In operando synchrotron X-ray radiography studies of polymer electrolyte membrane water electrolyzers

• Synchrotron X-ray radiography was applied to polymer electrolyte membrane water electrolyzers.
• Gas transport in the porous transport layer occurs through selective pathways.
• The number of pathways for the gas transport is a function of current density.

Polymer electrolyte membrane water electrolysis (PEL) cells are studied in-operando by synchrotron X-ray radiography. Two-phase flow phenomena associated with the evolution of oxygen and hydrogen in the surrounding water are investigated on a running electrolyzer cell. We examine the gas bubble discharge from the porous transport layer (PTL) into the flow channel and discuss the transport of bubbles in the flow channel. The transport of gas inside the PTL and the number of gas bubble discharge sites is examined and correlated with current density.