Embed Size (px)
Citation preview
Atomic hydrogen adsorption behavior of boron nitride nanomaterial
Outline
1. Introduction
2. Sample preparation & Deuteration.
3. TOF
4. NEXAFS- Experiment & Calculation.
5. XPS-Experiment & Calculation.
6. PSID.
7. Why H/D prefers to adsorb on B site ?
Kaveenga Rasika Koswattage (PhD) Senior Lecture
Faculty of Applied Science,
Sabaragamuwa University
1
Transportation Fuel cell power technology Renewable
Sustainable
Light-duty vehicles
Light storage system
Introduction
CNT BNNT
US DOE on board hydrogen system has proposed to achieve 5 wt % hydrogen storage by
Introduction
C-H
Hydrogenation degree
= 0.370.05
A. Nikitin et al., Surf. Sci. 602,
2575 (2008).
C 1s XPS
Bending of C–H
bonds
H adsorbed on
neighbor carbon
Hydrogen adsorption on BN is site selective
H
B N
Wu et al., J. Chem. Phys.
121, 8481 (2003).
V.A Margulis et al.,
springer , 275 (2007).
Graphite
Hydrogenation on BNNT > CNT Ex: R. Ma et al., J. Am. Chem.
Soc. 124 , 7672 (2002).
H atom prefers
to adsorb on the
top site of the B
H atom prefers
to adsorb on the
top site of the N
Two hydrogen atoms adsorbed on-top sites
of adjacent B and N atoms Z. Zhou et al., J. Phys. Chem. B
110, 13363 (2002).
Hydrogenation was examined using thin film of h-BN 3
Ni(111)
substrate
·lattice constant
·atomic distance
lattice
matching
h-BN 2.51 Å
Ni(111) 2.49Å -0.4 %
Pd(111) 2.76Å 10 %
Pt(111) 2.89Å 15.2 %
Borazine
(B3N3H6)
N N B
B B
H
H H
H
H
H N
Ni(111) ~800 ℃
Precursor gas Nagashima et al., Phys.
Rev. B 51, 4606 (1995).
BN film on Ni(111) substrate
Chemical Vapor Deposition
Thin film of h-BN on a Ni(111) substrate was selected for the investigation
W. Auwarter et al., Surf. Sci.,
429, 229 (1999). h-BN on a Ni(111)
Well ordered Highly commensurate Perfect lattice match
C 1s VB
0 100 200 300 400 500
0
500
1000
1500
2000
Inte
nsi
ty /
cps
Binding Energy / eV
Ni 3s
Ni 3p
B 1s
N KLL Auger
N 1s
B KLL Auger
hν = 695 eV
Fig. XPS after formation of BN film on Ni(111)
Thickness of the BN film was estimated to be 6.6 Å 4
5
Photon Factory- High Energy Accelerator Research Organization (KEK), Japan
Experiment using Synchrotron Radiation
Beam line 11-A
F
BK EhE
X-ray Photoelectron spectroscopy (XPS)
(a). XPS spectra of clean HOPG
(b). H treated HOPG with H saturated coverage
A. Nikitin et al., Surf. Sci. 602, 2575 (2008).
(a)clean HOPG
(b).H treated
HOPG
6
180 188 196 204 212 220 228
Vacuum
*
Core level
σ*
Unoccupied
levels
Excitation
Energy
Photon Energy / eV
Ab
sorp
tion I
nte
nsi
ty
Synchrotron
Radiation
*
σ*
Photon Energy (eV)
Ab
sorp
tion
in
ten
sity
(ar
b. un
its.
)
NEXAFS
σ*
*
(a) (b)
Continuum States
Eπ*
Eσ*
IP
IP
FL
ValenceBand σ*
(b). A typical B – Kedge NEXAFS spectrum of
bulk h-BN which shows two features, π* and σ*.
(a). Schematic representation of the processes involved in NEXAFS for unsaturated
compounds with double or triple bonds.
Near-edge X-ray absorption fine structure (NEXAFS)
I. Shimoyama et al., J. Elec. Spec. Relat. Phenom.
137, 573 (2004).
7
Grazing incidence ： Enhancement of 1s *
Normal incidence ： Enhancement of 1s σ *
E
G razing
incidence
N ormal
incidence
N
G
* s *
O
O s
E
π orbital
σ orbital
E
sp2
θ=20º
θ=90º
Polarization dependence -NEXAFS
C K-edge NEXAFS spectra of single-crystal
graphite at various incident angles (θ )
R.A. Rosenberg et al., Phys.
Rev. B 33, 4034 (1986).
8
② NEXAFS
Au mesh
試 I(h)
①XPS
I0 (h)
Synchrotron
radiation ring
A
A
hν=700 eV
Hot filament system
X-ray gun
QMS
Analyzer
Ion gun
Hot
filament
system
Ultra high vacuum chamber
Base pressure of the UHV chamber was ~8×10-8 Pa
Experimental
I(h)
I0 (h)
All the experiments were
performed at the BL-11A beam
line of the Photon Factory. BN/Ni(111)
07.0 A
10.0 V 9
NEXAFS -Spectral change by atomic deuterium treatment
400 410 420 430 440In
ten
sity
(arb
. u
nit
)
N K-edge
Photon Energy / eV
Before
After
188 192 196 200 204
Inte
nsi
ty (
arb
. u
nit
)
B K-edge
Photon Energy / eV
π*B
π*A σ* Before
After
Experimental results-NEXAFS
Interaction change between
film and substrate by
deuterium adsorption
1.Formation of B-D bond or
2. Interaction change between film and
substrate by deuterium adsorption or
3.Resultant of these two phenomena. 10
Spectral change between π*A
and σ*showing similar
polarization dependence like
π*A & π*B .
185 190 195 200 205 210
Inte
nsit
y (
arb
. u
ni )
Photon Energy / eV
angle ( ) = 20
angle ( ) = 35
angle ( ) = 55
B
D
Out of plane orientation – B-D bonds are perpendicular to the surface
Out of plane orientation was used for DV-Xα calculation
Spectral change between π*A & σ*
Formation of B-D bond
E SR
Polarization dependence NEXAFS
Before
After
Before
After
Before
After
B K-edge
11
BN film- B27N27H18
Unoccupied
states
Vacuum
π*
σ* 0.5
0.5
One H on B site
One H on N site
Two H on adjacent B&N site
DV-Xα Calculation
Slater’s transition theory
☆Minimal basis set :
•2s & 2p for B&N
•1s for H
▲Model clusters :
optimization :
Win MOPAC / AM1
Model clusters Calculation method
B
N
H
( A molecular orbital calculation method)
12
1. One H attached to B site
DV-Xα Calculation- NEXAFS
B 1s to LUMO
π* σ*
B-Without H
B-With H
13
N-With H
N-Without H
2. One H attached to N site N 1s to LUMO
π* σ*
DV-Xα Calculation- NEXAFS
14
XPS-Spectral change by atomic deuterium treatment
188 190 192 1940
1
2
3
4
Inte
nsi
ty (
arb
. u
nit
)
Binding Energy / eV
Additional component appeared at low BE
Before
After
B 1s
396 398 400 4020
1
2
3
Inte
nsi
ty (
arb
. u
nit
)
Binding Energy / eV
Broadening to high BE
Before
After
N 1s
Experimental results-XPS
15
188 190 192 1940
1
2
3
4
Inte
nsi
ty (
arb
. u
nit
)
Binding Energy / eV
Before
After
B 1s
396 398 400 4020
1
2
3
Inte
nsi
ty (
arb
. u
nit
)
Binding Energy / eV
Before
After
N 1s
XPS calculation
XPS-Spectral change by atomic deuterium treatment
Cluster
Chemical shift ( eV)
Hydrogenated sites Neighboring sites
B 1s N 1s B 1s N 1s
B27N27H18+HB -0.7 N/A N/A -0.4
B27N27H18+HN N/A +2.2 -2.0 N/A
B27N27H18+2HBN -1.6 +2.2 N/A N/A
DV-Xα Calculation- XPS
B-D
16
187 188 189 190 191 192 193 194 195
Binding Energy / eV
Inte
nsit
y (
arb
. u
ni )
BD
A
A* Rtop
Degree of deuteration was estimated to be 29 % considering only B site.
NEXAFS and XPS results imply that atomic deuterium adsorption
occurred on B site more preferentially than on N site
,100 topD
D
RAB
B
Degree of deuteration (%) =
Degree of deuteration
17
Deuterium ion
X-ray
（N excitation）
X-ray
（B excitation）
Why PSID ?
NEXAFS and XPS spectroscopic methods are not considered to
be methods of directly detecting hydrogen from the surface
Photon stimulated ion desorption ( PSID)
PSID can be employed to study hydrogen adsorption sites on a BN film
Time of flight mass spectrometer
18
PSID yield () spectra for D+ ion
Clear increase at the B
K-edge
0
40
80
120
160
184 188 192 196
395 400 405 410
B
Photon Energy / eV
N
D+
des
orp
tio
n y
ield
(
arb
. u
nit
)
Electron excited to
* state
B-D anti bonding
state
does not show clear increase in the N K-edge
N sites adsorbed by deuterium was smaller than B 19
Why H/D prefers to adsorb on B site ??
Explanation is based on the frontier orbital theory
0.00
0.05
0.10
0.15
0.20
0.25
-20 -10 0 10 20
P
DO
S o
f B
Ground state
Energy / eV
B site
H
1st H atom
0.0
0.1
0.2
0.3 N 2s
N 2p
-20 -10 0 10 20
PD
OS
of
N
Energy / eV
N site
π* σ* π* σ* B site- without H N site- without H
Wu et el J. Chem. Phys.,
121 (17), 8481 (2003).
H atom chemisorbs
on the BN
The HOMO of H interacts
with the LUMO of the BN
20
H
2nd H atom
H attached to B –Neighboring B&N
Neighboring B site
Ground state
Neighboring N site
Neighboring N site
Neighboring B site
-20 -10 0 10 200.0
0.1
0.2
0.3
Energy / eV
N 2s
N 2p
N P
DO
S
0.0
0.1
0.2
0.3
B P
DO
S
B 2s
B 2p
Why H/D prefers to adsorb on B site ??
21
2H attached to adjacent B&N Zohu et al : Most stable
configuration
NEXAFS calculation : PDOS of B1s/N1s to LUMO transition
Clear spectral change in π* observed for B and N sites 22
The hydrogenation properties of a h-BN thin film were investigated
as a model material of BN nanomaterials for chemisorption-based
hydrogen adsorption.
The degree of the deuteration was estimated to be 29 % from the
spectral change of the B 1s XPS spectra.
The XPS and NEXAFS spectra of h-BN on Ni(111) were interpreted
using the DV-Xα method, considering the core-hole effect.
The results for the B and N sites implied that deuteration mainly
occurs on B sites. The PSID results support the idea that B sites of BN
are preferentially adsorbed by atomic deuterium
Finally, I concluded that atomic hydrogen is preferentially adsorbed
on B sites in a single hydrogen adsorption mechanism on BN material.
Summary
23
24
Selective adsorption of atomic hydrogen
on a h-BN thin film
Outline
1. Introduction
2. Sample preparation & Deuteration.
3. TOF
4. NEXAFS- Experiment & Calculation.
5. XPS-Experiment & Calculation.
6. PSID.
7. Why H/D prefers to adsorb on B site ?
Kaveenga Rasika Koswattage
the "forever fuel" that we can never run out of
HYDROGEN
It’s abundant, clean, efficient, and can be derived from diverse domestic resources.
Light-duty vehicles
Light storage system
Storing hydrogen in light storage system is required Materials at nano scale
Carbon nanotubes (CNTs) are allotropes of
carbon(同素异形体）(graphite 石墨，diamond钻石， Fullerene）with a cylindrical
nanostructure. Nanotubes have been
constructed with length-to-diameter ratio of
up to 28,000,000:1,which is significantly
larger than any other material.
Discovered in 1991 by the Japanese electron microscopist Sumio Iijima.
Carbon nanotubes
(a) (b)
Crystal structures: (a). Hexagonal boron nitride (h-BN) (b). Graphite.
Boron nitride (BN) nanomaterials
Transportation Fuel cell power technology Renewable
Sustainable
Light-duty vehicles
Light storage system
CNT
US DOE on board hydrogen system has proposed to achieve 5 wt % hydrogen storage by
Introduction
H2 H2
H2 H2 H2 H H
H H H
Quality of the sample problems
Contamination
Defects
Diameter dependence.
Single wall /Multi wall
1996 1998 2000 2002 2004 2006 2008
0.01
0.1
1
10
SW-CNT- Physisorption BNNT- Physisortption .
SW-CNT- Chemisorption
Hyd
rogen
up
tak
e /
wt%
Year
DOE target
Hydrogenation by ,
chemisorption >
physisorption
Nikitin et al. Nano
Letters, 8, 162 (2008).
Physisorption Chemisorption
Reported hydrogen uptakes …..
BNNT One of the
promising
candidates
Volumetric and gravimetric hydrogen density of some selected hydrides.
Hydrogenation by chemisorption > physisorption
A. Zuttel et al, Phil. Trans. R. Soc. A 368, 3329 (2010)
For graphite
Hydrogenation degree at saturation coverage of atomic hydrogen
adsorption and desorption of hydrogen as a function of temperature were
reported.
Formation of C-H bonds at the surface under atomic hydrogen treatment
employing X-ray photoelectron spectroscopy (XPS) was reported.
A. Nikitin et al, Ruffieux et al C-H
Hydrogenation
degree = 0.370.05
Saturation coverage of atomic hydrogen adsorption values estimated by
XPS and other techniques ( TDS) are coincides .
T. Zecho et al , A. Nikitin et al.
C-H
H adsorbed on neighbor carbon
bending of C–H bonds
2. Hydrogen adsorption on BN is site selective
BN nano-materials
This suggestion/coverage for hydrogen adsorption has not been
experimentally verified
1. Hydrogenation on BNNT > CNT Ex: R. Ma et al ,J. Am. Chem.
Soc. 124 (26) ,7672 (2002).
H
B N
Wu et al., J. Chem. Phys.
121, 8481 (2003).
V.A Margulis et al.,
springer , 275 (2007).
H atom prefers
to adsorb on the
top site of the B
H atom prefers
to adsorb on the
top site of the N
Two hydrogen atoms adsorbed on-top sites
of adjacent B and N atoms Z. Zhou et al., J. Phys. Chem. B
110, 13363 (2002).
Hydrogenation was examined using thin film of h-BN
Ni(111)
substrate
·lattice constant
·atomic distance
lattice
matching
h-BN 2.51 Å
Ni(111) 2.49Å -0.4 %
Pd(111) 2.76Å 10 %
Pt(111) 2.89Å 15.2 %
Borazine
(B3N3H6)
N N B
B B
H
H H
H
H
H N
Ni(111) ~800 ℃
Precursor gas
Well ordered
Highly commensurate
Perfect lattice match
BN film on Ni(111) substrate
Chemical Vapor Deposition
Thin film of h-BN on a Ni(111) substrate was selected for the investigation
h-BN on a Ni(111)
pressure of
1×10-4 Pa
W. Auwarter et al., Surf. Sci.,
429, 229 (1999).
Nagashima et al., Phys.
Rev. B 51, 4606 (1995).
F
BK EhE
X-ray Photoelectron spectroscopy (XPS)
XPS spectra of clean HOPG (a) and H treated
HOPG with H saturated coverage (b).
A. Nikitin et al., Surf. Sci. 602, 2575 (2008).
(a)clean HOPG
(b).H treated
HOPG
180 188 196 204 212 220 228
Vacuum
*
Core level
σ*
Unoccupied
levels
Excitation
Energy
Photon Energy / eV
Ab
sorp
tion I
nte
nsi
ty
Synchrotron
Radiation
*
σ*
Photon Energy (eV)
Ab
sorp
tion
in
ten
sity
(ar
b. un
its.
)
NEXAFS
σ*
*
(a) (b)
Continuum States
Eπ*
Eσ*
IP
IP
FL
ValenceBand σ*
(b). A typical B – Kedge NEXAFS spectrum of
bulk h-BN which shows two features, π* and σ*.
(a). Schematic representation of the processes involved in NEXAFS for unsaturated
compounds with double or triple bonds.
Near-edge X-ray absorption fine structure (NEXAFS)
I. Shimoyama et al., J. Elec. Spec. Relat. Phenom.
137, 573 (2004).
Grazing incidence ： Enhancement of 1s *
Normal incidence ： Enhancement of 1s σ *
E
G razing
incidence
N ormal
incidence
N
G
* s *
O
O s
E
π orbital
σ orbital
E
sp2
θ=20º
θ=90º
Polarization dependence -NEXAFS
C K-edge NEXAFS spectra of single-crystal
graphite at various incident angles (θ )
R.A. Rosenberg et al., Phys.
Rev. B 33, 4034 (1986).
X-ray gun
QMS
Analyzer
Ion gun
Hot filament
system
Ultra high vacuum chamber
Base pressure of the UHV chamber was ~8×10-8 Pa
Experimental
All the experiments were performed at the BL-11A beam line of the Photon Factory.
QMS
Ion gun
Hot filament system
XPS-
analyzer
Manipulator
SR
I0 Monitor
(Au mesh)
Experimental chamber set up for the experiment at the BL-11A
Bending magnet beamline
Energy range of 70 eV – 1900 eV
Max. photon flux of 1012 photons/sec
Resolving power 500 - 4000
Experimental
BL- 11A at KEK-PF
Ni(111)
STEP 1. Ar+ sputtering-
{Ni(111) substrate}
STEP 2. Heated Ni(111) substrate to ~800 ℃
STEP 3.
Introducing borazine
Borazine (B3N3H6)
N N B
B B
H
H H
H
H
H N
Sample preparation
Chemical Vapor Deposition
pressure of
1×10-4 Pa
Nagashima et al., Phys. Rev. B 51, 4606 (1995).
Hot filament system
BN/Ni(111)
07.0 A
10.0 V
2 3 4 5 6 7 8
800
1000
1200
1400
1600
1800
2000
T
emper
ature
/ C
Current / A
Degree of dissociation of a hot filament
system as a function of temperature Filament temperature as a function of current
C. Eibl et al, J. Vac. Sci. Technol. A 16, 2979 (1998).
2. NEXAFS
Au mesh
I(h)
1. XPS
I0 (h)
Synchrotron
radiation ring
A
A
hν=700 eV
I(h)
I0 (h)
Spectroscopic measurements…………..
Schematic diagram of the
experimental arrangement
for ion TOF measurements
CFD
MCA
Pre-AMP
TAC 1/312
Divider
RF cavity
( 500 MHz) AMP
STOP
START
3. TOF
Experimental
Thin film of BN on Ni(111)
Ni (111)
BN thin film
IN1s IB1s
INi3s
t
Composition ratio & Thickness
0
500
hv = 192.1 ,
H+
D +
0
D +
H+
Sample annealed
at 200 C Supposed to
be due to
water
hν =
192.1 eV
sN
sB
sB
sN
I
I
hν
hν
N
B
1
1
1s1B
1s1N
)(
)(
][
][
s
s
)/exp(
)/exp(1
)(
)(
BNin 3s Ni
BNin 1s B
Ni
B
Niin 3s Ni
BNin 1s B
3s Ni
1s B
3s Ni
1s B
s
s
t
t
n
n
hν
hν
I
I
XPS spectrum of as-deposited
BN film on Ni(111)
Equations for estimation of Composition ratio & Thickness
Thickness of the BN film was estimated to be 6.6 Å
[B]/[N] was estimated to be 0.98
C 1s
Sample annealed at 200 C
TOF spectrum after deuterium treatment
Supposed to be
due to water
hν = 192.1 eV
After deuterium treatment
K.R. Koswattage et al., J. Chem. Phys., 135, 014706 (2011).
NEXAFS -Spectral change by atomic deuterium treatment
400 410 420 430 440In
ten
sity
(arb
. u
nit
)
N K-edge
Photon Energy / eV
Before
After
188 192 196 200 204
Inte
nsi
ty (
arb
. u
nit
)
B K-edge
Photon Energy / eV
π*B
π*A σ* Before
After
Experimental results-NEXAFS
Interaction change between
film and substrate by
deuterium adsorption
1.Formation of B-D bond or
2. Interaction change between film and
substrate by deuterium adsorption or
3.Resultant of these two phenomena.
K.R. Koswattage et al., J. Chem. Phys., 135, 014706 (2011).
Spectral change between π*A
and σ*showing similar
polarization dependence like
π*A & π*B .
185 190 195 200 205 210
Inte
nsit
y (
arb
. u
ni )
Photon Energy / eV
angle ( ) = 20
angle ( ) = 35
angle ( ) = 55
B
D
out of plane orientation – B-D bonds are perpendicular to the surface
out of plane orientation was used for DV-Xαcalculation
Spectral change between π*A & σ*
Formation of B-D bond
E SR
Polarization dependence NEXAFS
BN film- B27N27H18
Unoccupied
states
Vacuum
π*
σ* 0.5
0.5
One H on B site
One H on N site
Two H on adjacent B&N site
DV-Xα Calculation
Slater’s transition theory
☆Minimal basis set :
•2s & 2p for B&N
•1s for H
▲Model clusters :
optimization :
Win MOPAC / AM1
Model clusters Calculation method
( A molecular orbital calculation method)
B
N
H
1. One H attached to B site
DV-Xα Calculation- NEXAFS
B 1s to LUMO
π* σ*
B-Without H
B-With H
N-With H
N-Without H
2. One H attached to N site N 1s to LUMO
π* σ*
DV-Xα Calculation- NEXAFS
3. One H attached to B site-Neighbouring B and N
Neighbouring B
Neighbouring N
DV-Xα Calculation- NEXAFS
4. One H attached to N site-Neighbouring B and N
Excitation Energy / eV
Excitation Energy / eV
188 192 196 200 204 208
400 404 408 412
Inte
nsi
ty (
arb
. u
nits
) B 2p
B 2s
N 2p
N 2s
Neighbouring B
Neighbouring N
DV-Xα Calculation- NEXAFS
Cluster dependence B
N
H
B48N48H24
B12N12H12
DV-Xα Calculation- NEXAFS
B48N48H24 B12N12H12
XPS-Spectral change by atomic deuterium treatment
188 190 192 1940
1
2
3
4
Inte
nsi
ty (
arb
. u
nit
)
Binding Energy / eV
Additional component appeared at low BE
Before
After
B 1s
396 398 400 4020
1
2
3
Inte
nsi
ty (
arb
. u
nit
)
Binding Energy / eV
Broadening to high BE
Before
After
N 1s
Experimental results-XPS
Cluster
Chemical shift ( eV)
Hydrogenated sites Neighboring sites
B 1s N 1s B 1s N 1s
B27N27H18+HB -0.7 N/A N/A -0.4
B27N27H18+HN N/A +2.2 -2.0 N/A
B27N27H18+2HBN -1.6 +2.2 N/A N/A
DV-Xα Calculation- XPS
188 190 192 1940
1
2
3
4
Inte
nsi
ty (
arb
. u
nit
)
Binding Energy / eV
Before
After
B 1s
396 398 400 4020
1
2
3
Inte
nsi
ty (
arb
. u
nit
)
Binding Energy / eV
Before
After
N 1s
XPS calculation
XPS-Spectral change by atomic deuterium treatment
B-D
NEXAFS and XPS results imply that atomic deuterium
adsorption occurred on B site more preferentially than on N site
187 188 189 190 191 192 193 194 195
Binding Energy / eV
Inte
ns
ity
( a
rb .
un
i )
BD
A
A* Rtop
Degree of deuteration was estimated to be 29 % considering only B site.
,100 topD
D
RAB
B
Degree of deuteration (%) =
Degree of deuteration
Deuterium ion
X-ray
（N excitation）
X-ray
（B excitation）
Why PSID ?
NEXAFS and XPS spectroscopic methods are not considered to
be methods of directly detecting hydrogen from the surface
Photon stimulated ion desorption ( PSID)
PSID can be employed to study hydrogen adsorption sites on a BN film
Time of flight mass spectrometer
Single bunch
SR
PF- Storage
ring
CFD
MCA
Pre-AMP
TAC 1/312
Divider
RF cavity
( 500 MHz)
AMP
STOP
START
TOF-MS measurement system
Schematic diagram of the experimental arrangement for ion TOF measurements
PSID yield () spectra for D+ ion
Clear increase at the B
K-edge
0
40
80
120
160
184 188 192 196
395 400 405 410
B
Photon Energy / eV
N
D+
des
orp
tio
n y
ield
(
arb
. u
nit
)
Electron excited to
* state
B-D anti bonding
state
does not show clear increase in the N K-edge
N sites adsorbed by deuterium was smaller than B
K.R. Koswattage et al., J. Appl. Surf. Sci., 258, 1561 (2011).
Why H/D prefers to adsorb on B site ??
Explanation is based on the frontier orbital theory
0.00
0.05
0.10
0.15
0.20
0.25
-20 -10 0 10 20
P
DO
S o
f B
Ground state
Energy / eV
B site
H
1st H atom
0.0
0.1
0.2
0.3 N 2s
N 2p
-20 -10 0 10 20
PD
OS
of
N
Energy / eV
N site
π* σ* π* σ* B site- without H N site- without H
Wu et el J. Chem. Phys.,
121 (17), 8481 (2003).
H atom chemisorbs
on the BN
The HOMO of H interacts
with the LUMO of the BN
H
2nd H atom
H attached to B –Neighboring B&N
Neighboring B site
Ground state
Neighboring N site
Neighboring N site
Neighboring B site
-20 -10 0 10 200.0
0.1
0.2
0.3
Energy / eV
N 2s
N 2p
N P
DO
S
0.0
0.1
0.2
0.3
B P
DO
S
B 2s
B 2p
Why H/D prefers to adsorb on B site ??
2H attached to adjacent B&N Zohu et al : Most stable
configuration
NEXAFS calculation : PDOS of B1s/N1s to LUMO transition
Clear spectral change in π* observed for B and N sites
The hydrogenation properties of a h-BN thin film were investigated
as a model material of BN nanomaterials for chemisorption-based
hydrogen adsorption.
The degree of the deuteration was estimated to be 29 % from the
spectral change of the B 1s XPS spectra.
The XPS and NEXAFS spectra of h-BN on Ni(111) were interpreted
using the DV-Xα method, considering the core-hole effect.
The results for the B and N sites implied that deuteration mainly
occurs on B sites. The PSID results support the idea that B sites of BN
are preferentially adsorbed by atomic deuterium
Finally, I concluded that atomic hydrogen is preferentially adsorbed
on B sites in a single hydrogen adsorption mechanism on BN material.
Summary
6th International conference of DV-Xα was held in Korea .
Awarded best research in poster and oral section.
