆-H^S3	6.94 6.38 7.42	C₇₅H₁₅-H^S1 C₇₅H₁₅-H^S2 C₇₅H₁₅-H^S3	12.73 10.46 11.26	C₄₆H₁₀-H^S1 C₄₆H₁₀-H^S2 C₄₆H₁₀-H^S3	6.67 6.01 6.93	C₃₄H₆-H^S1 C₃₄H₆-H^S2 C₃₄H₆-H^S3	10.31 6.72 10.42
C₁₁₅H₂₅-H^S1 C₁₁₅H₂₅-H^S2 C₁₁₅H₂₅-H^S3	9.14 6.64 7.94	C₉₂H₂₀-H^S1 C₉₂H₂₀-H^S2 C₉₂H₂₀-H^S3	8.49 8.78 10.38	C₁₀₂H₁₈-H^S1 C₁₀₂H₁₈-H^S2 C₁₀₂H₁₈-H^S3	11.23 11.65 11.98	C₆₈H₁₂-H^S1 C₆₈H₁₂-H^S2 C₆₈H₁₂-H^S3	5.92 7.81 8.53	C₅₈H₈-H^S1 C₅₈H₈-H^S2 C₅₈H₈-H^S3	15.61 12.39 13.28
C₁₇₀H₃₀-H^S1 C₁₇₀H₃₀-H^S2 C₁₇₀H₃₀-H^S3	10.94 9.52 10.79	C₁₃₆H₂₄-H^S1 C₁₃₆H₂₄-H^S2 C₁₃₆H₂₄-H^S3	12.18 11.52 12.58	C₁₄₁H₂₁-H^S1 C₁₄₁H₂₁-H^S2 C₁₄₁H₂₁-H^S3	18.70 15.99 15.55	C₉₄H₁₄-H^S1 C₉₄H₁₄-H^S2 C₉₄H₁₄-H^S3	6.73 7.51 16.98	C₉₀H₁₀-H^S1 C₉₀H₁₀-H^S2 C₉₀H₁₀-H^S3	18.38 17.93 22.17

H^S1 refers to the hydrogenation site is above the first neighbor atom of the apex atoms. H^S2 refers to the hydrogenation site is above one atom of the apex atoms. H^S3 refers to the hydrogenation site is above one atom far from the apex atoms.

Also, the surface reactivity of mono-hydrogenated BNNCs at three different hydrogenation sites H^S1, H^S2 and H^S3 for each disclination angels n × 60˚ (n = 1 to 5), are studied. The hydrogen atom can be adsorbed on boron atom (named Type1) or can be adsorbed on nitrogen atom (named Type2). As we mention above, for disclination angles 60˚, 180˚ and 300˚ there are two models of BNNCs, BNNCs-M1 (the connected edges atoms are nitrogen atoms) and BNNCs-M2 (the connected edges atoms are boron atoms). Therefore, for the surface reactivity of BNNCs at disclination angles 120˚ and 240˚ for there are two systems of BNNCs, BNNCs-Type1 and BNNCs-Type2, see Table 6. However, for disclination angles 60˚, 180˚ and 300˚ there are four systems of BNNCs, BNNCs-M1-Type1, BNNCs-M1-Type2, BNNCs-M2-type1 and BNNCs-M2-Type2, see Table 7 and Table 8.

From Table 7, it is clear that the surface reactivities for monohydrogenated BNNCs-Type1 and BNNCs-Type2

Figure 2 Schematic representation for hydrogenation sites 1-HS1, 2-HS2, 3-HS3 of CNCs with disclination angle 120˚ for structures (a) C36H12, (b) C56H16, (c) C92H20 and (d) C136H24. Circles refer to the hydrogenation sites

are increased by increasing the cone size and cone angle. For disclination angle 120˚, the highest surface reactivates for Type1 and Type2 are found to be 10.90 Debye for B₆₈N₆₈H₂₄-H^S2 and 11.75 Debye for B₆₈N₆₈H₂₄-H^S1, respectively. For disclination angle 240˚, the highest surface reactivates for Type1 and Type2 are found to be 12.85 Debye for B₄₇N₄₇H₁₄-H^S2 and 25.20 Debye for B₃₄N₃₄H₁₂-H^S3, respectively.

Table 8 shows that the surface reactivities for mono-hydrogenated BNNCs-M1-Type1 and BNNCs-M1- Type2 are increased by increasing the cone size and cone angle. For disclination angle 60˚, the highest surface reactivates for Type1 and Type2 are found to be 13.96 Debye for B₃₈N₄₂H₂₀-H^S2 and 10.77 Debye for B₈₃N₈₇H₃₀-H^S1, respectively. For disclination angle 180˚, the highest surface reactivates for Type1 and Type2 are found to be 20.81 Debye for B₆₈N₇₃H₂₁-H^S1 and 28.50 Debye for B₃₅N₄₀H₁₅-H^S3, respectively. For disclination angle 300˚, the highest surface reactivates for Type1 and Type2 are found to be 28.97 Debye for B₄₁N₄₉H₁₀-H^S1 and 27.55 Debye for B₂₆N₃₂H₈-H^S3, respectively.

From Table 9, it is found that the surface reactivities for mono-hydrogenated BNNCs-M2-Type1 and BNNCs-M2-Type2 are increased by increasing the cone size and cone angle. For disclination angle 60˚, the highest surface reactivates for Type1 and Type2 are found to be 7.44 Debye for B₈₇N₈₃H₃₀-H^S2 and 20.77 Debye for B₄₂N₃₈H₂₀-H^S1, respectively. For disclination angle 180˚, the highest surface reactivates for Type1 and Type2 are found to be 11.83 Debye and 17.28 Debye B₇₃N₆₈H₂₁-H^S3, respectively. For disclination angle 300˚, the highest surface reactivates for Type1 and Type2 are found to be 7.26 Debye and 25.94 Debye for B₃₂N₂₆H₈-H^S3, respectively. We can conclude that the best cone size, the best hydrogenation site and best disclination angle for mono-hydrogenated Type1 and Type2 of BNNCs is 28.97 Debye for B₄₁N₄₉H₁₀-H^S1 and 27.55 Debye for B₂₆N₃₂H₈-H^S3 at 300˚ declination angle.

Finally, it is found that the surface reactivity for pure and mono-hydrogenated CNCs and BNNCs is increased by increasing the cone angle and the cone size. Also, it is found that the surface reactivity is increased by hydrogenation and the highest surface reactivity is found to be 28.97 Debye for B₄₁N₄₉H₁₀-H^S1 (M1) when the hydrogenation is done on the boron atom (Type1).

Table 7 The configuration structures and the dipole moments of mono-hydrogenated BNNCs-Type1 and BNNCs-Type2 for disclination angles 120˚ and 240˚. The dipole moment is given by Debye

Angle 120˚			Angle 240˚
	Dipole moment			Dipole moment
Systems	Type1	Type2	Systems	Type1	Type2
B₁₈N₁₈H₁₂-H^S1 B₁₈N₁₈H₁₂-H^S2 B₁₈N₁₈H₁₂-H^S3	4.70 6.49 5.27	7.66 3.45 7.98	B₁₄N₁₄H₈-H^S1 B₁₄N₁₄H₈-H^S2 B₁₄N₁₄H₈-H^S3	3.43 5.67 5.97	8.22 5.67 5.81
B₂₈N₂₈H₁₆-H^S1 B₂₈N₂₈H₁₆-H^S2 B₂₈N₂₈H₁₆-H^S3	5.26 7.31 5.58	8.34 4.61 3.72	B₂₃N₂₃H₁₀-H^S1 B₂₃N₂₃H₁₀-H^S2 B₂₃N₂₃H₁₀-H^S3	5.24 8.86 7.94	10.13 7.69 12.64
B₄₆N₄₆H₂₀-H^S1 B₄₆N₄₆H₂₀-H^S2 B₄₆N₄₆H₂₀-H^S3	7.02 9.18 7.49	10.09 6.12 6.84	B₃₄N₃₄H₁₂-H^S1 B₃₄N₃₄H₁₂-H^S2 B₃₄N₃₄H₁₂-H^S³	7.10 10.88 10.19	11.97 9.60 25.20
B₆₈N₆₈H₂₄-H^S1 B₆₈N₆₈H₂₄-H^S2 B₆₈N₆₈H₂₄-H^S3	8.69 10.90 9.18	11.75 7.60 6.81	B₄₇N₄₇H₁₄-H^S1 B₄₇N₄₇H₁₄-H^S2 B₄₇N₄₇H₁₄-H^S3	8.91 12.85 11.86	13.92 11.45 16.77

Table 8 The configuration structures and the dipole moments of mono-hydrogenated BNNCs-M1-Type1 and BNNCs-M1- Type2, for disclination angles 60˚, 180˚ and 300˚. The dipole moment is given by Debye

Angle 60˚			Angle 180˚			Angle 300˚
	Dipole moment			Dipole moment			Dipole moment
Systems	Type1	Type2	Systems	Type1	Type2	Systems	Type1	Type2
B₂₁N₂₄H₁₅-H^S1 B₂₁N₂₄H₁₅-H^S2 B₂₁N₂₄H₁₅-H^S3	7.20 11.07 7.01	7.72 5.88 6.35	B₂₂N₂₆H₁₂-H^S1 B₂₂N₂₆H₁₂-H^S2 B₂₂N₂₆H₁₂-H^S3	16.37 13.65 15.68	13.57 11.70 19.98	B₁₀N₁₃H₅-H^S1 B₁₀N₁₃H₅-H^S2 B₁₀N₁₃H₅-H^S3	19.05 10.19 9.04	9.82 10.72 10.41
B₃₈N₄₂H₂₀-H^S1 B₃₈N₄₂H₂₀-H^S2 B₃₈N₄₂H₂₀-H^S3	9.47 13.90 9.49	10.56 8.03 8.32	B₃₅N₄₀H₁₅-H^S1 B₃₅N₄₀H₁₅-H^S2 B₃₅N₄₀H₁₅-H^S3	19.83 16.63 15.28	16.49 14.63 28.50	B₁₅N₁₉H₆-H^S1 B₁₅N₁₉H₆-H^S2 B₁₅N₁₉H₆-H^S3	11.06 12.56 11.95	11.48 11.90 18.29
B₄₂N₅₆H₂₅-H^S1 B₄₂N₅₆H₂₅-H^S2 B₄₂N₅₆H₂₅-H^S3	6.73 10.80 6.90	8.81 4.82 5.54	B₄₉N₅₃H₁₈-H^S1 B₄₉N₅₃H₁₈-H^S2 B₄₉N₅₃H₁₈-H^S3	17.78 14.10 13.10	14.74 12.32 13.42	B₂₆N₃₂H₈-H^S1 B₂₆N₃₂H₈-H^S2 B₂₆N₃₂H₈-H^S3	22.92 12.03 15.56	16.60 11.33 27.55
B₈₃N₈₇H₃₀-H^S1 B₈₃N₈₇H₃₀-H^S2 B₈₃N₈₇H₃₀-H^S3	8.87 13.18 8.96	10.77 10.95 7.80	B₆₈N₇₃H₂₁-H^S1 B₆₈N₇₃H₂₁-H^S2 B₆₈N₇₃H₂₁-H^S3	20.81 16.97 15.90	17.41 15.00 15.97	B₄₁N₄₉H₁₀-H^S1 B₄₁N₄₉H₁₀-H^S2 B₄₁N₄₉H₁₀-H^S3	28.97 16.79 23.17	13.07 12.04 20.51

Table 9 The configuration structures and the dipole moments of mono-hydrogenated BNNCs-M2-Type1 and BNNCs-M2- Type2, for disclination angles 60˚, 180˚ and 300˚. The dipole moment is given by Debye

Angle 60˚			Angle 180˚			Angle 300˚
Systems	Dipole moment		Systems	Dipole moment		Systems	Dipole moment
Systems	Type1	Type2	Systems	Type1	Type2	Systems	Type1	Type2
B₂₄N₂₁H₁₅-H^S1 B₂₄N₂₁H₁₅-H^S2 B₂₄N₂₁H₁₅-H^S3	4.91 5.30 5.17	17.20 10.50 4.24	B₂₆N₂₂H₁₂-H^S1 B₂₆N₂₂H₁₂-H^S2 B₂₆N₂₂H₁₂-H^S3	3.84 7.36 7.37	8.54 8.96 17.28	B₁₃N₁₀H₅-H^S1 B₁₃N₁₀H₅-H^S2 B₁₃N₁₀H₅-H^S3	4.49 4.02 1.13	3.59 2.39 8.14
B₄₂N₃₈H₂₀-H^S1 B₄₂N₃₈H₂₀-H^S2 B₄₂N₃₈H₂₀-H^S3	6.78 6.94 6.75	20.77 12.24 20.66	B₄₀N₃₅H₁₅-H^S1 B₄₀N₃₅H₁₅-H^S2 B₄₀N₃₅H₁₅-H^S3	5.54 9.21 9.27	10.28 10.64 14.37	B₁₉N₁₅H₆-H^S1 B₁₉N₁₅H₆-H^S2 B₁₉N₁₅H₆-H^S3	5.00 3.67 7.18	3.04 7.28 13.85
B₅₆N₄₂H₂₅-H^S1 B₅₆N₄₂H₂₅-H^S2 B₅₆N₄₂H₂₅-H^S3	5.38 5.89 5.54	16.40 9.43 10.73	B₅₃N₄₉H₁₈-H^S1 B₅₃N₄₉H₁₈-H^S2 B₅₃N₄₉H₁₈-H^S3	6.61 9.81 9.46	12.13 9.64 15.08	B₃₂N₂₆H₈-H^S1 B₃₂N₂₆H₈-H^S2 B₃₂N₂₆H₈-H^S3	5.66 2.80 7.26	4.37 3.04 25.94
B₈₇N₈₃H₃₀-H^S1 B₈₇N₈₃H₃₀-H^S2 B₈₇N₈₃H₃₀-H^S3	6.92 7.44 7.11	9.50 11.27 7.21	B₇₃N₆₈H₂₁-H^S1 B₇₃N₆₈H₂₁-H^S2 B₇₃N₆₈H₂₁-H^S3	8.18 11.57 11.83	13.74 11.51 11.53	B₄₉N₄₁H₁₀-H^S1 B₄₉N₄₁H₁₀-H^S2 B₄₉N₄₁H₁₀-H^S3	5.09 2.57 2.57	8.73 4.77 14.92

4. Conclusion

The surface reactivity of fifty-two structures of pure CNCs and BNNCs and two hundred and fifty-two structures for mono-hydrogenated CNCs and BNNCs is calculated using density functional (DFT) calculations at the B3LYP/3-21G level of theory. Five disclination angles (60˚, 120˚, 180˚, 240˚ and 300˚), four different nanocone sizes and three different hydrogenation sites are applied. The calculations show that the dipole moments are always increased by increasing the nanocone sizes and the highest surface reactivity for pure CNCs and BNNCs at disclination angles 60˚, 180˚ and 300˚ is 23.50 Debye for B₄₁N₄₉H₁₀ cone and at disclination angles 120˚ and 240˚ is 15.30 Debye for C₉₄H₁₄ cone. For mono-hydrogenated CNCs, the highest surface reactivity is found 22.17 Debye C₉₀H₁₀-H^S3 at CNC angle 300˚ and for mono-hydrogenated BNNCs the highest surface reactivity is 28.97 Debye for B₄₁N₄₉H₁₀-H^S1 when the hydrogen atom is adsorbed on boron atom at BNNC angle 240˚.

Cite this paper

Ahlam A.El-Barbary,Mohamed A.Kamel,Khaled M.Eid,Hayam O.Taha,Rasha A.Mohamed,Mohammed A.Al-Khateeb,11, (2015) The Surface Reactivity of Pure and Monohydrogenated Nanocones Formed from Graphene Sheets. Graphene,04,75-83. doi: 10.4236/graphene.2015.44008

NOTES

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