Photochemical study of micelles in photogalvanic cell for solar energy conver

International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 6, September – October (2013), © IAEME
17
PHOTOCHEMICAL STUDY OF MICELLES IN PHOTOGALVANIC CELL
FOR SOLAR ENERGY CONVERSION AND STORAGE
A.S. Meena*1
, Rishikesh2
, Shribai2
and R.C. Meena2
*1
Department of Chemistry, MLS University, Udaipur, Rajasthan (INDIA) - 313001
2
Department of Chemistry, JNV University, Jodhpur, Rajasthan (INDIA) -342005
ABSTRACT
Photochemical studies of micelles in photogalvanic cell containing Rhodamine 6G-EDTA-
NaLS for solar energy conversion and storage. The observed cell performance in terms of
photopotential, photocurrent, conversion efficiency, fill factor and storage capacity in terms of half
change time are 905.0 mV, 450.0 µA, 1.26 %, 0.2516 and 170.0 minutes on irradiation for 140.0
minutes, respectively. The mechanism is proposed for the generation of photocurrent in
photogalvanic cell.
Keywords: - Photopotential, Photocurrent, Conversion Efficiency, Fill Factor, Storage Capacity.
1. INTRODUCTION
The sun energy is the most readily available non-conventional source of energy which is most
abundantly and freely available renewable source of energy. The new approach for renewable energy
sources has led to an increasing interest in photogalvanic cells because of their reliable solar energy
conversion and storage capacity. The photogalvanic cells are based on some chemical reaction,
which rise to high- energy products on excitation by photons. This cell works on photogalvanic
effect. The photogalvanic effect was first of all recognised by Rideal and Williams [1]
and it was
systematically studied by Rabinowitch [2-3]
, Potter and Thaller [4]
, Eliss and Kaiser [5]
, Rohatgi-
Mukherjee et al. [6]
, Dixit and Mackay [7]
, and Kamet [8]
studies various systems in photogalvanic cell
for solar energy conversion and storage. Studies the performance of dye sensitized solar cells based
on nanocrystals TiO2 films prepared with mixed template method by Gratzel and Regan [9]
. Optimum
efficiency of photogalvanic cell for solar energy conversion has been studied by Albery and Archer
[10]
. Madwani et al., Gangotri and Meena, and Genwa and his coworkers [11-14]
have been used of
some reductant, photosensitizer and surfactant in photogalvanic cells for conversion of solar energy
in to electrical energy. Gangotri and his co-workers [15-17]
have been studied of photogalvanic cell
for solar energy conversion and storage by using some dye with reductant, mixed dye, mixed
reductant and dye with reductant and micelles. Recently, some photogalvanic cells were developed
INTERNATIONAL JOURNAL OF ADVANCED RESEARCH IN
ENGINEERING AND TECHNOLOGY (IJARET)
ISSN 0976 - 6480 (Print)
ISSN 0976 - 6499 (Online)
Volume 4, Issue 6, September – October 2013, pp. 17-26
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on the basis of role of photosensitizer with reductant, photosensitizer with reductant and micelles for
generation of electrical energy by Chandra [18], Chandra and Meena [19-20], Chandra et al. [21],
Joseph et al. [22] and Meena et al. [23]. Present system is the effort to observe the photochemical
study of micelles in photogalvanic cell containing Rhodamine 6G-EDTA-NaLS for solar energy
conversion and storage.
2. EXPERIMENTAL METHODS
Rhodamine 6G (MERCK), NaLS (LOBA), EDTA (MERCK) and NaOH (MERCK) were
used in the present work. All the solutions were prepared in doubly distilled water and the stock
solutions of all chemicals were prepared by direct weighing and were kept in coloured container to
protect them from light. The whole system was set systematically for photogalvanic studies, which
consists of thin foil of electrochemically treated platinum as electrode and saturated calomel
electrodes as a reference electrode. The distance between the illuminated and dark electrode is 45
mm. An ordinary tungsten lamp of 200 W was used as light source. Water filter was used to cut-off
IR radiations. The photopotetial was obtained as the difference between the initial potential of the
system in dark and the equilibrium potential attained by the system under constant illumination. The
potential was first measured in dark and the change in potential on illumination was measured as a
function of time. The solution was bubbled with prepurified nitrogen gas for nearly twenty minutes
to remove dissolved oxygen. Solutions of dye, reductant, micelles and sodium hydroxide were taken
in an H-type glass tube. A platinum electrode (1.0 x 1.0 cm2) was immersed into one arm of H-tube
and a saturated calomel electrode (SCE) was kept in the other. The whole system was first placed in
dark till a stable potential was obtained and then, the arm containing the SCE was kept in the dark
and the platinum electrode was exposed to a 200 W tungsten lamp. A water-filter was used to cut off
infrared radiations. The photochemical bleaching of Rhodamine 6G was studied potentiometrically.
A digital pH meter (Systronics Model-335) and a microammeter (Ruttonsha Simpson) were used to
measure the potential and current generated by the system, respectively. The current–voltage
characteristics of photogalvanic cell have been studied by applying an external load with the help of
a carbon pot (log 470 K) connected in the circuit through a key to have close circuit and open circuit
device. The experimental set-up of photogalvanic cell is given in Figure 6. The effect of variation of
different parameters has also been observed. The rate of change in potential after removing the
source of illumination was 0.93mV min-1
in Rhodamine 6G-EDTA-NaLS.
Figure-1 Experimental set-up of photogalvanic cell

19
3. RESULTS AND DISCUSSION
3.1. EFFECT OF VARIATION OF DYE (RHODAMINE 6G) CONCENTRATION ON THE
CELL
It was observed that the photopotential and photocurrent were increased with the increase in
concentration of the dye. A maximum was obtained for a particular value of Rhodamine 6G
concentrations, above which a decrease in the electrical output of the cell was obtained. The reason
of the change in electrical output is that lower concentration of photosensitizer resulted into a fall in
electrical output because fewer photosensitizer (Rhodamine 6G) molecules are available for the
excitation and consecutive donation of the electrons to the platinum electrode whereas the higher
concentration of photosensitizer (Rhodamine 6G) again resulted into a decrease into electrical output
as the intensity of light reaching the dye molecules near the electrode decrease due to absorption of
the major portion of the light by dye molecules present in the path. The results are given in Table 1.
3.2. EFFECT OF VARIATION OF REDUCTANT (EDTA) CONCENTRATION ON THE
CELL
The photopotential and photocurrent were found to increase with the increase in
concentration of the reductant [EDTA], till it reaches a maximum. On further increase in
concentration of EDTA, a decrease in the electrical output of the cell was observed. The reason of
the change in electrical output is that the lower concentration of reducing agent resulted into a fall in
electrical output because fewer reducing agent molecules are available for electron donation to
photosensitizer (Rhodamine 6G) molecule whereas the higher concentration of reducing agent again
resulted into a decrease in electrical output, because the large number of reducing agent molecules
hinders the dye molecules from reaching the electrode in the desired time limit. The results are given
in Table 1.
3.3. EFFECT OF VARIATION OF MICELLES (NALS) CONCENTRATION ON THE CELL
The effect of variation of (NaLS) was investigated in Rhodamine 6G–EDTA–NaLS system.
It was observed that electrical output of the cell was found to increase on increasing the
concentration of micelles reaching a maximum value. On further increase in their concentrations, a
fall in photopotential, photocurrent and power of the photogalvanic cell was observed. The reason of
the change in electrical output is that the micelles solubilize the dye molecules up to highest extent at
or around their micelles concentration. The results are given in Table 1.
3.4. EFFECT OF VARIATION OF PH ON THE CELL
The effect of variation in pH on photoelectric parameters of cell is studied. It is found that the
cell containing Rhodamine 6G-EDTA-NaLS to be quite sensitive to the pH of the solution. It is
observed that there is an increase in the photoelectric parameters of this cell with the pH value (In the
alkaline range). At pH 12.40 a maxima is obtained. On further increase in pH, there is a decrease in
photoelectric parameters. It is observed that the pH for the optimum condition has a relation with
pKa of the reductant and the desired pH is higher than in pKa value (pH>pKa). The reason of the
change in electrical output is that the availability of the reductant in its anionic form, which is a
better donor form. The above same is reported in Table 1.
3.5. EFFECT OF DIFFUSION LENGTH AND ELECTRODE AREA ON THE CELL
The effect of variation in diffusion length (distance between the two electrodes) on the
photoelectric parameters of the cell (imax, ieq and initial rate of generation of photocurrent) is studied
using H-shaped cells of different dimensions. The effect of electrode area on the photoelectric
parameters of the cell is also reported here. It is observed that both imax and rate of change in initial

20
generation of photocurrent (µA min-1
) increase with respect to the diffusion length whenever the
equilibrium photocurrent (ieq) shows a small decrease with respect to the diffusion length. The reason
of the change in electrical output is that the main electroactive species are the leuco or semi-leuco
form of dye (photosensitizer) and the dye in illuminated and dark chamber respectively. The
reductant and its oxidation product act only as electron carriers in the path. The rate of change in
photoelectric parameters with respect to the diffusion length is graphically presented in Table 2.
Similarly, Table 3 shows rate of change in photoelectric parameter with respect to electrode area. It
is found that the maximum photocurrent show increasing fashion with electrode area whereas the
equilibrium photocurrent (ieq) show decreasing fashion.
Table-1: - Effect of concentration (Rhodamine 6G, EDTA and NaLS) and pH on the cell
[Rhodamine 6G] = 2.59 x 10-5
M; Light Intensity = 10.4 mW cm-2
; [EDTA] = 1.44 x 10
-3
M;
Tempt. = 303 K; [NaLS] = 1.44 x 10-3
M; pH = 12.40
Parameters Photopotential (mV) Photocurrent (µA) Power (µW)
(Rhodamine 6G) × 10-5
M
2.52 787.0 235.0 184.95
2.56 852.0 395.0 336.54
2.59 905.0 450.0 407.25
2.62 828.0 385.0 318.78
2.65 752.0 240.0 180.48
(EDTA) × 10-3
M
1.35 762.0 322.0 245.36
1.40 846.0 392.0 331.63
1.44 905.0 450.0 407.25
1.49 828.0 385.0 318.78
1.54 735.0 302.0 221.97
(NaLS)×10-3
M
1.09 710.0 322.0 228.62
1.12 844.0 398.0 335.91
1.14 905.0 450.0 407.25
1.16 828.0 384.0 317.95
1.19 695.0 288.0 200.16
pH
12.32 762.0 348.0 265.18
12.36 846.0 405.0 342.63
12.40 905.0 450.0 407.25
12.44 828.0 395.0 327.06
12.48 735.0 328.0 241.08

21
Table-2: - Effect of diffusion length
Diffusion Length
DL (mm)
Maximum
photocurrent imax
(µµµµA)
Equilibrium
photocurrent ieq
(µµµµA)
Rate of initial generation of
photocurrent (µµµµA min-1
)
35.0 496.0 464.0 13.78
40.0 502.0 458.0 13.94
45.0 510.0 450.0 14.17
50.0 518.0 444.0 14.39
55.0 526.0 438.0 14.61
[Rhodamine 6G] = 2.59 x 10-5
; [EDTA] = 1.44 x 10
-3
M;
Tempt. = 303 K; [NaLS] = 1.44 x 10-3
M; pH = 12.40
Table-3: - Effect of electrode area
Rhodamine 6G-EDTA-NaLS Electrode area (cm2
)
0.70 0.85 1.00 1.15 1.30
Maximum photocurrentImax (µµµµA) 492.0 500.0 510.0 522.0 532.0
Equilibrium photocurrentieq (µµµµA) 474.0 462.0 450.0 436.0 422.0
[Rhodamine 6G] = 2.59 x 10-5
; [EDTA] = 1.44 x 10
-3
M;
Tempt. = 303 K; [NaLS] = 1.44 x 10-3
M; pH = 12.40
3.6. EFFECT OF TEMPERATURE AND LIGHT INTENSITY ON THE CELL
The effect of temperature on the photoelectric parameters of the cell is studied. The effect of
light intensity on the photoelectric parameters of the cell also investigated here. It is observed that the
photocurrent of the photogalvanic cell is found to be increased with the temperature whereas the
photopotential is decreased. Thereafter, the effect of temperature on total possible power output in
the Rhodamine 6G-EDTA-NaLS cell is also studied and it is observed that there a linear change
between the both. The reason of the change in electrical output is that internal resistant of the cell
decreases at higher temperature resulting into a rise in photocurrent and correspondingly, there will
be a fall in photopotential. The same is presented in Figure 2. Similarly, Figure 3 shows rate of
change in photoelectric parameter with respect to light intensity. The light intensity is measured in
terms of mWcm-2
with the help of solarimeter (CEL Model SM 203). It is found that the
photocurrent show linear increasing fashion with light intensity whereas the photopotential show an
increment in a logarithmic fashion.

22
Figure-2 Variation of photopotential and photocurrent with Temperature
[Rhodamine 6G] = 2.59 x 10-5
; [EDTA] = 1.44 x 10
-3
M;
Tempt. = 303 K; [NaLS] = 1.44 x 10-3
M; pH = 12.40
Figure-3 Variation of photocurrent and log V with light intensity
[Rhodamine 6G] = 2.59 x 10-5
; [EDTA] = 1.44 x 10
-3
M;
Tempt. = 303 K; [NaLS] = 1.44 x 10-3
M; pH = 12.40

23
3.7. CURRENT-VOLTAGE (I-V) CHARACTERISTICS OF THE CELL:
The short circuit current (isc) and open circuit voltage (Voc) of the photogalvanic cells are
measured with the help of a multimeter (keeping the circuit closed) and with a digital pH meter
(keeping the other circuit open), respectively. The current and potential values in between these two
extreme values are recorded with the help of a carbon pot (log 470 K) connected in the circuit of
Multimeter, through which an external load is applied. The current-voltage (i-V) characteristics of
the photogalvanic cells containing Rhodamine 6G-EDTA-NaLS cell is graphically shown in
Figure 4.
Figure-4 Current-Voltage (i-V) Curve of the Cell
[Rhodamine 6G] = 2.59 x 10-5
; [EDTA] = 1.44 x 10
-3
M;
Tempt. = 303 K; [NaLS] = 1.44 x 10-3
M; pH = 12.40
3.8. STORAGE CAPACITY AND CONVERSION EFFICIENCY OF THE CELL:
The storage capacity (performance) of the photogalvanic cell is observed by applying an
external load (necessary to have current at power point) after terminating the illumination as soon as
the potential reaches a constant value. The storage capacity is determined in terms of t1/2, i.e., the
time required in the fall of the output (power) to its half at power point in dark. It is observed that the
cell can be used in dark for 170.0 minutes on irradiation for 140.0 minutes. So the observed storage
capacity of the cell is 121.42 %. The results are graphically presented in Figure 5. The conversion of
the efficiency of the cell is determined as 1.265% with the help of photocurrent and photopotential
values at the power point and the incident power of radiations by using the formula
Vpp x ipp
Fill factor (η) = (1)
Voc x isc
Vpp x ipp
Conversion Efficiency = x100% (2)
10.4 mW

24
Figure-5 Performance of the Cell
[Rhodamine 6G] = 2.59 x 10-5
; [EDTA] = 1.44 x 10
-3
M;
Tempt. = 303 K; [NaLS] = 1.44 x 10-3
M; pH = 12.40
3.9. PERFORMANCE OF THE CELL
The overall performance of the photogalvanic cell is observed and reached to remarkable
level in the performance of photogalvanic cells with respect to electrical output, initial generation of
photocurrent, conversion efficiency and storage capacity of the photogalvanic cell. Table 4 shows the
results are obtained in Azur B-EDTA-CTAB cell.
Table-4:- Performance of the cell
S. No. Parameter Observed value
1. Dark potential 257.0 mV
2. Open circuit voltage (VOC) 1162.0 mV
3. Photopotential (DV) 905.0 mV
4. Equilibrium photocurrent (ieq) 450.0 mA
5. Maximum photocurrent (imax) 510.0 mA
6. Initial generation of photocurrent 25.5 mA min-1
7. Time of illumination 140.0 min
8. Storage capacity (t1/2) 170.0 min
9. % of storage capacity of cell 121.42%
10. Conversion efficiency 1.2653%
11. Fill factor (η) 0.2516
[Rhodamine 6G] = 2.59 x 10-5
; [EDTA] = 1.44 x 10
-3
M;
Tempt. = 303 K; [NaLS] = 1.44 x 10-3
M; pH = 12.40

25
4. MECHANISM
On the basis of these observations, a mechanism is suggested for the generation of
photocurrent in the photogalvanic cell as:
4.1. ILLUMINATED CHAMBER
Dye hν
Dye* (3)
Dye* + R Dye–
(Semi or leuco) + R (4)
AT PLATINUM ELECTRODE:
Dye –
Dye + e –
(5)
4.2. DARK CHAMBER
AT CALOMEL ELECTRODE:
Dye + e
-
Dye–
(Semi or leuco) (6)
Dye –
+ R+
Dye + R (7)
Where Dye, Dye*, Dye–
, R and R+
are the dye, excited form of dye, semi or leuco form of
dye, reductant and oxidized form of the reductant, respectively.
5. CONCLUSION
On the basis of the results, it is concluded that micelles (NaLS) with reductant (EDTA) and
dye (Rhodamine 6G) can be used successfully in a photogalvanic cell. The conversion efficiency and
storage capacity of the cell is 1.26% and 170.0 minutes respectively, on irradiation for 150.0 minutes
developed photogalvanic cell. It has been observed that the micelles have not only enhanced the
electrical parameters (i.e. photopotential, photocurrent and power) but also the conversion efficiency
and storage capacity of photogalvanic cell. Photogalvanic cells can be used in dark whereas
photovoltaic cells cannot be used in dark. Photogalvanic cells have better storage capacity than
photovoltaic cells. So photogalvanic cells showed good prospects of becoming commercially viable.
NOMENCLATURE
ieq = photocurrent at equilibrium imax = maximum photocurrent
ipp = photocurrent at power point isc = short circuit current
ml = milliliter mV = millivolt
M = molarity pp = power point
t1/2 = storage capacity of cell DV = observed photopotential
Voc = open circuit voltage Vpp = photopotential at power point
η = fill factor mA = microampere
mW = microwatt

26
ACKNOWLEDGEMENT
The authors are grateful to The Head, Department of Chemistry, MLS University, Udaipur,
Rajasthan - 313001 (INDIA) for providing the necessary laboratory facilities to conduct this research
work. One of the authors (A.S.Meena) is thankful to Ministry of New and Renewable Energy
(MNRE), Government of India, New Delhi (INDIA) for the financial assistance to this research
work.
REFERENCES
[1] Rideal .E.K and Williams .E.G (1925), J. Chem. Soc. FaradayTrans., 127, 258-269.
[2] Rabinowitch .E (1940), J. Chem. Phys., 8, 551-559.
[3] Rabinowitch .E (1940), J. Chem. Phys., 8, 560-566.
[4] Potter .A.E and Thaller .L.H (1959), Solar Energy, 3, 1-7.
[5] Eliss .A.B and Kaiser .S.D (1976), J. Am. Chem. Soc., 98, 1117-1121.
[6] Rohatgi-Mukherjee .K.K, Roy .M and Bhowmik .B.B (1983), Solar Energy, 31, 417- 418.
[7] Dixit .N.S and Mackay .R.A (1982), J. Phys. Chem., 86, 4593-4598.
[8] Kamat .P.V (1985), J. Chem. Soc., Faraday Trans., 1, 509-518.
[9] Gratzel .M and Regan .B.O (1991), Nature, 353, 737-740.
[10] Albery .W.J and Archer .M.D (1977), Nature, 270, 399-402.
[11] Madhwani .S, Vardia .J, Punjabi .P.B and Sharma .V.K (2007), J. Power and Energy: Part A,
221, 33-39.
[12] Gangotri .K.M and Meena .R.C (2001), J. Photochem. Photobio. A. Chem., 141, 175-177.
[13] Genwa .K.R and Khatri .N.C (2006), Int. J. Chem. Sci., 4, 703-712.
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[15] Gangotri .K.M and Indora .V (2010), Solar Energy, 84, 271-276.
[16] Gangotri .K.M and Bhimwal .K.M (2011), Energy Sources, Part A, 33, 2104-2112.
[17] Bhati .K.K and Gangotri .K.M (2011), Int. J. Elect. Power & Energy Systems, 33, 155-158.
[18] Chandra .M (2012), Res. J. Pharm. Biological & Chemical, 3(2), 158-167.
[19] Chandra .M and Meena .R.C (2010), Int. J. Chemical Sciences, 8(3), 1447-1456.
[20] Chandra .M and Meena .R.C (2011), J. Chem. & Pharm. Research, 3(3), 264-270.
[21] Chandra .M, Singh .A and Meena .R.C (2012), Int. J. Physical Sciences, 7(42), 5642-5647.
[22] Joseph .A, Nagarajan and Mary .A (2013), Int. J. Electrical Engineering & Technology
(IJEET), 4(4), 205-212.
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Electrical Engineering & Technology (IJEET), 4(4), 180-187.

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