Simultaneous Desalination and Hydrogen Production by Nanoelectrokinetic Selective Ion Separation

To address ‘Water-Energy Nexus’ challenges, we aim to develop a novel system enabling simultaneous desalination and hydrogen production by precisely regulating nanoelectrokinetic ion transport through ion exchange membranes within a micro-nanofluidic platform. Applying voltage to a cation exchange membrane, which permits the passage of only cations, leads to the creation of an ion depletion zone (IDZ) on the anodic side and an ion enrichment zone (IEZ) on the cathodic side of the membrane, known as Ion Concentration Polarization (ICP) phenomenon. Our key strategy is to produce desalted water from the IDZ and simultaneously produce hydrogen at the reduction electrode. Using microfluidic channels connected with a cation exchange membrane and microelectrodes, we visualize the generation of acidic brine suitable for hydrogen production at the IEZ (i.e. gas bubbles at the reduction electrode), during desalination at the IDZ. Furthermore, we analyze and control the transport of Na⁺ and H⁺ ions competing through the membrane within highly branched microchannels under various operating conditions. This nanoelectrokinetic study for the ion transport through the ion exchange membrane will play a key role in realizing simultaneous water desalination and electrolytic hydrogen production.