Quantification of the effect of ultrasound in a PEM water electrolyser with operando neutron imaging and numerical simulations.

Abstract

This study investigates the effect of ultrasound (US) on the electrochemical performance and two-phase flow regimes within a custom-designed polymer electrolyte membrane water electrolyser (PEMWE) cell. The electrolyser cell was equipped with a US transducer-receiver pair that allowed US propagation through the active area. Operando neutron imaging experiments were conducted at the Institut Laue-Langevin (ILL), utilizing both in-plane and through-plane radiography to quantify water thickness as a proxy for gas distributions across different electrolyser components under varying operating conditions. Simultaneously, real-time monitoring of electrochemical performance was carried out, with the goal of identifying the effect of two-phase mass transport conditions on PEMWE losses. The results reveal a non-monotonic dependence of the US effect on current density and the flow regime that emerges in the flow channels. At intermediate current densities (∼1000 mA cm-2), US induces a measurable reduction in cell voltage, correlated with increased water occupancy in the flow channels, consistent with enhanced gas removal. In contrast, at high current densities (∼6000 mA cm-2), US leads to reduced water content in the channels and a deterioration in cell performance, suggesting a transition in the governing two-phase flow regime. Computational fluid dynamics simulations of the baseline flow field support the experimental observations by identifying the presence of slug flow under these conditions.

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