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V (V vs Ag/AgCl)
-0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0
I (m
A/c
m2)
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
Dark measurement
UV ON
Time (sec)
0 1000 2000 3000 4000 5000
I (m
A/c
m2)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
V (V vs Ag/AgCl)
-0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0
I (m
A/c
m2)
-0.04
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
Dark measurement
UV ON
Time (sec)
0 1000 2000 3000 4000 5000
I (m
A/c
m2)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
V (V vs Ag/AgCl)
-0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0
I (m
A/c
m2)
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Dark measurement
UV ON
AbstractInGaN/GaN core-shell structure have gained increasing interest as photo anodes for water-splitting due to their adjustable band gap, whichcan be tuned to absorb a wide range of the solar spectrum. Although promising, their stability in liquid environments has been hindering theiruse in photoelectrochemical (PEC) water-splitting. In an attempt to understand and evaluate these instabilities, we tested GaN nanorods indifferent electrolytes. Cyclic voltammetry and time dependant photocurrent data are presented, together with SEM images and EDX, beforeand after etching, to show the effect of the tests on the specimens. Despite these instabilities, our initial results, obtained on InGaN/GaNcore-shell nanorods structures showed promising results.
Evaluating the performance of GaN and InGaN/GaN core-shell nanorods structures as photo anodes in photoelectrochemical
water splittingV. Adamaki1, E. D. Le Boulbar2, A. Sergejevs2, C. Clarke2, C. R. Bowen1
1Mechanical Engineering Department, University of Bath, BA2 7AY, UK2Electrical Engineering Department, University of Bath, BA2 7AY, UK
InGaN/GaN core-shell nanorods
Photoelectrochemical (PEC) measurements
The research leading to the materials development and characterisation was from the European Union’s Seventh Framework Programme (FP7/2007-2013)/ERC Grant Agreement no. 320963 on Novel Energy Materials, Engineering, Science and Integrated Systems (NEMESIS).
Energy Harvesting 2016
• 3-electrode electrochemical system• Ag/AgCl reference electrode and a
platinum wire as a counter electrode in 0.1M Na2SO4 electrolyte
• 6 wavelengths UV to visible light• Homogeneous illumination
GaN nanorods
4326 SQW_blue (455nm)
V vs Ag/AgCl (V)
-0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0
I (m
A/c
m2)
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
0.12
OFF
ON_blue
InGaN/GaN under blue light (451.22nm)
Wavelength (nm)
IPCE (%)0 V vs SHE
IPCE (%) 0.74 V vs SHE
451.22 1.23 13.4
527.18 1.34 10.7
593.57 0 0.84
629.62 0 0.18
!
After a few runs…
4335 6MQWs_blue (455nm)
V vs Ag/AgCl (V)
-0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0
I (m
A/c
m2)
-0.01
0.00
0.01
0.02
0.03
0.04
OFF
ON_blue
Reduced photocurrent under blue light (451.22nm)
583 nm2 μm
412 nm
Nanorodssites
• Electrochemically stable at 0 V vs SHE.• Nanorods etched when potential is applied• Test different electrolyte
At
0 V
vs
SHE
At
0.6
V v
s SH
EA
t 1
V v
s SH
E
Time (sec)
0 1000 2000 3000 4000 5000
I (m
A/c
m2)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
V (V vs Ag/Ag/Cl)
-0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0
I (m
A/c
m2)
0.0
0.5
1.0
1.5
2.0
2.5
Dark measurement
UV ON
OFF
OFF
OFFOFF
ON
ON
ON
GaN nanorods
Line spectrum along the length of the InGaN/GaN core-shell
structure
0.0 0.5 1.0 1.5 2.0 2.5 3.0
distance (µm)
2.0
2.5
3.0
3.5
en
erg
y (
eV
)
1
10
100
1000
CL
inte
ns
ity (c
ou
nts
)
GaN/InGaN regrowth
Passivation layer
Metal maskPlasma etching
Nanorod array
Fabrication process
GaN under UV light (368 nm)
ON
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