A Dual‐Cation Exchange Membrane Electrolyzer for Continuous H2 Production from Seawater

Abstract

Abstract Direct seawater splitting (DSS) offers an aspirational route toward green hydrogen (H2) production but remains challenging when operating in a practically continuous manner, mainly due to the difficulty in establishing the water supply–consumption balance under the interference from impurity ions. A DSS system is reported for continuous ampere‐level H2 production by coupling a dual‐cation exchange membrane (CEM) three‐compartment architecture with a circulatory electrolyte design. Monovalent‐selective CEMs decouple the transmembrane water migration from interferences of Mg2+, Ca2+, and Cl− ions while maintaining ionic neutrality during electrolysis; the self‐loop concentrated alkaline electrolyte ensures the constant gradient of water chemical potential, allowing a specific water supply–consumption balance relationship in a seawater–electrolyte–H2 sequence to be built among an expanded current range. Even paired with commercialized Ni foams, this electrolyzer (model size: 2 × 2 cm2) continuously produces H2 from flowing seawater with a rate of 7.5 mL min−1 at an industrially relevant current of 1.0 A over 100 h. More importantly, the energy consumption can be further reduced by coupling more efficient NiMo/NiFe foams (≈6.2 kWh Nm−3 H2 at 1.0 A), demonstrating the potential to further optimize the continuous DSS electrolyzer for practical applications.

Keywords

• electrocatalysis
• green hydrogen production
• seawater splitting
• water migration balance