Hydrogen production with seawater-resilient bipolar membrane electrolyzers

Generation of H2 and O2 from untreated water sources represents a promising alternative to ultrapure water required in contemporary pro-ton exchange membrane-based electrolysis. Bipolar membrane-based devices, often used in electrodialysis and CO2 electrolysis, facilitate impure water electrolysis via the simultaneous mediation of ion trans-port and enforcement of advantageous microenvironments. Herein, we report their application in direct seawater electrolysis; we show that upon introduction of ionic species such as Na+ and Cl- from seawater, bipolar membrane electrolyzers limit the oxidation of Cl- to corrosive OCl- at the anode to a Faradaic efficiency (FE) of 0.005%, while proton exchange membrane electrolyzers under compa-rable operating conditions exhibit up to 10% FE to Cl- oxidation. The effective mitigation of Cl- oxidation by bipolar membrane electrolyz-ers underpins their ability to enable longer-term seawater electrolysis than proton exchange membrane assemblies by a factor of 140, sug-gesting a path to durable seawater electrolysis.

Automated summary

Generation of H2 and O2 from untreated water sources is a promising alternative to ultrapure water required in contemporary proton exchange membrane-based electrolysis. Bipolar membrane-based devices, commonly used in electrodialysis and CO2 electrolysis, can enable impure water electrolysis by mediating ion transport and creating favorable microenvironments. This study demonstrates the application of bipolar membrane electrolyzers in direct seawater electrolysis, which effectively mitigates the oxidation of Cl- and enables longer-term seawater electrolysis compared to proton exchange membrane assemblies.