Transcript ELECTROCHEMICAL SINTESYS OF Cu2O FROM DIFFERENT …

ELECTROCHEMICAL
SINTHESYS OF Cu2O FROM
DIFFERENT APPLICATION
ASPECTS
Mirjana Rajčić-Vujasinović, Zoran Stević,
Zvonimir Stanković, Vesna Fajnišević,
Sanja Bugarinović
Tehnički fakultet u Boru, Bor, VJ 12 19210 Bor
Copper (I) oxide
Other names: Cuprous oxide, Cuprite (mineral), Red copper oxide
Fig. 1: Cuprous oxide powder
Fig. 2: Cybic cristal structure
of cuprous oxide
Properties
Molecular formula
Molar mass
Appearance
Density
Melting point
Solubility in water
Crystal structure
Cu2O
143.09 g/mol
brownish-red solid
6.0 g/cm³, solid
1235 °C (1508 K)
insoluble
cubic
Application

Cuprous oxide is commonly used as a pigment, a fungicide and an
antifouling agent for marine paints.

Copper (I) oxide was the first substance known to behave as a
semiconductor.

Nanomaterials exhibit novel physical properties and play an important role
in fundamental research.

In diverse fields such as solar cells and photovoltaic materials and electro
chromic coatings.

Lithium batteries.
Experimental

Two processes were described and tested:
1. Anodic electrosynthesis:
Cu Cu(I) + e¯
2Cu(I) + OH¯ Cu2O + H(I)
2. Potentiostatic deposition of cuprous oxide by cathodic reduction of
alkaline cupric lactate solution.

Electrodeposition is a versatile and low-cost technique for preparing thin
films of oxide.

The point of the work is synthesis of cuprous oxide which can be use as
anodic material in the form of thin film in lithium batteries and solar cells.
Anodic electrosynthesis

Cuprous oxide was obtained by electrolysis of pure copper in NaCl
solution with copper electrodes.

Parameters: current density, concentration of NaCl solution,
temperature, circulation rate and time of 1 hour.

The quality of obtained copper (I) oxide was tested by X-ray diffraction
analysis.
XRD analysis show appereance of CuCl and a few CuO and elementary
copper.
The quality of the obtained copper is above 99 % and the rest are
admixtures.
7
A
8
5
V
4
9
3
1
2
10
6
11
12
Fig. 1. Sketch of the laboratory device for
electrochemical synthesis of Cu2O
1 – electrochemical cell;
2 – vessel for the cell heating;
3 – electrodes;
4 – thermometer;
5 – reservoir for electrolyte;
6 – thermostate;
7 – ampermeter;
8 – voltmeter;
9 – overflow;
10 – overflow vessel;
11 – Cu2O flowlet;
12 – vessel for Cu2O
NORDOX
200 (A/m2)
400 (A/m2)
600 (A/m2)
800 (A/m2)
70
60
50
TRANSPARENCY (%)
TRANSPARENCY (%)
60
40
30
20
10
0
0
NORDOX
200 (A/m2)
400 (A/m2)
600 (A/m2)
800 (A/m2)
70
50
40
30
20
10
3
6
9
12
15 18
TIME (min)
21
24
Fig. 3: C = 1 M; t = 80 °C
27
30
0
0
3
6
9
12
15 18
TIME (min)
21
24
Fig. 4: C = 2 M; t = 80 °C
27
30
NORDOX
200 (A/m2)
400 (A/m2)
600 (A/m2)
800 (A/m2)
1000 (A/m2)
70
50
60
TRANSPARENCY (%)
TRANSPARENCY (%)
60
40
30
20
10
0
0
NORDOX
200 (A/m2)
400 (A/m2)
600 (A/m2)
800 (A/m2)
1000 (A/m2)
70
50
40
30
20
10
3
6
9
12
15 18
TIME (min)
21
24
Fig. 5: C = 3 M; t = 80 °C
27
30
0
0
3
6
9
12
15 18
TIME (min)
21
24
Fig. 6: C = 4 M; t = 80 °C
27
30
Jk = 400 A/m2
T = 60 0C
CNaCl = 3 M
Fig. 7: XRD pattern for Cu2O electrochemically synthesized under the bath
temperature of 60 °C
Potentiostatic deposition of cuprous oxide

Cuprous oxide has not been commonly used because its low energy
conversion efficiency (≤1%), which results from the fact that the lightgenerated charge carriers in micron-sized Cu2O grains are not efficiently
transferred to the surface and lost due to recombination.

For randomly generated charge carries, the average diffusion time from
the bulk to the surface is given by τ = r²/π²D, where r is the grain radius
and D is the diffusion coefficient of the carrier.

If the grains radius is reduced from micron- to nano-size, the opportunities
for recombination can be dramatically reduced.

Therefore, the preparation of nanocristallyne Cu2O thin films is a key to
improve the performance of solar devices.
Experimental

The potentiostatic deposition of cuprous oxide has been conducted on
stainless steel electrodes, platinum and copper electrodes by the cathodic
reduction of an alkaline cupric lactate solution.

The applied potentials were -0,4 V, -0,5 V, -0,6 V and – 0,8 V vs SCE.

The pH of the bath was adjusted between 7-10 by the addition of sodium
hydroxide.

The bath temperature was room temperature.

The conventional three-electrode cell was used for electrochemical
characterization of sample with saturated calomel electrode (SCE) as a
reference electrode.

Electrodeposition was carried out under potentiostatic mode using the
system for electrochemical measurement consisted of hardware (PC, ADDA converter NI–621 produced by National Instruments and analog
interface developed on Technical faculty in Bor) and software for
excitation and measurement (LabVIEW platform and application
software).

The possible reactions during the cathodic reduction of cupric lactate
solution are:
2Cu2+ + 2e- + H2O = Cu2O + 2H+
(1)
Cu2+ + 2e2- = Cu
Cu2O + 2e1- + 2H+ = 2Cu + H2O
(2)
(3)
2
0
200
400
600
800
1000
-2
I, [mA]
I, [mA]
0
-4
-6
-8
0,1
0
-0,1 0
-0,2
-0,3
-0,4
-0,5
-0,6
-0,7
-0,8
200
400
t, [s]
600
t, [s]
potential -0,6 V
potential -0,6 V
b)
I, [mA]
a)
10
5
0
-5 0
-10
-15
-20
-25
-30
-35
-40
100
200
300
400
500
600
t, [s]
potential -0,6 V
c)
Fig 8: Electrochemical reduction current as a function of time
a) steel electrode: b) platinum electrode
c) copper electrode
800
Electrochemical characterization
15
10
10
5
5
0
-0.7
-0.5
-0.3
-0.1
0.1
-5
I, [mA]
-0.9
I, [mA]
0
-10
-1
-0.8
-0.6
-0.4
-0.2
-5 0
-10
-15
-20
-15
-25
-20
-30
-25
E [V] vs SCE
E [V] vs SCE
50 mV/s
10 mV/s
a)
b)
Fig. 9: Cyclic voltammograms of Cu2O deposition from copper (II) lactate solution at
pH=9 on the steel electrode:
a) the applied potential of -0.6 V (vs. SCE) b) the applied potential of -0.8 V (vs. SCE)
a)
b)
c)
Fig. 11:Microscopic pictures of electrodeposite of cuprous oxide on steel electrode
a) applied potential -0.5 V (underlying mark between electrode and film)
b) applied potential -0.6 V (after 2 minutes of electrodeposition)
c) applied potential -0,5 V (middle of electrode)

In Fig. 12 it can be seen that with
cuprous oxide (dark area in the
middle), on the electrode surface
elementary copper appears, too .

This can be explained by the
reduction of cuprous oxide (reaction
3).
Cu2O + 2e1- + 2H+ = 2Cu + H2O (3)
Fig. 12: Cuprous oxide and
elementary copper on the steel
electrode after electrodeposition at the
-0.8V
Fig. 13. SEM photographs of Cu2O films deposited at various
bath temperatures: (A)0, (B)30, (C) 45, and (D) 60 °C.
[ Y. Tang, Materials Letters 59 (2005) 434-438)]

Scanning electron micrographs
(SEM) obtained on Cu2O thin
film surfaces deposited at
different bath temperatures for 2
h are shown in Fig. 13.

In the case of 0 (Fig. 13A) and
30°C (Fig. 13B), spherically
shape grains with a 40~50 nm
diameter are observed.

Similar grain structures have not
been previously reported for the
electrodeposited Cu2O thin film.

However, for bath temperatures
above 38°C, Cu2O grain size
rapidly goes up.

Electrodepositing
at
45°C
considerably changes the surface
morphology,
promotes
the
formation of highly branched
dendrite, and enlarges the grain
size from 40 ~ 50 to 200 ~ 500
nm as demonstrated in Fig. 13
(C).

Therefore, the bath temperature
must be controlled in the range
of
0~30°C
to
obtain
nanocrystalline Cu2O thin film.
Conclusion

Anodic synthesis of Cu2O can give a variety of different colors of the
product depending on its grain size. The grain size, itself, depends on the
current density, concentration of NaCl, pH, temperature and some other
less important parameters.

The applied potential has strong effect on the composition and
microstructure of Cu2O films obtained by cathodic reduction.

Pure Cu2O films can be made with applied potential between - 0,2 and
-0,4 to -0,5 V (vs. SCE) (Fig. 9).

The potentiostatic deposition of cuprous oxide by the cathodic reduction
of an alkaline cupric lactate solution was a method to obtain
nanocristallyne grains of cuprous oxide which can be used to improve the
performance of solar devices.
Literature
[1] Yiwen Tang, Zhigang Chen, Zhijie Jia, Lisha Zhang, Jialin Li,
Electrodeposition and characterization of nanocrystalline films
cuprous oxide thin films on TiO2, Materials Letters 59 (2005) 434–
438.
[2] Y.H. Lee, I.C. Leu, S.T. Chang, C.L. Liao, K.Z. Fung, The electrochemical
capacities and cycle retention of electrochemically deposited Cu2O thin
film toward lithium, Electrochimica Acta 50 (2004) 553–559.
[3] Anne-Lise Daltin, Ahmed Addad, Jean-Paul Chopart, Potentiostatic
deposition and characterization of cuprous oxide films and nanowires,
Journal of Crystal Growth 282 (2005) 414-420.
[4] Shaun N. Atchison, Robert P. Burford, Catherine P. Whitby, D. Brynn
Hibbert, Electrodeposition of copper in quasi-two dimensions from
solution containing sodium sulfate, Journal of Electroanalytical Chemistry
399 (1995) 7 l-77.
[5] Xiang-Min Miao, RuoYuan ,Ya-Qin Chai, Yin-Tao Shi, Yan-Yu Yuan,
Direct electrocatalytic reduction of hydrogen peroxide based on Nafion
and copper oxide nanoparticles modifed Pt electrode, Journal of
Electroanalytical Chemistry 612 (2008) 157-163.
[6] Yanchun Zhou, Jay A. Switzer, Electrochemical deposition and
microstructure of copper (I) oxide films, Scripta Materialia, Vol. 38,
No.11, (1998), 1731-1738.
[7] Shigeyoshi Nakayama, Tokiko Kaji, Takenori Notoya, Toshiyuki
Osakai, Mechanistic study of the reduction of copper oxides in
alkaline solutions by electrochemical impedance spectroscopy,
Electrochimica Acta 53 (2008) 3493–3499.