Significance of surface roughness in the supercapacitor activity of nickel-based electrodes

Nickel-based thin film electrodes were electrodeposited onto copper substrate using a deep eutectic solvent. The supercapacitor performance of these electrodes in alkaline KOH solution was greatly enhanced by altering surface roughness of coatings. In order to create a rougher surface, two paths were followed. In the first path, Ni-only coatings were prepared at different deposition potentials and smooth-to-rough transition in surface morphology took place at higher potentials due to increasing emission of hydrogen bubbles. In the second path, Ni-Zn binary coatings with varying zinc concentration were electrodeposited and surface roughness was formed by dealloying zinc element from the electrodes as corroborated by Scanning Electron Microscopy and Atomic Force Microscopy results. In both paths, noticeable improvements in the capacitance of nickel electrodes were observed upon the apperance of rougher surface. A linear relationship was discovered between cathodic peak currents and polarization values in the cyclic voltammetry scans of electrodes, possibly for the first time here in literature. The increase in polarization was explained by the decrease in electrode conductivity proved by dwindling of metallic nickel peaks in X-ray diffraction upon electrochemical testing.

Automated summary

In this study, nickel-based thin film electrodes were electrodeposited onto copper substrate using a deep eutectic solvent, and their supercapacitor performance in alkaline KOH solution was greatly enhanced by altering the surface roughness of coatings. Two approaches were taken to create a rougher surface: preparing Ni-only coatings at different deposition potentials and electrodepositing Ni-Zn binary coatings with varying zinc concentration. Both approaches led to noticeable improvements in the capacitance of nickel electrodes. The linear relationship discovered between cathodic peak currents and polarization values in cyclic voltammetry scans of electrodes suggests a potential novel finding in the literature.