With the rapid commercialization of solar and wind power as supplements and potential substitutes of fossil fuels, the need for power storage techniques to render renewable energy sources impervious to climatic variations has gained significant importance recently. In addition to this requirement of power storage, photo-galvanic (PG) cells hold special significance because these photo-electrochemical devices are capable of simultaneous solar power generation and storage. PG cells with performance as high as 649.6 mW power (P pp ), 2250 mA current (i sc ), 1048 mV potential (V oc ), 8.12% conversion efficiency (CE), and 59 minutes power storage capacity (as half-time, t 0.5 ) have been reported under artificial and low illumination intensities. To enable PG cells, a future source of solar energy conversion, with storage as well, their efficiency must be improved further to a level comparable to that of photovoltaic cells. The metanil yellow dye (photo-sensitizer)-formic acid (reductant) couple has not been exploited to date for this purpose. Therefore, in the present study, the metanil yellow dye as a photosensitizer and formic acid as a reductant have been used in the presence of sodium lauryl sulfate surfactant and sodium hydroxide alkaline medium to further increase the solar energy conversion efficiency and storage capacity of PG cells. The present study reports greatly enhanced electrical performance (compared to earlier results for similar cells) of P pp 822 mW, i sc 6000 mA, V oc 1110 mV, CE 20.41%, and t 0.5 105 minutes. On the basis of the redox potential and reported data, a plausible mechanism has also been proposed for the photo-generation of current in metanil yellow-formic acid photogalvanics. ; Tel: +91 291 2614162 † Electronic supplementary information (ESI) available. See

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The photogalvanic cells (PG) are the promising and renewable electrochemical energy devices capable of doing the simultaneous solar power generation and storage. To realize the aim of the practical application of the PG cells in daily life, the electrical output of these cells has to be further enhanced to a level at least comparable to that of the photovoltaic cells. The present study of the PG cells based on so far unexplored Congo red dye-formaldehyde as a photosensitizer-reductant couple along with efficiency enhancer surfactant reagent (sodium lauryl sulfate) in the sodium hydroxide alkaline medium has shown greatly enhanced cell performance over published results. The present study has shown electrical cell performance of the PG cell as Ppp 782 μW, isc 3200 μA, Voc 1074 mV, and CE 11.02% at artificial and low illumination intensity. The storage capacity (t0.5) of the PG cell has been observed in the present study as 120 min in the dark. The study of variation of the different cell fabrication parameters has shown optimum cell performance at an optimal value of these cell fabrication parameters. The most plausible mechanism of the photo-generation of the current in PG cells is also proposed on the basis of observed potential values and published literature.

Photogalvanicists have conventionally used complicated, multichambered, sophisticated, and very costly cell designs for solar electricity and storage. We authors have simplified cell design with encouraging electrical output as well.We authors have used a simple, cheap, and one-chambered cell design based on cylindrical glass tubes instead of the costly, conventional, and complex Hshaped glass tube-based cell fabrication design. The study has been done under similar electrolytic and illuminating conditions for different cell designs based on various blackened H-shaped glass tubes of the different diffusion lengths, nonblackened simple glass boiling tube, blackened simple glass boiling tube, and simple noncoated glass beakers. Nonblackened glass tube-based cell design has shown very good electrical output, that is, power 439 μW, current 2100 μA, potential 1045 mV, efficiency 6.1%, and storage capacity 130 minutes. Under similar chemical and illuminating conditions, the electrical output of cells fabricated of the simple glass tube is as good as that of the conventional cells made from the complex H-shaped glass tube. Furthermore, the cell design based on a simple cylindrical glass tube is three-edged more advantageous (in terms of the cost, electrical output, and ease of fabrication) over all other cell designs reported so far.

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