Deactivation Mechanisms and timescales of nickel electrodes in alkaline water electrolysis
L.L.M. Vijverberg (TU Delft - Applied Sciences)
J.W. Haverkort – Mentor (TU Delft - Energy Technology)
DA Vermaas – Graduation committee member (TU Delft - ChemE/Transport Phenomena)
Ruud Kortlever – Graduation committee member (TU Delft - Large Scale Energy Storage)
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Abstract
Alkaline water electrolysis emerges as a promising technology for green hydrogen production, playing a significant role in global decarbonization. Nickel-based electrodes are widely used in alkaline water electrolysis due to their excellent catalytic properties for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). However, nickel electrodes often experience a decrease in activity over time. Attempts of existing literature to investigate nickel deactivation employ conditions that differ from industry standards. Therefore, a more profound understanding of these phenomena under industry-relevant conditions is crucial for averting specific degradation pathways in future electrode design. This thesis investigates the deactivation phenomena and the timescales of untreated nickel electrodes during the OER and HER at 323 K and 30 wt% KOH, employing a current density of 1 A cm-2. The electrolyte concentration and current density match industry standards, and the temperature aligns more with industrial practices than literature. The OER overpotential increases under these conditions in 2.5 hours by 0.19 V and still increases after this period. The HER overpotential increases by 0.65 V and stabilizes after 20 minutes. Electrochemical and surface analytical tests suggest that both reactions primarily deactivate due to a redox reaction.