Electrochemical Properties of a Ferrocene-Containing Poly(vinyl alcohol)-Based Redox Hydrogel and Its Application as a Matrix for Electrochromic Devices

Abstract

For the creation of novel electrochemically active redox hydrogel materials, this study developed a novel redox-active hydrogel for wearable electronics by incorporating a ferrocene/hydroxypropyl-β-cyclodextrin (Fc/CD) inclusion complex into a poly(vinyl alcohol) (PVA)/borax-based gel at various ratios. A systematic evaluation revealed that despite their pseudo-thixotropic behavior and soft gel nature, the resulting hydrogels maintained the chemically reversible electrochemical characteristics of Fc. Moreover, the hydrogels demonstrated electrochemical reversibility in a hydrogel midium, particularly under slow potential sweep conditions. This synthesized hydrogel was used as an electroactive matrix to fabricate a single-layer gel-based electrochromic device containing methyl viologen dibromide as the electrochromic molecule. The device displayed distinct color changes upon voltage application, thereby confirming its electrochromic functionality. These findings demonstrate that the developed redox hydrogel functions effectively as a redox-active matrix for electrochemical devices, with significant potential for advanced applications in electrochemical and wearable technologies.