Smart windows: cation internal and anion external activation for electrochromic films of nickel hydroxide

Abstract

Two methods - internal and external - were used for improving the electrochemical activity and electrochromic properties of Ni(OH)2 films. In the case of internal activation, Al3+ ions were added to the electrolyte composition during the electrochemical precipitation process. In the case of external activation, [Fe(CN)6]4− ions were used in the electrolyte during the cycling process. In all the experiments there were used Ni(OH)2 films synthesized by the electrochemical template method with polyvinyl alcohol (PVA) addition to the electrolyte composition. It was shown that the addition of [Fe(CN)6]4− ions into the electrolyte for cycling leads to significant improvement of electrochemical and electrochromic (colorization-bleaching) properties. At the same time, the addition of Al3+ ions into the electrolyte for Ni(OH)2 films precipitation leads to drastic worsening of their properties. Also, possible mechanisms of Al3+ and [Fe(CN)6]4− ions influence were considered in this work.