Carbon corrosion: A novel termination mechanism of the water electrolysis plateau during voltage reversal

Abstract Although the mechanism of the voltage reversal process due to overall hydrogen deficiency is clear, the termination mechanism of the water electrolysis plateau (WEP) is still very controversial. In this work, for the first time, the termination mechanism of the WEP is analyzed by synchronously detecting the internal resistance (IR) change in the process of the voltage reversal. The results show that in the WEP, the IR of the cell increases slowly, but increases sharply once the plateau is finished. The IR-corrected voltages have directly indicated that the termination of the WEP is mainly due to a significant increase in cell IR resulting from carbon corrosion, rather than commonly believed OER (oxygen evolution reaction) catalyst deactivation and lack of water inside the cell. Remarkably, the IR at the end of the WEP is about 180 mΩ cm2, which is independent of anode gas relative humidity, IrO2 loading, and carbon support type. Besides, the performance of the cell damaged by voltage reversal is partly recoverable, which may be due to the rehydration of the proton exchange membrane and the reestablishment of the charge and gas transport channel during the reactivation process.