Abstract
Overshoot voltage phenomenon often occurs when the proton exchange membrane (PEM) electrolyzer is in the intermittent operation, which makes H2 production energy consumption increase significantly and its lifetime reduce rapidly, especially to the high-power electrolyzers in the industrial applications. Up to now, the phenomenon has been rarely understood and its process is elusive. Therefore, in this work, firstly, we find that the polarization curve of PEM electrolyzers happening S distortion synchronize with the appearance of overshoot voltage phenomenon. Secondly, through in-situ Raman characterization, we find that involvement and disappearance of H2O in the hydrogen evolution reaction (HER) is the key factor causing and resolving this phenomenon. Finally, we used EPMA to exclude metal cations affection. Also, by micro-CT, EIS test, visualization PEM electrolyzer inside model and COMSOL electromagnetic simulation, we find that anode catalyst layer porosity reduction directly affects water absorption of membrane as well as current variation leads to eddy currents generation which is deepen unequal current distribution. These are two important reasons for the involvement of H2O in HER. In summary, these findings elucidate the mechanism of overshoot voltage phenomenon for the first time, which contributes to design novel electrical protection schemes and advanced membrane electrodes for PEM electrolyzers, thus they can help to achieve cost reduction and efficiency improvement in the green hydrogen industry.
Published Version
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