Sinusoidal waveform modulated voltage supply for current improvement of water electrolyzers based on multi-physical dynamics

In this paper, the effect of the sinusoidal waveform modulated voltage (SWMV) on the performance of the water electrolyzers is investigated based on multi-physical dynamics. By introducing the dynamic bubble in the industrial water electrolyzers, Sinusoidal waveform modulated voltage supply can theoretically improve the overall current density by taking advantage of the time-scale differences between the electrochemical reaction and the diphasic flow. In order to prove the analysis, a three-dimensional dynamic multiphysics model of the alkaline electrolyzer is established by considering the bidirectional coupling of the diphasic flow field and the current density field, which are then validated by the experiment on the RTLab-based electrolysis testbed. Results show that the overall hydrogen production rate can be improved by 1.82 % to 3.07 % under sinusoidal waveform modulated voltage with the frequency ranging from 0.01 Hz to 9 Hz, which is primarily attributed to the transient process of the diphasic flow in seconds. Furthermore, the time constant of the flow field has proved to be a critical parameter determining the current gain brought by sinusoidal waveform modulated voltage, where up to 4.5 % promotion of the current density is realized by extending the flow channel. The discovery is expected to pave the way for renewable power-to‑hydrogen by bridging the gap between fluctuating renewable energy and water electrolyzers.