Quantitative study on gas evolution effects under large current density in zero-gap alkaline water electrolyzers

The gas evolution effects on the electrolytic voltage under large current density in zero-gap alkaline water electrolyzer are investigated with specifically designed segmented electrodes and electrochemical measurements. 4 possible influencing pathways from gas evolution to electrolysis performance are summarized and quantified respectively for the first time. It is found that the impact of gas evolution behaviors on electrolytic voltage at up to 0.5 A/cm2 is below 50 mV, or 4% of total overpotential. Electrolysis voltage is split up to demonstrate the contribution of gas evolution induced impedance in ohmic and activate overpotentials.