Abstract
Nickel foam is widely used as a current lead/current collector and the basis of nickel hydroxide electrodes for various electrochemical devices – batteries, hybrid supercapacitors, devices for electrocatalytic oxidation of organic substances. The characteristics of commercial samples of nickel foam produced by Novomet-Perm (Russian Federation) obtained by electroless and then electrochemical nickel plating and Linyi Gelon LIB Co Ltd (China) obtained by electroless nickel plating were studied. The nature of passivity was determined by forming model samples of electrochemical and electroless nickel on a steel base. For the passive sample, activation was carried out by applying a layer of electrochemical nickel from an impact nickel plating solution. Activated, non-activated samples of nickel foam, as well as model samples, were studied by the methods of cyclic voltammetry and galvanostatic charge-discharge cycling in the supercapacitor mode. Comparative analysis of Chinese-made and Russian-made nickel foam samples showed significant passivity of the former – in cyclic voltammetry, the activity was 4.8 times lower, with galvanostatic charge-discharge cycling – 2.59 times lower. It was suggested that high passivity was determined by the fact that the sample consisted of Ni-P or Ni-B alloy. This assumption was proved by the method of natural simulation. The electrochemical activity of electroless nickel was 1.25 times lower than that of electrochemical nickel (according to cyclic voltammetry data) and 1.58 times lower (according to galvanostatic cycling data). For the first time, Chinese-made nickel foam (electroless nickel) was activated by applying a layer of electrochemical nickel from an impact nickel electrolyte. The high activation efficiency was shown as follows – on the cyclic curve, the specific current of the anodic peak increased 8.71 times, and with galvanostatic cycling, the increase in specific capacity was from 1.73 times (at i=120 mA/cm2) to 4.84 times (at i=20 mA/cm2)
Highlights
Supercapacitors (SC) are promising chemical current sources (CСS)
Supercapacitors are characterized by a high charge-discharge rate
At the Faraday electrode of the hybrid supercapacitor, the electrochemical process occurs on the surface and in the thin surface layer of the active substance particles
Summary
Supercapacitors (SC) are promising chemical current sources (CСS). SC are widely used to start various types of electric motors in electric vehicles, pumping stations, power tools, and other devices. Promising is the use of nickel foam as a current collector for a nickel oxide electrode and a current collector – the basis of a pasted nickel oxide electrode for electrocatalytic oxidation of organic substances [18]. This is because the nickel surface is covered with a thin layer of nickel oxide, which, in an alkaline medium, transforms into electrochemically active nickel hydroxide. Nickel foam samples can be obtained by various methods, and the surface oxide layer can be highly passivated. Determining the surface activity of nickel foam and the ways of its activation is an urgent task
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