Mesophase micelle-assisted electrodeposition and magnetisation behavior of meso-porous nickel films for efficient electrochemical energy and magnetic device applications

Abstract

Mesoporous magnetic materials have found interesting potential applications in electrochemical energy harvesting and energy-efficient magnetic actuation device applications. Here we report on the electrodeposition and magnetic properties of mesoporous nickel films from lyotropic liquid crystal (LLC) templates formed by cetyltrimethylammoniumbromide (CTAB) cationic surfactant. Diffusion-controlled electrodeposition mechanism of nickel is determined. Films are electrodeposited under a constant current ranging from 1 to 7.5 mA cm−2 from an aqueous solution containing 0.1 M nickel sulphate, 0.2 M boric acid solution and CTAB with a concentration ranging from 0 to 50 wt.%. Mesopores develop an arranged hexagonal structure due to the micellar positional and orientational order reaching its highest value at 30 wt.% of CTAB at 2 mA cm−2. This is confirmed by transmission electron microscopy (TEM) and electrocatalytic surface area measurement. Electrodeposition current density and pH modify the mesoporous dimensions and therefore the magnetic properties change, tough hydrogen evolution as a side reaction influences the mesoporous structure. We observe an increased in-plane magnetic coercivity value to a maximum of 214 Oe for the mesoporous nickel film, which correlates with the increased interaction field. The widening of the coercivity distribution in first-order reversal curve (FORC) diagrams indicates that films with higher CTAB content have more inhomogeneous structure, which can lead to complex magnetization reversal mechanisms. The results of this study will help to exploit novel multifunctional magnetic and electrochemical energy materials and devices.