Decoupled Water Splitting for Green Hydrogen Production: Reshaping Water Electrolysis

Green hydrogen production at scale is essential to fight global warming and climate change. The present water electrolysis technologies present significant barriers to meet this challenge, due to high system and operational costs that emerge from the need to divide each cell into gas-tight cathodic and anodic compartments to avoid mixing hydrogen with oxygen, and from intrinsic energy losses in the complex oxygen evolution reaction. Recent efforts to overcome these barriers include transformative approaches to decouple the hydrogen and oxygen evolution reactions using soluble redox couples or solid redox electrodes that mediate the ion exchange between the primary electrodes such that hydrogen and oxygen are generated at different times and/or different cells. This leads the way to membraneless electrolyzer architectures that can enhance safety, reduce system costs, and provide operational advantages such as high-pressure hydrogen production. In particular, E-TAC water slitting offers these advantages as well as ultrahigh efficiency and compact design of rolled electrode assemblies, opening new frontiers for advanced water electrolysis. (authors)