Nano/Microstructuring of Nickel Electrodes by Combining Direct Laser Interference Patterning and Polygon Scanner Processing for Efficient Hydrogen Production

The present work utilizes direct laser interference patterning in conjunction with a polygon scanner system to fabricate micro- and nanostructures on the surface of nickel foils. A picosecond pulsed laser source with an average power of ≈470 W is used to pattern line-like structures having spatial periods of 11.0 and 25.0 μm and a maximum structure depth of up to 15 μm. The scanning speed and the number of consecutive scans, ranging from 5 to 500, are varied in order to assess their influence on the structure formation process. Furthermore, the use of ultrashort pulses permits the production of hierarchical surface structures having up to four feature size levels because of incubation effects and growth of different types of laser-induced periodic surface structures. 2D-fast Fourier transforms are applied to scanning electron microscopy images for analyzing the evolution of features from the nano- to microscale. The method proposed here permits the reduction of 22% in the overpotential of the hydrogen evolution reaction, which linearly correlates to the drop in energy required to drive this chemical reaction.