Bubble dynamic behaviors in the anode porous transport layer of proton exchange membrane electrolyzers using a microfluidic reactor

Gas bubbles in proton exchange membrane (PEM) electrolyzers are the main source of mass transport loss in the porous transport layer at high current densities. However, the complexity and opacity of the porous transport layer make it challenging. In this study, a microfluidic reactor with an electrochemical reaction boundary is designed to observe the bubble behaviors in the porous transport layer. The detailed bubble growth and detachment mechanisms are explored based on the visualization results. Results show that the gas phase evolution undergoes the unsteady growth stage and the steady stage. Bubble behaviors including free movement, coalescence, breakthrough and detachment are observed for a single bubble in the porous transport layer. The gas phase saturation in the porous transport layer as well as the applied voltage increases with increasing the current density. Moreover, as the flow rate increases, the time for the first bubble detachment and the number of bubble detachment gradually decrease, and the average detachment radius of the bubble gradually increases. A lower applied voltage is needed under a higher flow rate due to low mass transfer resistance. The proposed method can help us understand the dynamic behavior of bubbles in the porous transport layer of PEM electrolyzers.