Background: Demands of rechargeable energy storage devices such as batteries are increasing. Potassium is cheap and abundant contrary to Li. Prussian blue and analogues PBAs are promising cathodes materials for K- ion batteries, because of facile synthesis and low cost. However, PB and close analogues (Prussian green and Prussian white) suffer from low coulombic efficiency and low cyclability owing to structure deficiency. We present here a facile synthesis dip-dry method at elevated temperature of Prussian yellow film cathode for aqueous potassium battery with Zn anode. The device exhibits a high specific capacity, coulombic efficiency and long cycling life with satisfactory charge/discharge behavior. Method: Prussian yellow(PY) film was prepared as a thin film on ITO substrate by dip dry method from a solution mixture of Fe3+ (0.1M) and Fe(CN)-6 (0.1M) at (80°C). Precipitation time was fifteen minutes. Films where characterization by FTIR, TGA, XRD, EDS, SEM, CV and EIS. Batteries composed of PY cathode and zinc metal anode were tested in 0.1M KCl electrolyte. Results: Battery gave OCV 1.9V with specific capacity of 142 mAh/g at rate of (~ 3C), with satisfactorily cycling ability up to 500 cycles & reversible charge/discharge behavior. Good crystal structure of PY film was demonstrated by several characterization methods e.g., FT-IR, TGA, XRD, EDS, SEM and electrochemical techniques. All showed good crystallinity quality of prepared PY films which demonstrate cathode qualities K cathode for K charge / discharge battery. Conclusion: Prussian yellow film, one of Prussian blue close analogues prepared in a simple and very facile nonelectrical method can be used as a robust cathode with highly reversible redox reactions that enable this material to be used as a cathode in battery of potassium aqueous electrolyte with Zinc anode. Battery has a significant cycle life (~500 cycle) and satisfactory capacity of 142mAhg-1 at rate of (~3C) with efficiency retention of 82%.

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Aim: Construction of electro chromic device via Prussian yellow Nano film on glass electrode. Background: Energy conservation in one of the most primary research topics nowadays. Electro chromic device with low power consumption and short stable switching periods, are well suited to energy efficient applications, e.g. smart windows, car mirrors, displays, and electronic papers. Objective: Preparation of electro chromic nano Prussian yellow film on ITO glass by a simple chemical facile method and study of its electro chromic features Methods: Prussian yellow film (iron (III) hexacyanoferrate (III)), was prepared by immersing substrate in a solution of ferric nitrate and Potassium hexacyanoferrate. Prussian Yellow film was characterized by ultraviolet-visible (Uv-vis) spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. Prussian yellow film, shows an intense yellow color when it is in pristine state. Results: Resultant Prussian yellow film underwent reversible redox reactions accompanied with color changes from Prussian yellow to Prussian green to further Prussian blue then to Prussian white. Transmittance of Prussian yellow film varies from 21% for colored state at 450nm to 81 % (for fully bleached) at 0.9V. Contrast ratio and ratio of optical density to charge density were examined. The coloration efficiency was be calculated to be 299.6 cm2C-1. Conclusion: Prussian yellow can be very simply prepared and used as an efficient fast switching electro chromic device with high color contrast.