Graphitic carbon nitrides for energy applications
Noramalina Mansor1, Ana Belen Jorge1, Dan Brett1, Christopher W. Gibbs1, Furio Corà2, Paul F. McMillan2
1Electrochemical
Innovation Lab, Department of Chem. Engineering, University College London, Torrington Place, WC1E 7JE, London, UK; 2Department of
Chemistry, University College London, 20 Gordon Street, WC1H 0AJ, London, UK
Synthesis of Graphitic Carbon Nitrides
(a)
1µm
2
(b)
(c)
75 W
0
0
150
300
450
(c) 1µm
Irradiation
time [min] (d)
1µm
High vacuum
9090
150
300
400
500
400
500time600
600
Irradiation
[min
wavelength
Wavelength
[
3030
0 0
50 100 150 200 250
Irradiation time [min]
-0.6
8
-1.2
0
0 0.0
Discharge,
Intercalation
Catalyst support in PEMFC
(d)
600 ºC
625 ºC
650 ºC
400
500
600
700
nm
800
Fig 4. (a): UV-vis absorption spectra of gCNMs. (b): Image of the change of colour of the gCNMs as the reaction
temperature is increased. (c) H2 evolution of gCNMs under visible light using Pt as co-catalyst. (d): Image of the reactor for
H2 evolution reactions showing the Pt side of the gCNM pellet in H2O/methanol solution.
A. B. Jorge, D. J. Martin, M. T. S. Dhanoa, A. S. Rahman, N. Makwana, J. Tang, A. Sella, F. Corà, S. Firth, J. A. Darr and P. F. McMillan,
J. Phys. Chem. C., 117, 7178 (2013).
Electrodes in Lithium-ion batteries
Current [mA/g]
Commercial Cgraphite anodes
present bottlenecks
associated with
surface passivation
and slow intercalation
kinetics.
1.2 (a)
(b)
(b)
Charge,
Deintercalation
Following accelerated carbon corrosion testing, gCNM exhibits better durability
and gCNM supported catalyst (Pt/PTI/Li+Cl-) exhibits higher stability compared to
commercial carbon black (Vulcan):
175
Vulcan
gCNM
PTI-Li+Cl-
1.00
Normalised change in ECSA
(a)
(c)
150
125
100
(a)
10
100
Discharge,
Intercalation
-1.2
0.0
0.5
1.0
1.5 2.0 2.5
Voltage [V]
3.0
Fig 5. (a): Cyclic voltammetry of gCNM vs Li/Li+ at 10-4 V s-1. (b): ChargeDischarge curves of gCNM-based material at 0.02 A g-1.
A. Belen Jorge, F.Corà, A. Sella, D. Brett, P. F. McMillan, J. Int. Nanotechn., accepted.
• Main intercalation feature at 1 V vs
• Unique structure and chemistry that enable new
intercalation processes not available for pure-C graphite.
Li/Li+.
Pt/Vulcan
Pt/gCNM
Pt/PTI-Li+Cl10
(b)
Number of scans
100
1000
Number of scans
Fig 6. Accelerated carbon corrosion cycling (2000 cycles): (a) the change in double layer capacitance
(calculated at 0.40 V and normalised to 10th scan) of the gCNM materials, and (b) the change in ECSA
(calculated from hydrogen region and normalised to respective initial ECSAs) of gCNM supported catalysts
gCNM supported Pt catalysts
have lower overpotential and
higher methanol oxidation
activity per ECSA compared to
Pt/Vulcan.
gCNM-550
0.25
1
0.75
-0.6
0.50
1000
0.6
0.0
0.75
0.00
Further research is already
being developed to optimize
catalyst particle dispersion and
utilisation
(a)
Fig 7. Methanol oxidation
reaction activity in 1M
CH3OH + 0.1 M HClO4 at
25°C of (a) Pt/Vulcan, (b)
Pt/gCNM, and (c) Pt/PTILi+Cl-
0.60
0.45
0.30
0.15
3.00
j / mA cm-2
ECSA
300
550 ºC
(b)
Catalyst activity depends on particle size, dispersion and interaction with the
catalyst support. Conventional catalyst support (carbon black) is unstable at high
potential leading to corrosion and subsequently a decline in catalytic activity.
Normalised double layer capacitance / %
Absorbance (a.u.)
gCNMs are photocatalytic active for H2 and O2 evolution. Their photoactivity is
strongly influenced by their structure. This can be controlled precisely by modifying
synthesis conditions.
(b)
2.25
1.50
0.75
200
150
(c)
100
50
0.4
0.5
0.6
0.7
0.8
0.9
A (E/V vs RHE)
1.0
1.1
1.2
3
200 2.0
0.5100 1.0 1.5
Irradiation Voltage
time [mi
Applications of Graphitic Carbon Nitrides
Photocatalysis H2 and O2 evolution
625
550
UV+Vi
Charge,
600
Deintercalation
24
0.6
625
Fig 3. (left) Poly(triazine)
650 imide
(PTI) structure.
160.0 (right) SEM
image of PTI.
6060
0
300
300
600
1.2
Current [mA/g]
(+) LiX/KX
(c)
550
650
(d)
(d)32
Visible 300 W
550
600
625
650
0
0
O2 evolution [mol]
(a)
T=
600
(b)
oC
(c)
(c)
120
120
(d)
[μm]
2 evolved
H2 [μmol]
[mol]
evolution
H2H
(2)
4
Vis
UV+ Vis
Fig 2. (left) Liebig’s melon
structure. (right) SEM images
graphitic
2 carbon nitrides.
(b)
1µm
Absorbance [Normalized units]
(+)
4
UV+vis
Absorbance [normalised units]
T= 550-650
550
600
625
650
(a) 6(b)
oC(a)
H2 evolution [mol]
(1)
Fig 1. Structural motifs among gCNMs. (a): Liebig's melon based on heptazine units linked by
-NH- groups. (b): nanocrystalline g-C3N4 based on heptazine units. (c): g-C6N9H3.HCl
prepared by solvothermal synthesis from melamine and cyanuric chloride with Cl- ions (green)
occupying the centres of(a)
C12N12 voids within the layers. (d): g-C3N4 based
6 triazine units.
(b) on
H2 evolution [mol]
• gCNM chemistry extends back to Berzelius, Liebig, Franklin and Pauling who
showed that reactions of N-rich C compounds gave rise to polymeric CxNyHz
materials.
• Structures are formed from s-triazine or heptazine (tri-s-triazine) rings linked by
bridging -NH- or -N= units to form various oligomeric, polymeric and 2D sheet
units related to C-graphite or graphene, but built entirely on heteronuclear C-N
bonds.
• The different chemical valence of N relative to C (one of the three bonds of C in
aromatic sp2 compounds is replaced by a lone pair on N, as represented by the
N replacement in benzene to form aniline) causes voids to appear within the
extended layered structures.
N. Mansor, A. Belen Jorge, F.
Corà, C. Gibbs, R. Jervis, P.
F. McMillan, X. Wang, D. J. L
Brett, ECS Transactions,
2013, 58, 1767-1778.