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.

Highlights

  • Nickel hydroxide (Ni(OH)2) has been widely used in various electrochemical systems due to its unique properties

  • The study aimed to determine the efficiency of the processes of nickel hydroxide electrodeposition from concentrated nickel nitrate solutions

  • The aim was to solve a number of problems: – to determine the current efficiency and structural characteristics of nickel (II) hydroxides obtained at high concentrations of nickel nitrate; – to determine the electrochemical and electrochromic characteristics of the resulting nickel (II) hydroxide deposit from solutions with increased concentration

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Summary

Introduction

Nickel hydroxide (Ni(OH)2) has been widely used in various electrochemical systems due to its unique properties. 6/12 ( 114 ) 2021 of the capacitance of the reversible electrochemical reaction of the Ni(OH)2/NiOOH pair and the charge capacitance of the double electric layer The latter is determined by the specific surface area of nickel (II) hydroxide. Hydroxide-oxide nickel films formed by different methods [8] are widely used as electrochromic coatings [9] These coatings can reversibly change their optical characteristics since nickel hydroxide in thin layers is transparent and transforms into a dark brown oxyhydroxide NiOOH upon oxidation with an electric current [10]. Nickel oxide electrode is positioned as an element of electrochemical cells for oxidation from organic wastewater contamination [11] This application is due to the fact that, during anodic polarization, a constantly renewable film of an active electrocatalyst for oxidation is formed. Considering all the variety of forms and purposes of application, it can be argued that the study of Ni(OH) production methods is an important research task

Literature review and problem statement
The aim and objectives of the study
Research materials and methods
Results of electrochemical and electrochromic
Conclusions
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