Electrochromic cell with hydrogel-stabilized water-based electrolyte using electrodeposition as a fast color changing mechanism

Highlights: • Electrochromic device that uses electrodeposition of lead (II) oxide. • N,N-dimethylacrylamide (DMAM) and N-isopropylacrylamide (NIPAM) hydrogel-stabilized water-based electrolyte. • High speed response time of 15 s between bleached and tinted state of the devices. A new type of electrochromic device that uses electrodeposition of lead(II) oxide in combination with hydrogel-stabilized water-based electrolyte has been investigated. Operation of selected devices was examined using a series of electrochemical techniques (cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy), along with UV–Vis transmittance spectroscopy. Presented devices with use of electrodeposited PbO from aqueous solution exhibited very short response time of 15 s. Data obtained from experiments showed high difference between bleached and tinted state while low potential required for color change (+1.7 V). All tested devices were unsealed and performed electrochromic effect for several cycles with unchanged repeatable cycling ability. Best characteristics, achieving good repeatability, high transmittance in bleached state and good coloration in tinted state, along with good stability, were obtained with device using a cross-linked random copolymer hydrogel N,N-dimethylacrylamide (DMAM) and N-isopropylacrylamide (NIPAM) with a 85:15 unit molar ratio (DMAM/NIPAM), in combination with water-based Pb²⁺/Ni²⁺ electrolyte and PbO as working electrode and NiO as counter electrode. Constructed devices showed stable color in tinted state and ability to self-bleach when short-circuited. This type of electrochromic cells could be used as a more time-stable and lower cost alternative for existing intercalation-type electrochromic devices.