Study of KOH as alkali for enhancing performance of photo-galvanic cell in transparent cylindrical cell design.

Photo-galvanic cells are liquid electrolyte-based dye-sensitized solar cells. Chemically, the dye/pigment photo-sensitizer, reductant, surfactant, and alkali materials are the main fabrication components of these cells. Most dye/pigment materials are more soluble and stable at high pH. The pH of Potassium hydroxide (an alkali of plant nutrient 'potassium' element) is very high. Therefore, Potassium hydroxide is supposed to be the best eco-friendly and effective alkali medium for photogalvanics. As far as alkali is concerned, NaOH has been exploited extensively in photo-galvanics. Although, the NaOH-based photo-galvanics show good electrical output, it is plagued with some drawbacks like shorter shelf life, high cost, unsafe for skin, low conductivity, low water solubility, etc. Therefore, in the present research, the KOH has been exploited as an alkali material for harvesting solar energy using the Sunset Yellow FCF dye sensitizer-Ascorbic acid reductant-CTAB surfactant cylindrical cell designed photo-galvanic system. In the present study, the observed optimum cell performance is as follows-open-circuit potential 777 mV, maximum current 25000 µA, short-circuit current 5600 µA, power 733.6 µW, fill factor 0.16, and efficiency is 19.77 % at pH 14.30. The Sunset Yellow FCF dye shows very high photostability and photo-absorption with KOH alkali. The power storage capacity is sufficiently robust, as the cell is capable of supplying power at its ∼36.16 % capacity after a very long time of 24 h. The KOH-Sunset Yellow FCF dye sensitizer-Ascorbic acid reductant-CTAB surfactant photo-galvanics in the present study show improved results over the reported results for the NaOH-Sunset Yellow FCF dye sensitizer-Ascorbic acid reductant-CTAB surfactant photo-galvanics. The reasons for the good photo-galvanics with KOH alkali may be attributed to some peculiar chemical and physical properties of KOH vis-à-vis the chemical and physical properties of NaOH.

Photogalvanics of copper and brass working electrodes in the NaOH-Allura Red-d-galactose-DDAC electrolyte for solar power generation.

Solar energy is a limitless energy resource that can be used to produce electricity forever. Photogalvanic cells can convert solar energy into electricity with inherent power storage. The electrolyte(s) and a combination of two electrodes are the main materials required for fabrication of these cells. So far, platinum has been used as the working electrode in photogalvanic cells. Platinum is an extremely rare and expensive metal. Copper and its alloy (brass) have been identified as alternative working electrodes to substitute the platinum working electrode in photogalvanic cells. In addition, copper and brass utilization is identified to be an effective, user-friendly, and safe approach for high-power generation. Therefore, in the present work, cheap and easily obtainable copper and brass (alloy of copper and zinc) working electrodes have been exploited with the twin aim of high-power generation with less input cost. In the present study, the observed power, current, potential, and efficiency for the copper electrode are 552.3 µW, 4030 µA, 713 mV, and 8.54%, respectively, and those for the brass electrode are 546.4 µW, 5320 µA, 739 mV, and 6.12%, respectively. The observed electrical performance is greatly enhanced compared to most of the already reported photogalvanics with platinum electrode. Copper and brass are slightly and slowly corroded by the alkali, but despite this electrode loss, both materials are promising to produce the highest power. In the future, this electrode loss can be checked by using inhibitors.

Characterization, stability, and feasibility of long-term use of light-absorbing components of aqueous spinach extract-based photogalvanic electrolyte.

In the present work, the photogalvanic cells have been studied with respect to the photo-stability and the long-term use of the electrolyte based on crude aqueous spinach extract sensitizer for solar energy harvesting. Further, the nature of chemical components present in the old and photo-decayed electrolyte and their current generation capacity has also not been investigated so far otherwise it is of much significance for durable use of the same electrolyte in cells. In earlier studies, the steady-state photo-generation of current for about two hours from crude spinach extract-based cell has been shown during illumination. But, the data for only two hours of the steady-state current generation is not sufficient to show the feasibility of working with photogalvanic cells. Therefore, to fill this research gap of lack of characterization of sensitizers' molecules of crude spinach extract and lack of study on long-term use of this electrolyte (crude spinach extract-surfactant-reductant-alkali-water), the present extensive study has been done. The observed spectrum of crude spinach extract resembles that of chlorophyll-protein complex showing it is the main chemical component in extract absorbing light. A strong acid adversely affects the extract's photogalvanics and high pH is friendly to the physiological and photogalvanic activity of the extract. The spectra of illuminated and very old crude spinach extract-NaOH-Sodium lauryl sulfate (NaLS)-Fructose photogalvanic electrolyte solution show negligible absorbance (540-700 nm) and zero absorbance (at 700 nm) suggesting the absence of chlorophyll due to its photo-degradation. When this photo-degraded electrolyte is again illuminated, the power output obtained is nearly equal to that for the first time illuminated fresh electrolyte. The observed current at zero time and after 2641 h from the same electrolyte used in long term is 50 mA cm-2 and 40 mA cm-2, respectively. It means that the fresh crude spinach extract, as well as the photo-degraded extract at high pH, are almost equally capable of power generation.

Use of Congo red dye-formaldehyde as a new sensitizer-reductant couple for enhanced simultaneous solar energy conversion and storage by photogalvanic cells at the low and artificial sun intensity.

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.

Simultaneous electrochemical solar power generation and storage using metanil yellow-formic acid as a new sensitizer-reductant couple in photogalvanic cells.

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 µW power (P pp), 2250 µA 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 µW, i sc 6000 µA, 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.