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Oxidation of the iodide ion is an important facet of the solar cells such as perovskite solar cells and dye-sensitized solar cells. The rate of reaction undoubtedly depends upon several factors. Such parameters include reaction media, electrolyte, and the nature of solvents, and electrolyte. If these factors are optimized then the rate of the reaction can be controlled and could be used to get the maximum benefit out of it such as economically and industrially cost-effective uses of the reaction and globally environmentally benign. We studied the kinetics of the oxidation of the iodide ion in the binary solvent system that consisted of 10% (v/v) tertiary butyl alcohol and water. The transition metal complex such as dicyanobis(phenanthroline)iron(III) oxidizes the iodide ion spontaneously without any external triggering with a fast rate at 293 ± 1 K. The reaction was probed under the pseudo-first-order condition with an excess concentration of the iodide ion over dicyanobis(phenanthroline)iron(III) at 0.06 M ionic strength. The reaction was observed independent of the concentration of dicyanobis(phenanthroline)iron(III), that is, the zero order and third order with respect to the iodide ion in the selected solvent system. An overall third-order was observed for the redox reaction. The value of the multiplication product of the molar absorptivity (ɛ), path length of the cuvette (b), and overall rate constant (k) was deduced to be 1.59 × 10 6 M −3 s −1. The observed zero-order rate constant of the reaction was increased by the fractional (1.5) power of the concentration of protons in the excess concentration of acid 1 mM to 0.1 M. The multiplication product of ɛ⋅b to the fractional order rate constant (k′) was found 0.773 M −1.5 s −1 that confirms protonation of triiodide in acidic-10% (v/v) tertiary butyl alcohol-water. The effect of ionic strength showed a similar impact in different compositions of solvents such as 5, 10, and 20% (v/v) tertiary butyl alcoholwater. The observed zero-order rate constant was decreased upon increasing the ionic strength in each medium consisting of the binary solvent system.

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Dye-sensitized solar cells (DSSCs) are a technically and financially viable alternative to today’s photovoltaic systems using p-n junctions. The two functions are isolated here, which are unlike traditional systems where the semiconductor is thought to perform both light absorption and charge carrier transport. This article discusses the potential use of dicyanobis(bipyridine)iron(III) to oxidize iodide as a sensitizer in DSSCs. However, it is critical to understand the kinetics of this essential process in order to understand the mechanism of electron transport. The oxidation of iodide by dicyanobis(bipyridine)iron(III) in three reaction media was studied: water, 10% v/v 1,4-dioxane-water, and 20% v/v 1,4-dioxane-water. The reaction was carried out in a regular laboratory setting, with no special sensitive conditions or the use of expensive materials, making it a cost-effective and practical method. Dicyanobis(bipyridine)iron(III) oxidized iodide in selected media at 0.06 M ionic strength and constant temperature. The reaction was subjected to a spectrophotometric analysis. The data were acquired by measuring the rise in visible absorbance as a function of time after the formation of dicyanobis(bipyridine)iron(II). The reaction proceeded with an overall fractional (0.5), first order, and third order in water, 10% media, and 20% media, respectively. The presence of dicyanobis(bipyridine)iron(III) in either of the reaction media had no effect on the rate. The effect of protons (H+) on the rate constant indicated resistance in water and catalysis in dioxane-water media containing 10–20% dioxane. When the ionic strength was raised, there was no change in the rate constant in water, but there was a deceleration in both binary solvent media. In an aqueous medium, the thermodynamic parameters of activation were computed as Ea 46.23 kJ mol−1, 24.62 M s−1, ΔH# 43.76 kJ mol−1, ΔS# −226.5 J mol−1 K−1, and ΔG# 111.26 kJ mol−1 (25 °C). By increasing the rate of the reaction to its maximum, this study discovered the binary solvent media with the highest catalytic efficiency, i.e., 20% v/v 1,4-dioxane-water, which may increase the efficiency of DSSCs without using any expensive material or unusual experimental conditions.