Seawater electrolysis at ultra-high current density: A comparative analysis of cylindrical versus conical electrodes

Seawater electrolysis preferentially leans towards Chlorine Evolution Reaction (CER) over Oxygen Evolution Reactions (OER) under conventional conditions, but OER becomes more dominant at sufficiently higher current densities. In this study, we evaluated the effector of cylindrical and conical electrode geometries on CER and hydrogen production at high current density (i.e., >1 A cm −2 ). We found the point of lowest CER within a voltage range of 40 V–90 V. Conical electrodes, optimized to reduce CER, produced a magnitude less chloride (502 ppb) than cylindrical electrodes (1485 ppb) at nearly double the current density (∼12 and ∼6 A cm −2 respectively). However, this reduction in CER with conical electrodes was accompanied by a 25% decrease in hydrogen production. In addition, both cylindrical and conical electrodes were able to heat 500 ml of seawater by approximately 6–7 °C over a 2-min period with cylindrical electrodes heating slightly less than conical electrodes. • Comparison between cylindrical and conical graphite electrodes. • Conical electrodes suppress CER by 66% compared to cylindrical electrodes. • Cylindrical electrodes produce 25% more hydrogen at CER minima over conical. • Finite-element modeling reveals electrical potential 50x higher than conventional.