A hydrogen-bond network sieve enables selective OH−/Cl− discrimination for stable seawater splitting at 2.0 A cm−2

Abstract

Direct seawater electrolysis offers a sustainable route to producing green hydrogen, but it suffers from severe chloride corrosion at conventional anodes. Challenging the long-standing electrostatic repulsion model for chloride suppression, we reveal that interfacial hydrogen-bond networks govern selective OH⁻ transport while excluding Cl⁻. Through integrated ab initio molecular dynamics and in situ Raman spectroscopy, we demonstrate that structured water layers near the anode form a dynamic H-bond sieve: OH⁻ undergoes barrier-free transfer by reconfiguring the H-bond network, while Cl⁻ faces high rejection due to its inability to reorganize interfacial water. Leveraging this mechanism, we engineer an interfacial H-bond buffer using SO₄²⁻ and CO₃²⁻ anions. SO₄²⁻ reinforces the H-bond network to block Cl⁻, while CO₃²⁻ acts as an OH⁻ pump to mitigate depletion at high current densities. The optimized buffer enables a CoFe LDH anode to achieve exceptional activity (overpotential of 291.4 mV at 300 mA cm⁻²) and stability (550 h at 2.0 A cm⁻²). When integrated into an anion-exchange membrane electrolyzer, the system delivers industrially relevant performance (2.51 V at 1.0 A cm⁻², 4.85 kWh Nm⁻³ H₂) with 1000 h stability. This work establishes a transformative H-bond-mediated ion-sieving paradigm for corrosion-resistant seawater electrochemistry.