Hybrid Alkali-Salt-Acid Electrochemical Device for Electricity-Efficient Desalination and H₂Generation

Integrating bifunctional applications in a single electrochemical device is highly desirable as it potentially enhances the electrical efficiency. We herein report a hybrid alkali-salt-acid electrochemical cell (h-ASAEC) that is capable of simultaneously implementing electrodesalination and H2 generation in an electricity-efficient manner by lowering the electrical energy input required for electrodesalination and H2 generation, thanks to the electrical driving force of neutralization energy by virtue of the pH gradients in the three-compartment cell. The h-ASAEC at an electrolytic current density of 40 mA/cm2 performs electrodesalination with minimal parasitic chemistry while generating ∼33 mL/h of H2 at a terminal voltage of ∼1 V, which is only half of the voltage required in a symmetric configuration. Contrary to the conventional desalination process, the low-voltage electrodesalination in the h-ASAEC noticeably improves the electrical energy efficiency and prevents competitive parasitic chemistry.