Voltage losses in zero-gap alkaline water electrolysis

Reducing the gap between electrodes and diaphragm to zero is an often adopted strategy reduce ohmic drop in alkaline water electrolyzers for hydrogen production. We provide a thorough account of current–voltage relationship such zero-gap configuration over wide range electrolyte concentrations current densities. Included are voltage components that not experimentally quantified like those due bubbles, hydroxide depletion, dissolved oxygen. As commonly found configurations, resistance was substantially larger than separator. find this because relatively flat electrode area facing active, likely separator pore blockage by gas, itself, or solid deposits. Over e-folding time-scale ten seconds, additional arise, gas bubbles holes. For below 0.5 M, overpotential observed, associated with local depletion at anode. Finally, high supersaturation oxygen significantly increase equilibrium potential elevated Most these losses shown be easily avoidable introducing small 0.2 mm gap, greatly improving performance compared zero-gap.