Investigation of Nickel-Based Gas Diffusion Electrodes for Implementation in a Hybrid Alkaline Water Electrolysis Cell
Authors: Sanderbrandes Lars , Turek Thomas 
Published: December 2024

Substantial amounts of green hydrogen will be required for the transformation of several industry sectors toward a more sustainable operation. The future chemical industry, in particular, will be in high demand since the environmental impact of processes like ammonia and methanol synthesis can be significantly reduced via the use of green hydrogen. Moreover, hydrogen is one possible option for storing surplus electrical energy, the production of which is unavoidable when switching to renewable sources of electricity [1].

Among the different available technologies, Alkaline Water Electrolysis (AEL) is the most cost-effective and developed variant [2]. However, conventional AEL encounters challenges such as a significant gas cross-contamination, especially in the part-load range [3]. A novel hybrid cell arrangement proposed by Koj et al. [3] (Fig. 1 (a)) aims for mitigation of these cross-contaminations by implementing gas diffusion electrodes (GDEs). As an additional benefit, only one instead of two electrolyte cycles is needed. This simplifies the electrolysis system noticeably.

In this work, the development and employment of GDEs for the oxygen evolution reaction (OER) in the hybrid cell arrangement will be investigated. The developed electrodes are based on prior research of Kaiser et al. [4]. The GDEs are manufactured by spray-coating nickel mesh with a mixture of catalyst components dispersed in water. The catalyst is mainly composed of nickel particles, with low amounts of iron as a secondary catalyst to enhance the electrode performance [4]. PTFE acts as the binder, while methyl cellulose is used as a pore-building agent. A sintering step creates the necessary porous structure by removing the methyl cellulose and melting the PTFE. A typical GDE structure of hydrophilic and hydrophobic pores is created in the process.

This study investigates the impact of each catalyst component and additional variables such as the catalyst load on the electrode performance. The main point of consideration is the mass fraction of each component, which is varied systematically. Multiple electrochemical (linear sweep voltammetry, electrochemical impedance spectroscopy, chronopotentiometry, cyclic voltammetry) and physicochemical measurements (BET surface area, porosity, pore size distribution, bubble point) are conducted. Fig. 1 (b, c) illustrates the effect of methyl cellulose content and catalyst loading and their subsequent effect on the electrode performance, as shown exemplary with linear sweep voltammetry measurements. The GDEs appear to benefit from a higher methylcellulose content and a higher catalyst load. The collected data can be used to determine an optimal catalyst composition. Furthermore, the connections between physical structure, catalyst composition and electrode performance are to be unraveled. Subsequent research will focus on evaluating electrodes with optimal parameters in a full-cell setup, specifically addressing cell voltage, stability and the overall goal of reducing the gas cross-contamination.

Literature:

[1] M. Yue, H. Lambert, E. Pahon, R. Roche, S. Jemei, D. Hissel, Renewable and Sustainable Energy Reviews 146, 2021.

[2] A. Buttler, H. Spliethoff, Renewable and Sustainable Energy Reviews 82(3) 2018.

[3] M. Koj, J. Qian, T. Turek, International Journal of Hydrogen Energy 44(57) 2019.

[4] M. Kaiser, F. Gäde, J. Brauns, T. Turek, Catalysts 13(9) 2023.

Figure 1