Impact of AC/DC converter ripples and inductance on the performance and lifetime of alkaline water electrolyzers: Experimental investigation

Power electronics represent a significant fraction of the capital cost of water electrolysis systems; however, the electrochemical influence of converter-side ripples on alkaline water electrolyzers (AWEs) remains insufficiently understood. This study experimentally investigated the effects of voltage ripple features and reactor inductance on the electrochemical response, hydrogen generation, bubble dynamics, and oxygen evolution reaction (OER) catalyst durability of a 4-cell AWE operated under experimentally imposed ripple conditions mimicking those of an IGBT-based AC/DC converter. Square-wave voltage signals with maximum and minimum values of 8.8 V and 0.0–5.6 V were applied over a frequency range of 100–4000 Hz using series reactors with inductances of 0.083, 0.33, and 3.3 mH. Although larger reactors effectively suppressed ripple amplitudes, comparable ripple reduction was achieved through high-frequency operation, enabling smaller reactors with lower Ohmic losses, reduced footprint, and potentially lower system cost. High-speed visualization revealed no measurable influence of ripple characteristics on hydrogen bubble dynamics. Similarly, hydrogen production rates and current efficiencies were governed primarily by the DC component of the current. Durability tests of NiCoOx/Ni OER catalysts further indicated negligible ripple-induced degradation. These findings provide practical guidance for optimizing converter design and reactor sizing in large-scale green hydrogen production systems.