Femtosecond-laser structuring of Ni electrodes for highly active hydrogen evolution

• Published in: Electrochimica acta Vol. 247; pp. 1130 - 1139
• Main Authors: Rauscher, Thomas, Müller, Christian Immanuel, Gabler, Andreas, Gimpel, Thomas, Köhring, Michael, Kieback, Bernd, Schade, Wolfgang, Röntzsch, Lars
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.09.2017; Elsevier BV
• Subjects: alkaline electrolysis; Conical bodies; Electrode materials; Electrodes; Electrolysis; Electron microscopy; Feasibility; femtosecond laser pulse process; Femtosecond pulses; Fluence; Hydrogen; hydrogen evolution; Hydrogen evolution reactions; Hydrogen production; Lasers; Morphology; Process parameters; Roughness; roughness factor; Scanning electron microscopy; structured electrodes; Studies; Surface area; structured electrodes; roughness factor; hydrogen evolution; alkaline electrolysis; femtosecond laser pulse process
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2017.07.074

[Display omitted] •Tailoring the surface morphology of Ni electrodes by femtosecond laser pulse processing.•Generation of high and adjustable surface areas.•Enhanced specific hydrogen production as a result of surface structuring.•No major changes of the intrinsic HER-activity due to fs laser pulse processing. Hydrogen production by alkaline water electrolysis has attracted great attention due to the feasibility of large scale H2 production and the use of non-precious electrode materials. In particular, efficient electrodes towards the hydrogen evolution reaction (HER) consist of porous or skeletal Ni-based catalysts. In this contribution, a unique surface processing technique using a femtosecond (fs) laser pulse process was utilized to enlarge the surface area of Ni aiming to enhance significantly the HER-activity. Fs laser structured Ni surfaces were processed using different laser process parameters (e.g. fluence, spot size and scan line overlap). Surface morphology was studied by scanning electron microscopy. Under the chosen process conditions arrays of conical surface structures were obtained, which are significantly covered by redeposited particles using a fluence far above the ablation threshold. Electrochemical investigations (CV, EIS, steady-state polarization curves) conducted in 29.9wt.-% KOH at 333K (industrial conditions) point out that the fs laser structured electrodes reveal a high and adjustable surface area with a roughness factor between 6 and 73. The roughness of the fs laser structured surfaces has a significant impact on the HER leading to a reduced overpotential (η300=280mV, reduction by approximately 45% compared to smooth Ni). In fact, the results clearly show the feasibility of the fs laser pulse technique for processing highly structured electrodes without affecting the intrinsic HER-activity significantly.