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1N. Naseri, Department of Physics, SUT
Solar Hydrogen Production
Production Storage Delivery Conversion
http://www.merlin.unsw.edu.au/energyh/hydrogen-faqs/
2N. Naseri, Department of Physics, SUT
Solar Hydrogen Production
3N. Naseri, Department of Physics, SUT
Solar Hydrogen Production
Chou et al. Nano Letters, 2011
Ronge et al. Chem Soc Rev, 2014
Nanostructures for Water splitting
PROS
• Shortened carrier collection pathway
• Improved light distribution
• Quantum size confinement
CONS
• Higher surface recombination
• Lower absorbed photon flux
• Slow inter particle charge transport
Principles of PEC H2 Production
5
Covering 0.1% of total surface (~ 70% of IRAN) by PV system with 10%
efficiency
Rev. Soc. Rev. 2012, 41, 7909
6N. Naseri, Department of Physics, SUT
Solar Hydrogen Production
Brillet et al. Nature Photonics, 2012.
Pinaud et al. Energy Environmental Science, 2013.
Landman et al. Nature Materials, 2017.
Li et al. Catalysts Science & Technology, 2015.
7N. Naseri, Department of Physics, SUT
Solar Hydrogen Production
Suitable band gap (Solar sensitive)
Suitable band vs H2O redox levels (in n-type VB more positive than OX state and
in p-type, CB more negative than RED state)
Stable in wide pH range and against photocorrosion
Low cost
Non-toxicity
Catalytic activity for HER and OER (low over potentials)
Finally, cheaper than PV+ EL & Fossil fuel
Efficient (light harvesting /charge transport)
DOE target for PEC hydrogen production solar-to-hydrogen (STH) efficiency of 10%
with durability of 5000 hours
Hierarchical Morphology
88
Hierarchical Morphology
99
• Tuning morphology: Nanotubes
Enhancing transfer of electron to back contact and hole to
electrolyteUnique electronic properties Increasing surface interface
Hopping between particles
L~10 µm by annealing
Electron Diffusion Coe.200 times more than NPs
Highest surface area
PCCP, 2013, 15, 2632
Hierarchical Morphology
10N Naseri, Department of Physics, SUT
1010
• Nano-branched structures Improving charge separation
Facility of hole consumption
Light trapping in systemh+ Ld ~ nm
Light diff. ~ µm
Increase surface
interface
Branched structure
PEC setup
Photoanode
Pt sheet
Ag/AgCl
Quartz window
Injection to GC
12N. Naseri, Department of Physics, SUT
Solar Hydrogen Production
Naseri et al. Int J Hydrogen Energy, 2012.
Katu et al. Chem Soc Rev, 2014.
Gas chromatography
Take a look at the surface: CV
What is the controlling regime?Is there any other electro-active material on the surface?Is the window potential safe?
LSV to probe photo-responses
Comparing Dark and Light responseHow the photo-response is V-dependent?
Chopping and I-i linearity
Chronoamperometery technique
Stability test
Trap states
)/exp( tD
fi
ft
II
IID
ln
ti tf
Ii
If
On
Off
Transport life time
OC life time
0.01
0.1
1
10
100
-0.9-0.7-0.5-0.3
Potential (V)
Tim
e (
s)
1)( dt
dV
e
kT OCn
Electrochemical Impedance Spectroscopy
Electrochemical Impedance Spectroscopy
Efficiency: 1- IPCE
)/()(
)/(12402
2
mWPnm
mAJIPCE
ph
Efficiency: 2- STH
0
0 100)((%)
I
EEJ apprevP
Efficiency: 3-QE
0
100
200
300
400
500
600
0 50 100 150 200Time (min)
0%-air
0%
1%
2%
5%
10%
20%
inI
HmolAPE
)(2(%) 2
H2
(mm
ol)
For Electro-catalysts: Over Potential (OP)
For Electro-catalysts: Turnover Frequency
Measuring this factor is more beneficial when attemptingcompare intrinsic activity of the electro-catalysts withdifferent specific surface area. TOF (s-1) can be calculatedaccording to following formula:
Here, J(A), NA, F, RF and N are current density obtained fromunite area of the electrode (Am-2), Avogadro number,Faraday constant, roughness factor and the total number ofcobalt atoms expose to the surface in the smooth Co layer(1.25 × 1015), respectively. Furthermore, n is the number ofelectron transferred for evolution of one molecule of O2
which equals to 4
Measuring Real Surface: EC method
Measuring Real Surface: Dye Adsorption
26N Naseri, Department of Physics, SUT
26
ACS Nano, 2014
TNA Decorated with CdS NPs
2727
M. Qorbani et al. Applied Catal B: 2015, 162, 210
28N. Naseri, Department of Physics, SUT
Solar Hydrogen Production
Gholami et al. RSC Advances, 2014.
Qorbani et al. Applied Catal B, 2014.
29
Current Enhancing Approaches
• Surface disorder engineering Making Oxygen vacancies in TiO2
lattice & narrowing band gap
Solar Energy Conversion ~ 24%
Current Enhancing Approaches
• Surface disorder engineeringIn
ten
sit
y (
a.u
.)
467 465 463 461 459 457 455
Ti (2p3/2)
Ti (2p1/2)
0%(air)
0%
1%
Ag mol% 0 (air) 0 1 2 5 10 20
APE (%) 3.6 5.8 9.6 7.4 6.2 6.0 5.0
ND (cm-3) 5.5×1018 6.5×1021 16.3×1021 17.6×1021 17.7×1021 20.7×1021 22.6×1021
Rct (W) 194.5 60.0 40.2 44.5 44.2 44.8 41.6
30
0
20
40
60
80
100
0 20 40 60 80 100 120
Time (s)P
ho
tocu
rren
t d
en
sit
y (
A/m
2)
0% 1% 2% 5% 10% 20%
Electro-catalysts
31
A Major Issue on the Way of Splitting Water: Overpotential
Electro-catalysts
32
Expectations from a proper electrocatalyst:
• Earth abundance,
• Non-toxicity,
• Stability,
• and hopefully, Light absorption.
Morales-Guio et al., Chem. Soc. Rev., 2014, 43, 6555–6569
Electrochemical
X. Deng; ACS Catal. 2014.
Photoelectrochemical
33
34N. Naseri, Department of Physics, SUT
Solar Hydrogen Production
Gimenez & Bisquert, Photo-electrochemical solar fuel production, Springer, 2016
35N. Naseri, Department of Physics, SUT
Solar Hydrogen Production
Gimenez & Bisquert, Photo-electrochemical solar fuel production, Springer, 2016
36N. Naseri, Department of Physics, SUT
Solar Hydrogen Production
Jaramillo, Science, 2007Fabbri, Catal. Sci. Tech. 2014
Seh et al., Science, 2017
Subbaraman, Nature Materials, 2012
Chen et al, Nature Rev., 2007
Chowdhury et al, Nature Comm. , 2018
37N. Naseri, Department of Physics, SUT
Solar Hydrogen Production
Scalability Stability Conductivity controllability
Naseri et al. J Phys. D, 2018, Naseri et al ACS Sustainable Chem. Eng., 2016
CoOx Nanoflakesfor OER
38N. Naseri, Department of Physics, SUT
Solar Hydrogen Production
Naseri et al. RSC Adv. 2017, Naseri et al. J Ind. Chem. Eng. 2017
39N. Naseri, Department of Physics, SUT
Solar Hydrogen Production
Qarechalloo et al, Submitted Saadati et al, to be Submitted
CoOx/TNA Photo anodePEC water splitting
TNA Photo anodePEC Glucose sensing