Current status of membraneless water electrolysis cells

Abstract Commercial water electrolysis cells require a resistive, ion-permeable, gas-impermeable separator membrane between the electrodes to stop the hydrogen bubbles from mixing with the oxygen bubbles, and vice versa. This work reviews the current status of ‘membraneless’ water electrolysis cells that avoid need for such a separator membrane. Three different approaches have been employed to realize such cells. In the first, laminar flow within a microfluidic reaction chamber has been used to entrain the hydrogen and oxygen gas bubbles in separate, parallel streams that do not mix. In the second approach, closely-spaced porous electrodes have had liquid electrolyte divergently pumped through them to sweep the produced hydrogen and oxygen bubbles to different locations. In the most recent, promising approach, gas diffusion electrodes have been used to directly extract gas as it is produced, thereby avoiding discernable bubble formation and eliminating the need for a separator membrane to keep the gases separate.