Rethinking alkaline water electrolysis under industrial conditions

Alkaline water electrolysis supplies most installed water-electrolyser capacity, yet the technology and its perceived limits have not fundamentally changed in a century. Rather than inherent chemistry, we argue that these limits are the consequence of traditional operating conditions at near-atmospheric pressure, low current density, and steady state. The performance gap with proton exchange membrane systems persists across a coupled hierarchy of losses: kinetic and ohmic losses at the electrodes and separator in concentrated KOH; shunt and reverse currents along the manifolds of bipolar stacks; and power-conversion, compression and thermal-management losses at the plant level. In this Review, we outline how closing this gap calls for coordinated advances in electrode and separator materials, stack architecture, power electronics and plant-level integration, evaluated under realistic industrial conditions of concentrated alkali, elevated temperature and pressure, and dynamic loads. By pursuing these advances, we can rebuild alkaline electrolysis from first principles into a flexible workhorse for low-carbon hydrogen production.