Elsevier

Renewable Energy

Volume 37, Issue 1, January 2012, Pages 250-258
Renewable Energy

Solar energy conversion and storage: Rhodamine B - Fructose photogalvanic cell

https://doi.org/10.1016/j.renene.2011.06.022Get rights and content

Abstract

Photogalvanic cells are photoelectrochemical cells chargeable in light for solar energy conversion and storage. They may be energy source for the future, if their electrical performance is increased. In this study, the Rhodamine B dye as photo sensitizer, Fructose as reductant and NaOH as alkaline medium has been used to enhance electrical performance of the cell. The observed cell performance is radically high. The observed cell performance in terms of maximum potential, maximum photocurrent, short-circuit current, power at power point, conversion efficiency and storage capacity in terms of half change time is −1071 mV, 1049 μA, 972 μA, 244.02 μW, 7.58% and 3.6 h, respectively. It is concluded that Rhodamine B - Fructose based cells have radically enhanced performance. It is also viewed that the Rhodamine B - Fructose based photogalvanic cells, with additional advantage of low cost and storage capacity, can give electrical output comparable to that for commercially used power storage property lacking photovoltaic cells.

Highlights

► Rhodamine B dye-Fructose were studied for enhancing performance of cell. ► Observed short-circuit current and power are 972 μA and 244.02 μW, respectively. ► The obtained results are highly encouraging. ► Rhodamine B dye – Fructose system enhances performance of cell. ► The results are comparable to that for photovoltaic cells.

Introduction

Solar energy is a cheap, clean, abundant and freely available renewable non-conventional source for power generation. Photogalvanic cell technique provides a promising and unexplored method for solar power generation and storage. Photogalvanic cell is a photoelectrochemical device involving ions as mobile charges moving in solution through diffusion process. In this cell, the solution is absorber phase contacted by two electrodes with different selectivity to the redox reaction. The current or voltage changes results from photo chemically generated changes in the relative concentrations of reactants in a solution phase redox couple. Alternatively, it can be said that in a photogalvanic cell, a dye in solution is photo excited to energy rich product which may lose energy electrochemically to generate electricity with inherent storage capacity. The inherent storage makes them superior to photovoltaic cells. There is no consumption of chemicals during charging and de-charging of these solar cells.

First of all, Rideal and Williams [1] observed the photogalvanic effect during the action of light on the ferrous iodine–iodide equilibrium, which later on was systematically investigated by Rabinowitch [2], [3] in Fe (II)-Thionine system. Rabinowitch suggested that the photogalvanic effect might be used to convert sunlight into electricity. To explore this suggestion, some photogalvanic cells using the iron-thionine system as the photosensitive fluid were tested [4]. The observed maximum power conversion efficiency was 3 × 10−4 per cent. The principal reason for the low efficiency was shown to be polarization of the polished platinum electrodes and rapid loss of the photochemical activity of the dye. Coating the electrodes with platinum black reduced polarization sufficiently. In principle, it appeared possible to make further increases in efficiency by increasing electrode area and decreasing the electrolyte resistance.

The maximum power conversion efficiency [5] that could be achieved from a photogalvanic cell is between 5 and 9%.

Photogalvanic cells based on Chlorophyll-a (Chl-a) plated Pt electrode and Chl-a free Pt electrode separated by a salt bridge [6], aqueous ferric bromide [7], ruthenium complex of dye [8], [9], [10], [Cr2O2S2(1-Pipdtc)2(H2O)2] in a Honda Cell [11], and micro emulsions with micellar solution [12] have also been studied. Gangotri and Pramila [13] have presented principles of photogalvanic cell containing NaLS, mannitol (reductant) and safranine (photo sensitizer) in which compounds are broken up by sunlight into electrochemically charged fragments which usually recombine instantaneously if relieved of their electrical charges.

In beginning, photogalvanics emphasized on coated Pt electrode with Fe2+ as reducing agent. Later on, the researcher started using non-coated Pt electrode with saturated calomel electrode, dyes like methylene blue [14], [15], azure-B [16], azure-A [17], fluoroscein [18], toluidine blue [19], malachite Green [20], etc., organic reductants like mannitol [21], oxalic acid [22],ethylene diamine tetraacetic acid [23], etc. and surfactants like sodium lauryl sulfate (NaLS) [24], [25].,Tween-80 [26], etc.

The literature survey reveals that electrical parameters of photogalvanic cells are low. So, the use of suitable photo sensitizer with reductant in photogalvanic cells is needed for higher electrical output. Therefore, with aim of getting higher electrical performance of photogalvanic cell, the use of Rhodamine B with D(−) Fructose, Saturated calomel electrode (of combination electrode) and Pt electrode of very small area was planned. Fructose was chosen as reducing agent due to its widely known good reducing property in rapid Furfural test.

Section snippets

Chemicals

Chemicals, Rhodamine B (90% Assay-Purity, Ases Chemical Works, Jodhpur, India) as photo sensitizer, Fructose (99.8% Assay-Purity, Ases Chemical Works, Jodhpur, India) as reductant, NaOH (98% Assay-Purity, Ases Chemical Works, Jodhpur, India) as alkaline medium, and Oxalic Acid (99.5% Assay-Purity, Rankem, New Delhi, India) for standardization of NaOH with Phenolphthalein (Merck Specialties Pvt. Ltd., Mumbai, India) as indicator have been used.

Characteristics of Rhodamine B dye are M.F. C28H31Cl

Mechanism of photocurrent generation and storage capacity

The photo potential and photocurrent generation in photogalvanic cell can be explained by following mechanism [13].

Variation of photo potential, current and power

A photogalvanic cell consisting of 1.8 mL of M/1000 Rhodamine B dye, 1.4 mL of M/100 Fructose, 4.4 mL of 1M NaOH and 17.4 mL of doubly distilled water (to make total volume of solution 25 mL) has been studied. The specifications for this cell are [Rhodamine B] = 7.2 × 10−5 M, [Fructose] = 5.6 × 10−4 M, pH = 13.24, light Intensity = 10.4 mW cm−2, temperature = 310 K, diffusion length (DL) = 45 mm, and Pt electrode area = 0.4 × 0.2 cm2.

On illumination of photogalvanic cell, the potential

Conclusion

The results so observed for Rhodamine system are relatively very high. These results shall encourage photogalvanicists world over to put efforts toward practical applicability of eco-friendly and cost effective photogalvanic technique.

The reasons for high results for Rhodamine B(dye) - Fructose system may be found in peculiarity of its construction, use of Pt electrode of very small area, use of Pt electrode scratched and cleaned with the help of hot solder, use of SCE of combination electrode,

Author Contributions

Prof. K.M. Gangotri guided the research work and writing of this manuscript. Urvashi Sharma and Pooran Koli jointly carried out research work in lab and prepared this manuscript. All authors discussed the results and commented on the manuscript.

Competing financial interests

Authors have no competing financial interests.

Acknowledgments

The authors are thankful to Department of Chemistry, J.N.V. University, Jodhpur, Rajasthan (INDIA) for providing all necessary laboratory facilities and pleasant environment for research.

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