Definition of the influence of pulsed deposition modes on the electrochromic properties of Ni(OH)2-polyvinyl alcohol films

Abstract

In this work, the influence of some types of the pulsed deposition mode of electrochromic films from aqueous solutions of nickel nitrate with the addition of polyvinyl alcohol was investigated. Glass coated with a fluorine-doped tin oxide film was used as the basis for deposition. The deposition of nickel (II) hydroxide – polyvinyl alcohol electrochromic films was carried out in three pulsed modes: –0.2 mA/cm2×5 s, 0 mA/cm2×5 s (10 minutes); –0.5 mA/cm2×2 s, 0 mA/cm2×8 s (10 minutes); –1 mA/cm2×1 s, 0 mA/cm2×9 s. In this case, the amount of electricity used for the formation of thin-film electrodes was the same for all samples. The resulting films showed dramatic differences in electrochemical, optical, and quality characteristics. The sample obtained in the mode of the highest cathode current density and the duration of the no-current condition (1 mA/cm2×1 s, 0 mA/cm2×9 s) had the worst specific capacity and optical characteristics. This sample was characterized by the highest number of coating defects and color non-uniformity as well. The sample, which was obtained at average current densities (–0.5 mA/cm2×2 s, 0 mA/cm2×8 s), had the highest specific characteristics among the electrodes in the series. The coating was uniform and solid. Also, this sample had the greatest stability of the coloration depth value, which varied from 79.1 to 78.1 % (first to fifth cycles). The sample obtained in the mode –0.2 mA/cm2×5 s, 0 mA/cm2×5 s showed moderate specific indicators, however, there were some coating defects. According to the results obtained, a mechanism was proposed that explained the differences in the characteristics of thin-film electrodes formed in different modes. This mechanism consists of changing the time of non-stationary processes and the distribution of the current density with a change in the value of the deposition current density, the duration of the cathode period, and the no-current condition.

Nickel Hydroxides: Requirements, Targeted Construction and Choice of Characteristics and Industrially Applicable Synthesis for Targeted Use in Electrochemical Devices

“…[217] Several investigations of the formation and research of electrochromic nickel hydroxide films deposited on glass with an electrically conductive layer were also carried out for ITO [218] and FTO. [219][220][221][222][223][224][225][226][227][228][229][230][231][232][233] To increase the adhesion of the hydroxide film to FTO, the soft electrochemical etching method was developed. [219] The use of low concentrations of nickel nitrate and cathodic current density for cathode template synthesis was substantiated by the method of mathematical computer simulation.…”

“…[224] To improve the characteristics of nickel hydroxide films, it was proposed to use activating additives of tungstate anion, [225,227] aluminum, [226,227] and manganese [226,228] cations. Optimization of electrolyte composition [229] and the deposition conditions [230] was carried out. It was proposed to use for cathode template synthesis by pulsed current mode.…”

“…Several investigations of the formation and research of electrochromic nickel hydroxide films deposited on glass with an electrically conductive layer were also carried out for ITO [218] and FTO [219–233] . To increase the adhesion of the hydroxide film to FTO, the soft electrochemical etching method was developed [219] .…”

Definition of the role of polyvinyl alcohol during formation and in the structure of cathodic synthesized composite electrochromic nickel hydroxide layer: template or surfactant

“…In [31], it was proposed to use template synthesis with PVA to obtain a Ni(OH) 2 film with high electrochromic properties and adhesion to the substrate. Experiments were carried out to investigate the influence of the preparation modes (temperature [53], time [54], and pulse-type [55] formation) and composition of the electrolyte (template concentration [56] and effect of tungstate anion as an activator [57]). In the described works, highly active electrochromic films with good adhesion were synthesized.…”