Porous Nickel Nano-Foam by Femtosecond Laser Structuring for Supercapacitor Application

A focused femtosecond laser beam was scanned across a nickel electrode in a line pattern with different line distances to generate a large electrochemical surface area for charge storage. During the laser structuring process, small metal particles were generated and sintered to a porous foam-like structure, the so-called laser-induced nano-foam (LINF), which strongly adheres to the substrate surface. The structuring was carried out in argon atmosphere, in order to prevent oxidation of the LINF structure during the structuring process. The topography of the LINF was investigated by scanning electron microscopy and laser scanning microscopy. The electrochemical surface area of the electrodes was determined by cyclic voltammetry based on the charging of the double-layer. The total capacity of the nickel LINF electrodes was measured by galvanostatic charge-discharge to test their capability for supercapacitor applications. The surface area enlargement and therefore the total capacity increases with decreasing line distance. The LINF structure provides a surface area enlargement up to a factor of 1600 and a total capacity up to 2 C cm-2.