Bubble dynamics on laser structured porous nickel electrodes

Hydrogen produced by water electrolysis using renewable energy sources is a promising approach towards a net-zero-emission-industry that is replacing fossil fuels [1]. One cost effective and mature technology for hydrogen production is alkaline water electrolysis. The advantage is the usage of non-critical electrode materials like nickel instead of noble metals such as platinum needed for acidic water electrolysis [2]. However, compared to other technologies alkaline water electrolysis shows larger partial load limits, lower current densities and lower operating pressures [3]. Nevertheless, by enhancing the bubble growth and detachment from the electrode, the overall efficiency of alkaline electrolysis can be improved [4] to make it even more competitive for future large scale installations.

By influencing the detachment behavior of the bubbles, the efficiency can be increased. Laser technology depicts a promising approach to create a supportive micro- and nano-texturing of the electrodes. Specifically, the Direct Laser Interference Pattering (DLIP) technique is applied for structuring the electrode surfaces to increase their wettability [5]. By two overlapping laser beams, a periodic line-like pattern with a spatial period of 6.0 μm is generated.

The present study uses a 3D printed electrolysis cell developed for the analysis of the bubble dynamics and the electrochemical performance of structured and non-structured electrodes. Therefore, a removable working electrode holder is applied to a cell with optical access from the side and the top of the working electrode. Two different observation perspectives allow to study the bubble growth, the detachment size and the electrode coverage at the same time. By characterizing the electrodes beforehand using cyclic voltammetry (CV) to determine the double-layer capacitance and thus the electrochemical active surface area, a profound characterization of different laser structured electrodes is given.

References:

[1] L. Lüke, Chem. Ing. Tech. 2020, 92, No. 1–2, 70–73.
[2] S. Wang, Nano Converg. 2021, 8, 4.
[3] M. Carmo, Int. J. Hydrog. Energy. 2003, 38, 4901-4934.
[4] R. Iwata, Joule. 2021, 5, 1-14.
[5] R. Baumann, J. Laser Micro Nanoeng. 2020, 15, 2.