cu(i) based p-type metal oxide: a remarkably...
TRANSCRIPT
AbstractIn order to address the challenges in sustainable global development, considerable efforts
have been made to replace the conventional fossil fuels with the renewable resources of
energy, using photocatalysts and photo-electrochemical cells (PECs) by harvesting solar
energy. Here, we propose an efficient and commercially feasible solar water splitting using
Cuprous oxide (Cu2O) as photo-absorbing electrode material. Cu2O is an intrinsically p-
type semiconductor, with a direct band gap of 2.1 eV, making it one of the potential
semiconductors to be used for the photo-electrolysis of water for hydrogen generation.
However, it has a poor solar-to-hydrogen (STH) conversion efficiency because of the fast
recombination of electrons and holes, and weak stability in the aqueous medium. Here, we
describe an extensive study on the efficiency enhancement, while addressing the stability
of Cu2O against the photo-corrosion.
IntroductionHYDROGEN• Most abundant • High energy yield per mass• Environment friendly
U.S. Drive in partnership with U.S. DOE
Cu(I) METAL OXIDE:• Band gap : 2.0 - 2.1 eV• Proper Valence and Conduction band
edges at 1.43 V and -0.75 V • Abundant, non-toxic and low-cost• Theoretical photo-current density, Jp
= – 14.7 mA/cm2
• Theoretical ηSTH = 18%
Materials and MethodsChemicals required:Copper lactate solution, FTO substrates,ethanol, acetone, distilled water,KCl, NaOH, Na2SO4, HCl, H2SO4.
Instruments/ Set-up:Potentiostat - autolab, Xenonlight source (𝜆: 400 - 1100 nm),PEC cell, pH meter, thermometer.Electrodes:Pt wire, Ag/AgCl.
Methods:• Electrodeposition method for planar film deposition and fabrication• Hydrothermal method for Cu2O nanowires synthesis• Drop- casting method for film deposition of Cu2O nanowires• Effective pre-treatment of FTO substrates for enhancing stability
References1. Bak, T., Nowotny, J., Rekas, M., Sorrell, C.C., 2002. Photo-electrochemical hydrogen
generation from water using solar energy. Int. J. Hydrogen Energy 27, 991–1022.2. Dodds, P.E., Mcdowall, W., 2012. A review of hydrogen production technologies for energy
system models. UCL Energy Institute, Univ. Coll. London 1–22.3. Azevedo, J., Tilley, S.D., Schreier, M., Stefik, M., Sousa, C., Araujo, J.P., Mendes, A.,
Grätzel, M., Mayer, M.T., 2016. Tin oxide as stable protective layer for compositecuprous oxide water-splitting photocathodes. Nano energy, 10–16.
AcknowledgementAuthors would like to thank IITD for providing necessary lab facilities to carry out the experiments and characterizations.
Conclusions1. Planar Cu2O and nanowires of a resaonable aspect ratio were successfully synthesized2. Both the thin films were deposited on FTO substrates with an overall average
thicknesses of 4 µm3. A remarkably enhanced photocurrent density was achieved in the nanowires samples
from -0.15 mA/cm2 to – 3.19 mA/cm2 resulting into a more efficient solar water splitting
4. The stability of Cu2O thin film against photo-corrosion could be successfully prevented by the rigorous pre-treatment of FTO substrates using the oven-dry and nitrogen-dry methods
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Industrial SignificanceThe method of producing hydrogen as an alternative fuel by means of photo-
electrochemical water splitting is a completely environment friendly and cost-effective
procedure. The monolithic design of PEC using the low-cost semiconductor photocathode
material (Cu2O) and all operations at room temperature make it feasible to produce
hydrogen commercially.
Technology Readiness LevelThe set-up and all investigations so far have been done at the lab scale. After investigation
of hydrogen generation rate, the technology shall be upgraded to the pilot scale.
Cu(I) based p-type metal oxide: A remarkably efficient photo-
electrocatalyst for solar water splitting for hydrogen generation
Iqra Reyaz Hamdani, and Ashok N. Bhaskarwar*
Results
Industry Day Theme # 4: Sustainable Habitat
Fig.1 Principle of photo-assisted electrolysis
of water using photo-anode.
• Based on solar energy
• Environmentally safe
• Suitable for both small and
large scale
Fig.2 Photo-water splitting by Cu2O photocathode.
Fig.3 Electrodeposition of Cu2O from copper lactate solution.
U.S. Drive in partnership with U.S. DOE, 2016
Cu2O nanowires
drop
-0.60
-0.40
-0.20
0.00
0.20
0.40
-1.5 -1 -0.5 0
Ph
oto
cu
rre
nt
de
nsi
ty (m
A/c
m2 )
Voltage, V vs Ag/AgCl
-2.5
-2
-1.5
-1
-0.5
0
0 500 1000 1500 2000
Cu
rren
t (m
A)
Time of deposition (s)
-0.004
-0.002
0
0.002
0.004
-2 -1 0 1 2Cu
rre
nt
de
nsi
ty,
A/c
m2
Voltage, V vs Ag/AgCl
-0.006
-0.004
-0.002
0
0.002
0.004
0.006
0.008
-1.5 -1 -0.5 0 0.5 1 1.5
Cu
rre
nt
de
nsi
ty, A
/cm
2
Voltage, V vs Ag/AgCl
a) b) c)
d)
Fig. 4 a) TEM micrograph of Cu2O nanowires b) SEM micrograph of Cu2O nanowires c) Film
deposition on FTO by drop casting method d) Fabrication of Cu2O nanowires as photo-electrode.
V = -0.35V
Fig. 5 SEM micrograph of planar Cu2O. Fig. 6 a) i vs t response for electrodeposition of planar Cu2O
b) bare FTO substrate c) Cu2O film electrodeposited on FTO.
a) b) c)
Fig. 7 a) Film thickness of Cu2O nanowires: 4 µm b) film thickness of electrodeposited Cu2O: 3.9 µm,
using optical profilometer.
-40
-20
0
20
40
-1.5 -1 -0.5 0
Ph
oto
cu
rre
nt
de
nsi
ty (
10
-4A
/ cm
2)
Voltage, V vs Ag/AgCla)b)
Fig. 8 a) Photocurrent density of planar Cu2O: -0.15 mA/cm2 b) Photocurrent density of Cu2O
nanowires: -3.19 mA/cm2 at -1V vs Ag/AgCl.
a) b) c)
Fig. 9 a) Initial pre-treatment of FTO b) CV depicting instability of Cu2O film in aqueous medium
after 5th cycle c) Photographic image of unstable Cu2O photocathode.
a) b)
Fig. 10 a) Final pre-treatment
of FTO b) CV depicting good
stability of Cu2O thin film even
after 10th cycle.
a) b)