Efficiency definition of the deposition process of electrochromic Ni(OH)2-PVA films formed on a metal substrate from concentrated solutions

Abstract

Electrochemical devices based on nickel hydroxide electrodes are used in different areas. The main ones are chemical current sources, variable transparency “smart” windows, devices for carrying out electrocatalytic reactions, sensors for determining various substances. In this regard, methods of nickel hydroxide synthesis are of great interest, especially those that allow forming nickel hydroxide directly on the surface of electrodes. One of these methods is electrochemical deposition with cathodic current polarization. The available information on nickel hydroxide synthesis from nickel solutions was considered. It was shown that the available data mainly covered information on dilute solutions from 0.01 to 0.25 mol/L Ni(NO3)2. In addition, no comparison was found in the literature for the efficiency of the cathodic formation of Ni(OH)2 at different concentrations of nickel nitrate. To eliminate the lack of information, the dependence of the current efficiency on the concentration of nickel nitrate in the electrodeposition solution was determined at a constant cathode current density of 0.625 mA/cm2. The resulting dependence decreased nonlinearly with increasing concentration. The nickel hydroxide deposit formed in this case had an X-ray amorphous structure, and it depended little on the Ni(NO3)2 concentration. In addition, the current efficiency reached zero at concentrations of 1.5 mol/L Ni(NO3)2 and higher. However, with polyvinyl alcohol in the solution and at Ni(NO3)2 concentrations of 1.5 and 2 mol/L, electrochemically and electrochromically active Ni(OH)2 films were deposited. The current efficiency calculated indirectly for 1.5 and 2 mol/L Ni(NO3)2 solutions was 3.2 and 2.3 %, respectively. Thus, it was concluded that polyvinyl alcohol affected the mechanism of nickel hydroxide electrodeposition from aqueous solutions of nickel nitrate.

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

“…The authors researched the formation and study of the properties of electrochromic α-Ni(OH) 2 films on the surface of polished nickel [212][213][214][215][216] These works are aimed at the development of a smart mirror. The optimal temperature [213] and deposition time [214] were determined.…”

“…The poisoning effect of Al and Zn cations was revealed. The use of the Co 2+ additive resulted in the formation of a Ni−Co hydroxide film having two colors: bronze or copper‐bronze (in the intermediate‐colored state) and dark blue (in the fully colored state) (Figure 10 [215] ).…”

“…The poisoning effect of Al and Zn cations was revealed. The use of the Co 2 + additive resulted in the formation of a NiÀ Co hydroxide film having two colors: bronze or copper-bronze (in the intermediate-colored state) and dark blue (in the fully colored state) (Figure 10 [215] ). Multilayered electrochromic films based on nickel and cobalt hydroxides were obtained, [216] and the efficiency of the deposition process was evaluated.…”

“…The optimal temperature [213] and deposition time [214] were determined. In, [215] a film was obtained with the addition of Al, Zn, and Co ions. The poisoning effect of Al and Zn cations was revealed.…”