Long Range Functionalization of h-BN Monolayer by Carbon Doping

Subscriber access provided by - Access paid by the | UCSB Libraries

Article

Long Range Functionalization of H-BN Monolayer by Carbon Doping Min Gao, Masashi Adachi, Andrey Lyalin, and Tetsuya Taketsugu J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.5b12706 • Publication Date (Web): 15 Mar 2016 Downloaded from http://pubs.acs.org on March 19, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

The Journal of Physical Chemistry C is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 28

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

The Journal of Physical Chemistry

Long Range Functionalization of h-BN Monolayer by Carbon Doping Min Gao,† Masashi Adachi,† Andrey Lyalin,∗,‡ and Tetsuya Taketsugu∗,†,‡,¶ †Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan ‡Global Research Center for Environment and Energy Based on Nanomaterials Science (GREEN), National Institute for Materials Science (NIMS), Tsukuba 305-0044, Japan ¶Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Kyoto 615-8245, Japan E-mail: [email protected]; [email protected]

1 ACS Paragon Plus Environment


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

Abstract Adsorption and catalytic activation of the molecular oxygen on the hexagonal boron nitride (h-BN) monolayer doped with carbon atom have been studied theoretically using density functional theory. It is demonstrated that C doping in B position of hBN (CB @h-BN) produces n-type semiconductor BN material with noticeable catalytic activity for O2 activation in the large area extended far away from the C impurity. The adsorption energy of O2 on CB @h-BN decreasing slowly with the increase in distance from the CB defect, while O2 remains highly activated. No such effect is observed for monolayer h-BN doped with different atoms of group III, IV and V and transitionmetal elements, such as B, N, Al, Si, Ge, Ni, Pt, Pd, and Au, where O2 adsorbs only in the close vicinity of the dopant. It is shown that even small concentration of C dopants can functionalize the large surface area of monolayer BN making it promising catalytic material for oxygen activation and oxygen reduction reaction.

Introduction The catalytic activation of molecular oxygen is crucial for a number of important industrial chemical processes, such as selective oxidation and epoxidation, exhaust gas emission control for automotive applications, oxygen reduction reaction in fuel cells, etc. 1–5 Extensive efforts are devoted to development of effective catalytic materials for oxygen activation. Currently, most of the industrially used catalysts are based on precious transition metals (Pt, Pd, Ru, etc.), 6 which is a big challenge for commercial market. Therefore, the development of effective, cheap and environment friendly catalysts based on the non-precious abundant elements is an emerging task. Recently we have demonstrated theoretically and proved experimentally that even inert and catalytically inactive materials can be functionalized and become active catalysts at nanoscale. 7–9 Moreover, traditional inert supports under certain conditions can considerably influence physical and chemical properties of the supported nanoparticles and promote their 2 ACS Paragon Plus Environment

Page 2 of 28

Page 3 of 28

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


catalytic activity. 10–13 Our finding opens new and yet unexplored routes to design effective catalysts based on materials never before been considered for catalytic applications. One of such promising material is hexagonal boron nitride (h-BN), which is a wide band gap (5−6 eV) dielectric with high thermal and chemical stability. However, the electronic and chemical properties of BN can be considerably modified by introducing vacancy and impurity defects or dopants, 7,11,12,14,15 hybridized boron nitride and graphene domains, 16 adsorbants on the h-BN surface 17,18 or metal support. 8,9,19–28 Appearance of the defect states in the forbidden zone of BN can strongly promote electron transfer between the support and the adsorbed molecule resulting in catalytic activation of adsorbants. 11–13,29,30 Thus, presence of the defect states near the Fermi level induced by N impurity makes h-BN highly active for O2 adsorption and activation, due to the electron transfer to the antibonding 2π ∗ orbital of oxygen molecule. 7 It is important to note that the principal possibility of atomic substitutions into BN honeycomb lattice via post-synthesis treatments has been demonstrated experimentally on the example of C doping, making C-doped BN promising material for physical and chemical applications. 31–33 Recently, theoretical calculations demonstrate B atoms in BN lattice are preferably substituted by C atoms, especially when the system is positively charged. 34,35 Such substitution of B atom in BN lattice by C impurity corresponds to the one electron doping of BN producing n-type semiconductor BN material with catalytic activity for oxygen reduction reaction (ORR) and CO oxidation. 29,30 Moreover, very recently a ternary B-C-N alloy semiconductor demonstrating photocatalytic activity for hydrogen or oxygen evolution from water was synthesized. 36 It was suggested that the band gap of the B-C-N alloy can be adjusted by the amount of carbon atoms resulting in unique tunable functionality of such a material. 36 In spite of the great potential for various chemical applications, systematic studies on the unique catalytic properties of BN based materials are still in their infancy. The main question is how to functionalize an inert BN to work as an active catalysts with the predicted and desired properties? Therefore, the theoretical investigation of the catalytic properties



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

of BN based nanomaterials modified by the controlled atom doping is an important task. In the present work, we have performed a systematic investigation of catalytic activity of the C doped monolayer h-BN towards adsorption and activation of the molecular oxygen. It is demonstrated that C doping of the monolayer h-BN in B position (CB @h-BN) produces n-type semiconductor material with noticeable catalytic activity in the large area extended far away from the C impurity. The adsorption energy of O2 on CB @h-BN decreases slowly with the increase in distance from the C impurity, while O2 remains highly activated. No such effect is observed for monolayer h-BN doped with different atoms of group III, IV and V and transition-metal elements, such as B, N, Al, Si, Ge, Ni, Pt, Pd, and Au, where O2 adsorbs only in the close vicinity of the dopant. Therefore, even small concentration of C dopants can functionalize the large surface area of monolayer BN making it promising catalytic material.

Theoretical Methods The calculations are carried out using density functional theory (DFT) with the gradientcorrected exchange-correlation functional of Wu and Cohen (WC) 37 as implemented in the SIESTA code. 38–40 Double-ζ plus polarization function (DZP) basis sets are used to treat the valence electrons of B, C, N, and O atoms. 41,42 The remaining core electrons are represented by the Troullier-Martins norm-conserving pseudopotentials 43 in the Kleinman-Bylander factorized form. 44 All calculations are performed accounting for spin polarization. The energy cutoff of 200 Ry is chosen to guarantee convergence of the total energies and forces. A common energy shift of 10 meV is applied. The self-consistency of the density matrix is achieved with a tolerance of 10−4 . For geometry optimization, the conjugate-gradient approach was used with a threshold of 0.02 eV ˚ A−1 . The h-BN lattice has been optimized using the Monkhorst-Pack 45 10×10×4 k-point mesh for Brillouin zone sampling. The calculated lattice parameters a = b = 2.504 ˚ A and c = 6.656 ˚ A are in excellent agreement with the


Page 4 of 28

Page 5 of 28

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


experimental values of a = b = 2.524 ± 0.020 ˚ A and c = 6.684 ± 0.020 ˚ A. 46 The monolayer h-BN is modelled by a 12×12 slab with 144 BN units. The periodically replicated slabs are separated by the vacuum region of 25 ˚ A in the (001) direction. Only the Γ point is used for sampling the Brillouin zone due to the large size of the supercell. Periodic boundary conditions are used for all systems including free molecules. In the latter case, the size of a supercell was chosen to be large enough to make intermolecular interactions negligible. To validate our approach and choice of WC functional, we have calculated the dissociation energies and interatomic distances for O2 . The calculated dissociation energy, De , and bond length in O2 (5.88 eV, 1.24 ˚ A) are in a good agreement with experimental data (5.23 eV, 1.21 ˚ A). 47 All energies are corrected for the basis set superposition errors (BSSE). The atoms in molecules (AIM) method of Bader has been used for charge analysis. 48–50 The electron density has been plotted using XCRYSDEN visualization program. 51

Theoretical Results C doped h-BN structures In the present work we consider several BN based structures, including a pristine monolayer h-BN, a monolayer h-BN with C atom doped in B position (CB ), N position (CN ), and two C atoms in the nearest B and N positions (2 CBN ), as shown in Figure 1. All considered structures doped with C remain planar after structural relaxations, without any protrusion of C atom above the surface. The detailed analysis of the electronic structure of boron nitride sheets doped with carbon atoms has been reported in refs. 34,35,52. Figures 2a, 2b, 2c, and 2d present the spin polarized density of electronic states (DOS) calculated for the pristine monolayer h-BN, monolayer h-BN with CB , CN , and 2 CBN impurities, respectively. Our calculations demonstrate that the defect-free monolayer h-BN has a wide band gap of 4.61 eV, in a general agreement with the available experimental values widely dispersed in the range between 3.6 5 ACS Paragon Plus Environment


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

Figure 1: Surface models for (a) pristine p(12×12) h-BN slab and monolayer h-BN doped with C atom in (b) B position (CB ), (c) N position (CN ), and (d) two C atoms in B and N positions (2 CBN ). Only part of the doped slab is shown. Nitrogen atoms are blue-colored, boron atoms are gray and carbon atoms are black. and 7.1 eV. 53 Theoretical estimations reported previously give the value of the band gap from 4.6 to 8.4 eV, depending on the model approach. 35,54–58 For the sake of comparison we present the overall total DOS in Figure S1. Carbon doping of the monolayer h-BN results in a considerable change of the electronic structure and appearance of the defect levels in the forbidden zone of h-BN. 35,52 Substitution of B atom with C is equivalent to the electron doping of monolayer h-BN. Figure 2b demonstrates that in the case of CB , an occupied spin-up and an unoccupied spin-down defect levels appear just below the conductivity band, which corresponds to a typical electronic structure of n-type semiconductor. The occupied C-2p defect level of CB is located 0.94 eV below the bottom of the conduction band of h-BN, drastically affecting its electronic and chemical properties. Substitution of N atom in monolayer h-BN with C is equivalent to an electron vacancy doping. In this case an occupied spin-up and an unoccupied spin-down defect levels appear just above the valence band of h-BN (Figure 2c) producing p-type semiconductor material.


Page 6 of 28

Page 7 of 28

120

120

h

(b) C @ -BN

90

60

60

30

30

-1

90

PDOS, eV

PDOS, eV

-1

(a) h-BN

0 -30 -60

B

C-2p x40

0 -30 -60

B, N atoms

-90 -120 -10

-90

-5

0

B, N atoms

-120 -10

5

-5

Energy, eV

120

120

h

(d) C

90

x40

30 0 -30 -60 -90 -120 -10

5

0

5

h

@ -BN

BN

C-2p

60

C-2p PDOS, eV

-1

60

-1

90

N

0 Energy, eV

(c) C @ -BN

PDOS, eV

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


x40

30 0 -30 -60 -90

B, N atoms

-5

0

-120 -10

5

Energy, eV

B, N atoms

-5 Energy, eV

Figure 2: Spin polarized partial density of states (PDOS) projected on B and N (black curve) and C (red curve) atoms for (a) pristine monolayer h-BN and h-BN monolayer with (b) CB , (c) CN , and (d) 2 CBN impurities. The Fermi level is indicated by a dashed vertical line at 0 eV, arrows directed up and down indicate the up spin and down spin DOS. A Gaussian broadening of a half width 0.1 eV has been used. PDOS projected on C atoms is multiplied by 40.



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

In the case of monolayer h-BN doped with the carbon dimer, when two C atoms are located in the nearest B and N positions 2 CBN @h-BN, two occupied defect levels appear just above the valence band and two unoccupied defect levels appears close to the bottom of the conductivity band. Therefore, 2 CBN works as neither donor nor acceptor of electrons and the chemical properties of the material are not modified.

Adsorption and activation of O2 on C@h-BN systems Previously, we have demonstrated that oxygen molecule adsorbs weakly on a pristine monolayer h-BN, but readily adsorbs on h-BN with N and B impurity, NB , BN , and vacancy VB , VN point defects. 7 It was found that the binding energy of O2 on BN , VB , and VN defects is relatively large (1.6 - 3.1 eV), and it is unlikely that such configurations can be good precursors for catalytic reactions. However, in the case of NB defect the oxygen molecule is weakly bounded to the surface and strongly activated, similar to adsorption on Pt(111) surface. 7 Therefore, one can suggest that N doped monolayer h-BN can be a promising material with catalytic properties. Note, that doping of monolayer h-BN with N in B position is equivalent to a two electron doping changing electronic properties of h-BN from dielectric to n-type semiconductor. Let us now consider adsorption of O2 on a monolayer h-BN with CB , CN , and 2 CBN carbon defects. To obtain the most stable structures of O2 on the C doped h-BN monolayer, we have generated a large number of starting configuration by adding O2 with different orientation with respect to the surface, followed by the full structural optimization of the system. The similar approach has been successfully employed in our previous works to study adsorption and dissociation of various molecules on nanoclusters and surfaces. 7,9–11,27,59–62 As it was mentioned above, doping of monolayer h-BN with 2 carbon atoms in B and N positions, 2 CBN , results in appearance of the occupied states above the top of the valence band and the unoccupied states just below the bottom of the conduction band, however it does not change qualitatively the electronic properties of h-BN. Therefore it is likely, that 8 ACS Paragon Plus Environment

Page 8 of 28

Page 9 of 28

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


2 CBN @h-BN system remains inert for O2 adsorption. Indeed, out calculations demonstrate that O2 molecule weakly physisorbed on monolayer 2 CBN @h-BN in its triplet state and not activated, as shown in Figure 3a. The distance between O2 and 2 CBN @h-BN surface is about 3.1 ˚ A similar to the case of O2 adsorption on the pristine monolayer h-BN. Therefore, 2 CBN type of doping does not functionalize monolayer h-BN.

Figure 3: Optimized configurations of oxygen molecule adsorbed on monolayer h-BN doped with (a) two carbon atoms in B and N positions, 2 CBN ; (b) C atom in N position, CN ; and (c)-(e) C atom in B position CB . The interatomic distances are given in Angstroms. On the other hand, O2 can be effectively adsorbed on the CB @h-BN and CN @h-BN systems with a small band gap, where electrons can easily transfer between the adsorbate and the surface. Figure 3b demonstrate that in the case of CN impurity O2 adsorbs on top of C atom in the activated state, with the binding energy of 0.69 eV. Here, the binding energy of O2 molecule to the C doped h-BN surface is defined as Eb (O2 /C@h-BN) = E(C@h-BN) + E(O2 ) − E(O2 /C@h-BN),

(1)

where E(O2 /C@h-BN) is the total energy of the O2 /C@h-BN system, while E(C@h-BN) and E(O2 ) denote the total energies of the non-interacting free O2 and C doped h-BN surface, 9 ACS Paragon Plus Environment


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

respectively. A good catalyst for O2 activation should weaken O-O bond and bind O2 with the binding energy as small as possible, but large enough to prevent O2 from drifting away from the catalytic center. Therefore, CN @h-BN material can be considered as a good candidate for such catalyst. However, in the case of the CN doping O2 adsorbs only on the defect itself, therefore the number of the active sites is limited by the number of C atoms. The situation is principally different in the case of C doping in B position of monolayer h-BN: we have found several possible sites for O2 adsorption, as shown in Figures 3c-3e. The most stable configuration of O2 on CB @h-BN corresponds to the structure when O2 adsorbs on top of B atom closest to the CB defect (Figure 3c) with the binding energy of 1.45 eV. It is also possible that O2 adsorbs in a so-called bridge configuration, bridging two B atoms closest to the CB defect, or binding on top of C atom itself, as shown in Figures 3d and 3e, respectively. The calculated binding energies to O2 on CB @h-BN adsorbed in bridge and Ctop positions are 1.36 and 1.20 eV, respectively. In all considered cases the adsorbed oxygen molecule is highly activated, with the O-O bond length enlarged similar to the superoxide state O2 – . 63 Therefore, CB @h-BN can also function as a catalytic material for O2 activation and related reactions. However, the most interesting result is that in the case of CB @h-BN system, oxygen molecule readily adsorbs not only on top or in the close vicinity of the doped C atom as shown in Figures 3c-3e, but also far away from the CB defect. We have found that O2 adsorbs in the activated form in atop and bridge configurations at any B atoms in the considered 12x12 h-BN slab, with the binding energy slowly decreasing with increase in distance from the CB defect. No such effect is observed for the CN type of doping. Figure 4a presents the calculated binding energy of O2 adsorbed on CB @h-BN monolayer in top and bridge configurations as a function of distance RCB −B between the CB dopant and O2 adsorption site on the surface. As it was mentioned above, in the case of O2 adsorption on B atoms nearest to the CB dopant, the atop configuration (Figure 3c) is more favorable energetically if compared with the bridge one (Figure 3d); however, with increase in distance


Page 10 of 28

Page 11 of 28

RCB −B the bridge configuration becomes slightly more favorable. Overall, the binding energy of O2 varies from 1.45 eV to 0.1 eV for all considered adsorption sites on the CB @h-BN surface. This is very interesting result demonstrating that CB dopant functionalizes the large surface area around the defect where the adsorbed O2 can be activated. -0.6

(a)

1.4

Atop

(b)

Atop

Bridge

Bridge

Charge on O , |e|

1.2 1.0

-0.7

2

Binding Energy, eV

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


0.8 0.6 0.4

-0.8

-0.9

0.2

-1.0

0.0 0

2

4

6

R

,

CB-B

Å

8

10

12

0

2

4

6 R

,

CB-B

Å

8

10

12

Figure 4: The dependence of (a) the binding energy and (b) the Bader charge on the adsorbed O2 as a function of distance RCB −B between the CB dopant center and the active site for O2 adsorption on CB @h-BN. As it is known, adsorption of reactants on a catalytic surface should not be too strong in order to let reaction to proceed. The CB doping of monolayer h-BN provides a large variety of the adsorption sites where O2 can bind to the surface with the different binding energies depending on the distance from the defect. Therefore such material can automatically provide the most effective sites for O2 adsorption and activation with the optimal binding energy. It is interesting, that the Bader charge localized on the adsorbed O2 does not depend much on the distance RCB −B from the CB dopant changing in the range of -0.95e - -0.70e (Figure 4b), where e is an elementary charge. Therefore, the adsorbed O2 remains activated even far away from the C dopant. To gain more insight into the origin of O2 activation induced by the CB doping of monolayer h-BN we have calculated DOS projected on O and C atoms before and after O2 adsorption on CB @h-BN at different distances from the CB defect. Oxygen molecule possesses the occupied up-spin 2π ∗ orbital which is located below the Fermi level and the unoccupied 11 ACS Paragon Plus Environment


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

down-spin 2π ∗ orbital above the Fermi level, as shown in Figure 5a. Adsorption of O2 on CB @h-BN leads to the splitting of the up-spin 2π ∗ orbital of O2 due to interaction with the surface, population of the antibonding down-spin 2π ∗ orbital of O2 and de-population of the CB 2p defect level, as it is seen from Figures 5b - 5f. Such mechanism of the charge-transfermediated activation of O2 has been intensively studied for O2 adsorption on metal clusters and surfaces; see, e.g., refs. 7,10,30,59,64,65 and references therein. Figure 5b demonstrates that in the case of O2 adsorption on top of the CB dopant the C-2p defect level in the forbidden zone of h-BN disappears due to the strong mixing with O orbitals. However, when O2 adsorbs on B atoms in CB @h-BN one can clearly see an unoccupied C-2p defect level below the bottom of the BN conductivity band. It is seen from Figures 5c - 5f that position of the C-2p defect level shifts from the bottom of the conductivity band towards the Fermi level with increase in the distance RCB −B between the CB defect and O2 adsorption site. Nevertheless, even at the relatively large distances RCB −B = 11.8 ˚ A the occupied antibonding O2 -2π ∗ level is below the C-2p defect level, which explains the possibility of an electron transfer from CB to the adsorbed O2 . Figure 6 shows the isosurface of the electron density difference induced by the interaction of O2 molecule with the CB @h-BN surface at the distance of 11 ˚ A from the CB defect. As we have discussed above the charge transfer to the adsorbed O2 occurs from the p defect state induced by C dopant. It is seen from Figure 6 that the electron loss in the surface occurs mainly from the area which includes the C dopant and nearest N atoms due to the strong mixing of N-p and C-p orbitals. Finally, we would like to clarify the origin of the long range functionalization of the monolayer h-BN with CB defect, that allows adsorption and activation of oxygen molecule at the relatively long distances from the C dopant. For this purpose we have studied adsorption of O2 molecule on monolayer h-BN doped with group III, IV and V atoms B, C, N, Al, Si, Ge and transition-metal elements, Ni, Pt, Pd, and Au, both in B and N positions. In Table 1 we summarize the calculated maximum distance Rmax from the defect site to


Page 12 of 28

Page 13 of 28

6 (a)

6

h

O +C @ -BN 2

B

4 O -1 BN-2p

O -2 2

O -5 2

BN-2p

2

-1

0 -2

B

C-2p

PDOS, eV

-1

2

4

2

2

PDOS, eV

(b) O /C @h-BN

O -2

2

0 C-2p

-2

-4

-4

O -2

O -2

O -1

2

2

2

-6 -10

-5

0

-6 -10

5

-5

Energy, eV

2

(d) O /C @h-BN

B

4

2

B

O -2

4

O -2 2

C-2p

BN-2p

PDOS, eV

0 -2

2

C-2p

BN-2p

2

-1

2

-1

5

6 (c) O /C @h-BN

PDOS, eV

0 Energy, eV

6

0 -2 O -2 2

-4

-4

O -2 2

-6 -10

-5

0

-6 -10

5

-5

Energy, eV

5

6 (e) O /C @h-BN 2

2

O -2

B

O -2

4

2

C-2p -1

BN-2p

PDOS, eV

2

(f) O /C @h-BN

B

4

-1

0 Energy, eV

6

PDOS, eV

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


0 -2

2

2

BN-2p

0 -2

O -2

O -2

2

-4 -6 -10

C-2p

2

-4

-5

0

-6 -10

5

Energy, eV

-5

0

5

Energy, eV

Figure 5: Partial density of electronic states (PDOS) projected on B and N (black dotted line), C (red dashed line), and O (blue solid line) atoms calculated for (a) free O2 molecule and CB @h-BN, (b) O2 adsorbed on top of C atom, and O2 adsorbed on B atoms of CB @h-BN at the different distances between the CB dopant center and O2 adsorption site: (c) RCB −B = 2.5 ˚ A, (d) RCB −B = 4.7 ˚ A, (e) RCB −B = 7.0 ˚ A, (f) RCB −B = 11.8 ˚ A. The Fermi level is indicated by a dashed vertical line at 0 eV, arrows directed up and down indicate the up spin and down spin PDOS, PDOS of h-BN is normalized by the number of BN pairs in the slab multiplied by 5. A Gaussian broadening of half-width 0.05 eV has been used. 13 ACS Paragon Plus Environment


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

Page 14 of 28

eO2

CB

Figure 6: Isosurface of the electron density difference induced by interaction of O2 molecule with the CB @h-BN surface, i.e. ρtot (O2 /CB @h-BN) − ρtot (O2 ) − ρtot (CB @h-BN). Yellow regions correspond to excess electronic charge and green ones correspond to the electron loss. The contours shown are at +0.006 and -0.006 electrons per ˚ A3 .

Table 1: The energy difference between the highest occupied defect level and the bottom of the conduction band, ε1 , the lowest unoccupied defect level and the top of the valence band, ε2 , and the maximum distance from the defect site to the adsorption site where O2 can still be adsorbed, Rmax , calculated for the different type of defects in monolayer h-BN. Dopant ε1 , eV CB NB AlB SiB GeB NiB PdB PtB AuB

0.94 3.09 3.96 3.11 3.83 4.21 3.25 2.77 3.81

ε2 , eV Rmax , ˚ A Dopant ε1 , eV 3.85 4.43 3.96 2.68 1.34 0.50 1.26 1.30 1.09

∼ 12 2.43 0.00 0.00 0.00 0.00 0.00 0.00 0.00

CN BN AlN SiN GeN NiN PdN PtN AuN

4.05 3.96 2.62 3.76 3.42 1.93 1.42 1.51 3.22


ε2 , eV

Rmax , ˚ A

0.85 1.88 2.68 1.38 1.44 3.56 2.77 2.68 3.72

0.00 0.00 0.00 0.00 0.00 6.56 6.56 6.56 0.00

Page 15 of 28

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


the adsorption site on monolayer h-BN surface where O2 molecule can still be adsorbed and activated. Here Rmax = 0 denotes direct adsorption on the dopant. We consider doping of monolayer h-BN with several different atoms of group III, IV and V and transition-metal elements such as B, N, Al, Si, Ge, Ni, Pt, Pd, and Au, that can play a role of n- or p-type of dopants. It is seen from Table 1 that in most of the considered cases O2 adsorbs directly on top of the dopant atom, with the exception of CB , where the active area around the defect is at least 12 ˚ A. O2 can also be activated in a close vicinity of the NB , as well as at distances up to 6.6 ˚ A from NiN , PdN , and PtN defects. In order to understand such a behavior we have performed analysis of the electronic structure of monolayer h-BN doped with the defects listed in Table 1. As it was discussed above activation of the adsorbed molecular oxygen occurs as a result of electron transfer to the unoccupied 2π ∗ antibonding orbital, which is located close to the Fermi level and the bottom of the conduction band of h-BN, as it is seen from Figure 5a. Therefore, if the occupied defect level approaches the bottom of the conduction band the system becomes effective n-type semiconductor and an electron transfer from the defect to the oxygen molecule O2 occurs even at the large distances from the defect. To illustrate this effect we have calculated the energy gap, ε1 , between the highest occupied defect level and the bottom of the conduction band of the monolayer h-BN doped with B, C, N, Al, Si, Ge, Ni, Pt, Pd, and Au atoms. As it it seen from the Table 1 the occupied C-2p defect level of CB is located close to the bottom of the conduction band of h-BN, ε1 =0.94 eV indicating that CB monolayer h-BN has an electronic structure of a typical n-type semiconductor. It is important to note that experimentally was demonstrated transformation of BN nanotubes from electrical insulators to conductors upon substitutional C doping. 31 In the case of NiN , PdN , and PtN dopant defects in monolayer h-BN the calculated gaps between the highest occupied defect level and the bottom of the conduction band are 2.00 eV, 1.89 eV and 1.93 eV, respectively, resulting in functionalization of the area with the radius of 6.6 ˚ A. For other considered cases of dopants the highest occupied defect level lies considerably deeper in respect to the bottom of conduction band and O2 adsorbs only



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

Page 16 of 28

on the defect atom itself or in its close vicinity. Therefore to functionalize the large area of monolayer h-BN by atomic doping for oxygen activation one should introduce defect states as close as possible to the bottom of the conduction band. On the other hand, one can suggest that in the case of p-type doped monolayer h-BN adsorption of the electron donor type of molecules can occur effectively. As it is seen from Table 1 CN and NiB are promising dopants for such materials.

CB @h-BN as an electrocatalyst for oxygen reduction reaction In order to demonstrate a high potential of C doped BN based nanosystems for catalytic applications we consider possibility of the oxygen reduction reaction on CB @h-BN. Oxygen reduction reaction is one of the most important catalytic processes in a fuel cell technology. The overall ORR can be written in the following simple form: O2 + 4H+ + 4e− → 2H2 O.

(2)

A simple description of the ORR mechanism includes investigation on the adsorption preferences of O2 , OOH, O, and OH intermediates on a model catalyst and analysis of the overall energetics of the ORR process along the possible reaction pathways. Such simplified approach has been introduced by Nørskov 66 and described in details by Keith and Jacob. 67–69 It has been demonstrated that such an approach allows one to introduce a simplified model for the electrode kinetics and reveal the origin of the overpotential for ORR consistent with experiment. 66 In our previous works we have used similar approach to study of ORR on a number of BN based systems, including the N-doped h-BN monolayer, 7 h-BN monolayer deposited on a Ni(111) 8 and Au(111) 9 supports. Experimental proofs of electrocatalytic activity of the functionalized BN based nanosystems have also been reported. 9,70 In the present work we analyze the change in the heats of formation, ∆Hf , during the reaction. Calculations details are described previously. 7–9 In order to simplify the description


Page 17 of 28

in the present work we do not take into account the change in entropy during the reaction, zero point energy (ZPE) corrections and the effect of solvent (water) environment on the ORR process. We have demonstrated that such corrections partly cancel each other and have to be taken into account or neglected simultaneously. 7 Therefore, the uncorrected heats of formation can be considered as a good initial approximation for a simple analysis of the ORR energetics. A systematic description of ORR on CB @h-BN accounting for entropy effects, ZPE and solvent corrections goes far beyond the aims of the present study and will be presented in full elsewhere. 1 2H , O

0

2

2H , O *

2

2

2

3/2H

2

OOH*

-1

H

2

H O 2

O*, H O

2

2

-2 -3

1/2H

2

f

H , eV

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


-4 -5

OH*, H O 2

C

B

R

C -B

= 2.5 Å

2H O

B

R

C -B

2

= 7.5 Å

B

-6

R

C -B

= 11.5 Å

B

-7 Reaction Coordinate

Figure 7: Energy diagram for ORR on CB @h-BN at different distances from the CB dopant. Figure 7 presents the energy diagrams calculated for the ORR on CB @h-BN. Heats of formation, ∆Hf , without ZPE and solvent corrections are calculated for ORR on top of C dopant (black doted lines), and active sites located at the RCB −B distances of 2.5 ˚ A (red solid lines), 7.5 ˚ A (green dashed lines), and 11.5 ˚ A (blue dashed-dotted lines) from the CB dopant. It is seen from Figure 7 that in the case of ORR on top of C dopant or in its close vicinity ∆Hf goes downhill until formation of OH* on CB @h-BN, while the further reduction of OH* to H2 O is slightly unfavorable energetically as a result of a strong OH* binding to CB @h-BN. However, accounting for entropy, zero-point energy and solvent effects can make the last step of the ORR process to be energetically favorable, due to the fact, that 17 ACS Paragon Plus Environment


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

the final product of the reaction, H2 O, does not bind to the surface, and hence its entropy is not zero. 7 On the other hand, at the large distances from the C dopant binding of ORR intermediates to CB @h-BN become weaker, and all process along the reaction pathway goes downhill. Thus, we have demonstrated that CB @h-BN provides a variety of active sites for ORR in the large area around the CB dopant. The detailed analysis on energetics of ORR on C doped monolayer h-BN will be presented elsewhere.

Conclusions In summary, we present theoretical study on functionalization of monolayer BN by atomic doping for oxygen activation. It is demonstrated that C doping in B position of h-BN produces n-type semiconductor BN material with noticeable catalytic activity for O2 activation in the large area extended far away from the C impurity. The binding energy of O2 to monolayer h-BN functionalized by CB type of dopant decreasing slowly with the increase in distance from the C impurity, while O2 remains highly activated. Such catalytic activation of the adsorbed oxygen is deduced as a result of electron transfer from the occupied defect level introduced by CB impurity to the 2π ∗ antibonding orbital of O2 . Small energy gap between the occupied defect level and the bottom of the conduction band leads to functionalization of the large area around the defect. Therefore to design effective BN based catalyst using atomic doping one should introduce occupied defect states in a close vicinity of the bottom of the conduction band. Finally, we would like to note that the CB doping of monolayer h-BN provides a large variety of possible adsorption sites where the binding energy of O2 to the surface can be controlled by the distance from the defect site. Based on the simple energy analysis, we have demonstrated that CB @h-BN system can play a role of the catalyst for ORR with the large active area. Such effect can open new ways for tailored design of novel catalysts with tunable properties based on abundant materials.


Page 18 of 28

Page 19 of 28

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


Acknowledgement This work was supported by the Japan Society for the Promotion of Science (JSPS KAKENHI Grants 15K05387 and 26288001), the FLAGSHIP2020 program supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan within the priority study5 (Development of new fundamental technologies for high-efficiency energy creation, conversion/storage and use), partially supported by the Development of Environmental Technology using Nanotechnology (MEXT) and partly performed under the management of the ”Elements Strategy Initiative for Catalysts and Batteries (ESICB)” supported by MEXT program ”Elements Strategy Initiative to Form Core Research Center” (since 2012). The computations were partly performed at the Research Center for Computational Science, Okazaki, Japan.

Supporting Information Available The overall total DOS the pristine and carbon doped monolayer h-BN. This material is available free of charge via the Internet at http://pubs.acs.org/.

References (1) Haruta, M. Gold Rush. Nature 2005, 437, 1098–1099. (2) Hughes, M. D.; Xu, Y.-J.; Jenkins, P.; McMorn, P.; Landon, P.; Enache, D. I.; Carley, A. F.; Attard, G. A.; Hutchings, G. J.; King, F. et al. Tunable Gold Catalysts for Selective Hydrocarbon Oxidation under Mild Conditions. Nature 2005, 437, 1132–1135. (3) Turner, M.; Golovko, V. B.; Vaughan, O. P. H.; Abdulkin, P.; Berenguer-Murcia, A.; Tikhov, M. S.; Johnson, B. F. G.; Lambert, R. M. Selective Oxidation with Dioxygen



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

by Gold Nanoparticle Catalysts Derived from 55-Atom Clusters. Nature 2008, 454, 981–984. (4) Davis, S. E.; Ide, M. S.; Davis, R. J. Selective Oxidation of Alcohols and Aldehydes over Supported Metal Nanoparticles. Green Chem. 2013, 15, 17–45. (5) Chen, Z.; Dodelet, J.; J., Z. Non-Noble Metal Fuel Cell Catalysts; WILEY-VCH Verlag, 2014. (6) Marković, N. M.; Schmidt, T. J.; Stamenković, V.; Ross, P. N. Oxygen Reduction Reaction on Pt and Pt Bimetallic Surfaces: A Selective Review. Fuel Cells 2001, 1, 105–116. (7) Lyalin, A.; Nakayama, A.; Uosaki, K.; Taketsugu, T. Theoretical Predictions for Hexagonal BN Based Nanomaterials as Electrocatalysts for the Oxygen Reduction Reaction. Phys. Chem. Chem. Phys. 2013, 15, 2809–2820. (8) Lyalin, A.; Nakayama, A.; Uosaki, K.; Taketsugu, T. Functionalization of Monolayer h-BN by a Metal Support for the Oxygen Reduction Reaction. J. Phys. Chem. C 2013, 117, 21359–21370. (9) Uosaki, K.; Elumalai, G.; Noguchi, H.; Masuda, T.; Lyalin, A.; Nakayama, A.; Taketsugu, T. Boron Nitride Nanosheet on Gold as an Electrocatalyst for Oxygen Reduction Reaction: Theoretical Suggestion and Experimental Proof. J. Am. Chem. Soc. 2014, 136, 6542–6545. (10) Gao, M.; Lyalin, A.; Taketsugu, T. Role of the Support Effects on the Catalytic Activity of Gold Clusters: A Density Functional Theory Study. Catalysts 2011, 1, 18–39. (11) Gao, M.; Lyalin, A.; Taketsugu, T. Catalytic Activity of Au and Au2 on h-BN Surface: Adsorption and Activation of O2 . J. Phys. Chem. C 2012, 116, 9054–9062.


Page 20 of 28

Page 21 of 28

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


(12) Gao, M.; Lyalin, A.; Taketsugu, T. Oxygen Activation and Dissociation on h-BN Supported Au Atoms. Int. J. Quantum Chem. 2013, 113, 443–452. (13) Gao, M.; Lyalin, A.; Taketsugu, T. CO Oxidation on h-BN Supported Au Atom. J. Chem. Phys. 2013, 138, 034701. (14) Zhao, P.; Su, Y.; Zhang, Y.; Li, S.-J.; Chen, G. CO Catalytic Oxidation on IronEmbedded Hexagonal Boron Nitride Sheet. Chem. Phys. Lett. 2011, 515, 159 – 162. (15) Lin, S.; Ye, X.; Johnson, R. S.; Guo, H. First-Principles Investigations of Metal (Cu, Ag, Au, Pt, Rh, Pd, Fe, Co, and Ir) Doped Hexagonal Boron Nitride Nanosheets: Stability and Catalysis of CO Oxidation. J. Phys. Chem. C 2013, 117, 17319–17326. (16) Ci, L.; Song, L.; Jin, C.; Jariwala, D.; Wu, D.; Li, Y.; Srivastava, A.; Wang, Z. F.; Storr, K.; Balicas, L. et al. Atomic Layers of Hybridized Boron Nitride and Graphene Domains. Nat Mater 2010, 9, 430–435. (17) Zhou, J.; Wang, Q.; Sun, Q.; Jena, P. Electronic and Magnetic Properties of a BN Sheet Decorated with Hydrogen and Fluorine. Phys. Rev. B 2010, 81, 085442. (18) Azevedo, S.; Kaschny, J. Hydrogenated BN Monolayers: A First Principles Study. The European Physical Journal B 2013, 86 . (19) Rokuta, E.; Hasegawa, Y.; Suzuki, K.; Gamou, Y.; Oshima, C.; Nagashima, A. Phonon Dispersion of an Epitaxial Monolayer Film of Hexagonal Boron Nitride on Ni(111). Phys. Rev. Lett. 1997, 79, 4609–4612. (20) Huda, M. N.; Kleinman, L. h-BN Monolayer Adsorption on the Ni(111) Surface: A Density Functional Study. Phys. Rev. B 2006, 74, 075418. (21) Preobrajenski, A. B.; Vinogradov, A. S.; M˚ artensson, N. Ni 3d-BN π Hybridization at the h-BN/Ni(111) Interface Observed with Core-Level Spectroscopies. Phys. Rev. B 2004, 70, 165404. 21 ACS Paragon Plus Environment


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

(22) Preobrajenski, A. B.; Vinogradov, A. S.; M˚ artensson, N. Monolayer of h-BN Chemisorbed on Cu(111) and Ni(111): The Role of the Transition Metal 3d States. Surf. Sci. 2005, 582, 21–30. (23) Preobrajenski, A. B.; Krasnikov, S. A.; Vinogradov, A. S.; Ng, M. L.; Käa¨mbre, T.; Cafolla, A. A.; M˚ artensson, N. Adsorption-Induced Gap States of h-BN on Metal Surfaces. Phys. Rev. B 2008, 77, 085421. (24) Laskowski, R.; Blaha, P.; Schwarz, K. Bonding of Hexagonal BN to Transition Metal Surfaces: An ab initio Density-Functional Theory Study. Phys. Rev. B 2008, 78, 045409/1–10. (25) Oshima, C.; Itoh, A.; Rokuta, E.; Tanaka, T.; Yamashita, K.; Sakurai, T. HeteroEpitaxial-Double-Atomic-Layer System of Monolayer Graphene/Monolayer h-BN on Ni(111). Solid State Commun 2000, 116, 37–40. (26) Wasey, A. H. M. A.; Chakrabarty, S.; Das, G. P.; Majumder, C. h-BN Monolayer on the Ni(111) Surface: A Potential Catalyst for Oxidation. ACS Applied Materials & Interfaces 2013, 5, 10404–10408. (27) Lyalin, A.; Nakayama, A.; Uosaki, K.; Taketsugu, T. Adsorption and Catalytic Activation of the Molecular Oxygen on the Metal Supported h-BN. Top. Catal. 2014, 57, 1032–1041. (28) Koitz, R.; Norskov, J. K.; Studt, F. A Systematic Study of Metal-Supported Boron Nitride Materials for the Oxygen Reduction Reaction. Phys. Chem. Chem. Phys. 2015, 17, 12722–12727. (29) Sinthika, S.; Kumar, E. M.; Thapa, R. Doped h-BN Monolayer as Efficient Noble Metal-Free Catalysts for CO Oxidation: the Role of Dopant and Water in Activity and Catalytic De-poisoning. J. Mater. Chem. A 2014, 2, 12812–12820.


Page 22 of 28

Page 23 of 28

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


(30) Shin, D.; Thapa, R.; Park, N. An Oxygen Reduction Catalytic Process through Superoxo Adsorption States on n-type Doped h-BN: A First-Principles Study. Current Applied Physics 2015, 15, 727 – 732. (31) Wei, X.; Wang, M.-S.; Bando, Y.; Golberg, D. Post-Synthesis Carbon Doping of Individual Multiwalled Boron Nitride Nanotubes via Electron-Beam Irradiation. J. Am. Chem. Soc. 2010, 132, 13592–13593. (32) Wei, X.; Wang, M.-S.; Bando, Y.; Golberg, D. Electron-Beam-Induced Substitutional Carbon Doping of Boron Nitride Nanosheets, Nanoribbons, and Nanotubes. ACS Nano 2011, 5, 2916–2922. (33) Krivanek, O. L.; Chisholm, M. F.; Nicolosi, V.; Pennycook, T. J.; Corbin, G. J.; Dellby, N.; Murfitt, M. F.; Own, C. S.; Szilagyi, Z. S.; Oxley, M. P. et al. Atom-by-Atom Structural and Chemical Analysis by Annular Dark-Field Electron Microscopy. Nature 2010, 464, 571–574. (34) Berseneva, N.; Krasheninnikov, A. V.; Nieminen, R. M. Mechanisms of Postsynthesis Doping of Boron Nitride Nanostructures with Carbon from First-Principles Simulations. Phys. Rev. Lett. 2011, 107, 035501. (35) Berseneva, N.; Gulans, A.; Krasheninnikov, A. V.; Nieminen, R. M. Electronic Structure of Boron Nitride Sheets Doped with Carbon from First-Principles Calculations. Phys. Rev. B 2013, 87, 035404. (36) Huang, C.; Chen, C.; Zhang, M.; Lin, L.; Ye, X.; Lin, S.; Antonietti, M.; Wang, X. Carbon-Doped BN Nanosheets for Metal-Free Photoredox Catalysis. Nat Commun 2015, 6 . (37) Wu, Z.; Cohen, R. E. More Accurate Generalized Gradient Approximation for Solids. Phys. Rev. B 2006, 73, 235116/1–6.



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

(38) Sánchez-Portal, D.; Ordejón, P.; Artacho, E.; Soler, J. M. Density-Functional Method for Very Large Systems with LCAO Basis Sets. Int. J. Quantum Chem. 1997, 65, 453–461. (39) Soler, J. M.; Artacho, E.; Gale, J. D.; Garc´ıa, A.; Junquera, J.; Ordejón, P.; SánchezPortal, D. The Siesta Method for ab initio Order-N Materials Simulation. J. Phys.: Condens. Matter 2002, 14, 2745–2779. (40) Sánchez-Portal, D.; Ordejón, P.; Canadell, E. Computing the Properties of Materials from First Principles with Siesta. Structure and Bonding 2004, 113, 103–170. (41) Artacho, E.; Sánchez-Portal, D.; Ordejón, P.; Garc´ıa, A.; Soler, J. M. Linear-Scaling ab-initio Calculations for Large and Complex Systems. Phys. Stat. Sol. (b) 1999, 215, 809–817. (42) Junquera, J.; Paz, O.; Sánchez-Portal, D.; Artacho, E. Numerical Atomic Orbitals for Linear-Scaling Calculations. Phys. Rev. B 2001, 64, 235111/1–9. (43) Troullier, N.; Martins, J. L. Efficient Pseudopotentials for Plane-Wave Calculations. Phys. Rev. B 1991, 43, 1993–2006. (44) Kleinman, L.; Bylander, D. M. Efficacious Form for Model Pseudopotentials. Phys. Rev. Lett. 1982, 48, 1425–1428. (45) Monkhorst, H. J.; Pack, J. D. Special Points for Brillouin-Zone Integrations. Phys. Rev. B 1976, 13, 5188. (46) Yoo, C. S.; Akella, J.; Cynn, H.; Nicol, M. Direct Elementary Reactions of Boron and Nitrogen at High Pressures and Temperatures. Phys. Rev. B 1997, 56, 140–146. (47) Huber, K. P.; Herzberg, G. Molecular Spectra and Molecular Structure Constants of Diatomic Molecules; Van Nostrand Reinhold: New York, 1979.


Page 24 of 28

Page 25 of 28

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


(48) Bader, R. Atoms in Molecules: A Quantum Theory; Oxford University Press, New York, 1990. (49) Henkelman, G.; Arnaldsson, A.; Jónsson, H. A Fast and Robust Algorithm for Bader Decomposition of Charge Density. Comput. Mater. Sci. 2006, 36, 354–360. (50) Tang, W.; Sanville, E.; Henkelman, G. A Grid-Based Bader Analysis Algorithm without Lattice Bias. Journal of Physics: Condensed Matter 2009, 21, 084204. (51) Kokalj, A. Computer Graphics and Graphical user Interfaces as Tools in Simulations of Matter at the Atomic Scale. Comp. Mat. Sci. 2003, 28, 155–168. (52) Azevedo, S.; Kaschny, J. R.; de Castilho, C. M.; de Brito Mota, F. Electronic Structure of Defects in a Boron Nitride Monolayer. Eur. Phys. J. B 2009, 67, 507–512. (53) Solozhenko, V.; Lazarenko, A.; Petitet, J.-P.; Kanaev, A. Bandgap Energy of GraphiteLike Hexagonal Boron Nitride. J. Phys. Chem. Solids 2001, 62, 1331 – 1334. (54) Blase, X.; Rubio, A.; Louie, S. G.; Cohen, M. L. Quasiparticle Band Structure of Bulk Hexagonal Boron Nitride and Related Systems. Phys. Rev. B 1995, 51, 6868–6875. (55) Liu, L.; Feng, Y. P.; Shen, Z. X. Structural and Electronic Properties of h-BN. Phys. Rev. B 2003, 68, 104102. (56) Topsakal, M.; Akt¨ urk, E.; Ciraci, S. First-Principles Study of Two- and OneDimensional Honeycomb Structures of Boron Nitride. Phys. Rev. B 2009, 79, 115442. (57) S¸ahin, H.; Cahangirov, S.; Topsakal, M.; Bekaroglu, E.; Akturk, E.; Senger, R. T.; Ciraci, S. Monolayer Honeycomb Structures of Group-IV Elements and III-V Binary Compounds: First-Principles Calculations. Phys. Rev. B 2009, 80, 155453. (58) Shishkin, M.; Marsman, M.; Kresse, G. Accurate Quasiparticle Spectra from SelfConsistent GW Calculations with Vertex Corrections. Phys. Rev. Lett. 2007, 99, 246403. 25 ACS Paragon Plus Environment


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

(59) Lyalin, A.; Taketsugu, T. Cooperative Adsorption of O2 and C2 H4 on Small Gold Clusters. J. Phys. Chem. C 2009, 113, 12930–12934. (60) Lyalin, A.; Taketsugu, T. Adsorption of Ethylene on Neutral, Anionic, and Cationic Gold Clusters. J. Phys. Chem. C 2010, 114, 2484–2493. (61) Lyalin, A.; Taketsugu, T. Reactant-Promoted Oxygen Dissociation on Gold Clusters. J. Phys. Chem. Lett. 2010, 1, 1752–1757. (62) Lyalin, A.; Taketsugu, T. A Computational Investigation of H2 Adsorption and Dissociation on Au Nanoparticles Supported on TiO2 Surface. Faraday Discuss. 2011, 152, 185–201. (63) Wiberg, N., Holleman, A. F., Wiberg, E., Eds. Inorganic Chemistry; Academic Press, 2001. (64) Häkkinen, H.; Landman, U. Gas-Phase Catalytic Oxidation of CO by Au2 – . J. Am. Chem. Soc. 2001, 123, 9704–9705. (65) Yoon, B.; Häkkinen, H.; Landman, U. Interaction of O2 with Gold Clusters: Molecular and Dissociative Adsorption. J. Phys. Chem. A 2003, 107, 4066–4071. (66) Nørskov, J. K.; Rossmeisl, J.; Logadottir, A.; Lindqvist, L.; Kitchin, J. R.; Bligaard, T.; Jónsson, H. Origin of the Overpotential for Oxygen Reduction at a Fuel-Cell Cathode. J. Phys. Chem. B 2004, 108, 17886–17892. (67) Jacob, T. The Mechanism of Forming H2 O from H2 and O2 over a Pt Catalist via Direct Oxigen Reduction. Fuel Cells 2006, 06, 159–181. (68) Keith, J. A.; Jerkiewicz, G.; Jacob, T. Theoretical Investigations of the Oxygen Reduction Reaction on Pt(111). ChemPhysChem 2010, 11, 2779–2794.


Page 26 of 28

Page 27 of 28

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


(69) Keith, J. A.; Jacob, T. Theoretical Studies of Potential-Dependent and Competing Mechanisms of the Electrocatalytic Oxygen Reduction Reaction on Pt(111). Angew. Chem. Int. Ed. 2010, 49, 9521–9525. (70) Elumalai, G.; Noguchi, H.; Uosaki, K. Electrocatalytic activity of various types of h-BN for the oxygen reduction reaction. Phys. Chem. Chem. Phys. 2014, 16, 13755–13761.



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

Graphical TOC Entry


Page 28 of 28

Long Range Functionalization of h-BN Monolayer by Carbon Doping

Recommend Documents