Energy-efficient modular water purification system via concurrent freshwater and hydrogen generation using ion concentration polarization

This study demonstrates a compact, modular platform that simultaneously generates freshwater and hydrogen gas by leveraging nanoelectrokinetic ion concentration polarization through cation-exchange membranes (CEMs). Using a microfluidic platform, we demonstrate real-time concurrent hydrogen production at the cathode and freshwater production adjacent to the anodic side of CEM. Ion removal is confirmed by fluorescence imaging and ion chromatography, while gas generation is validated using pH indicators. To evaluate practical performance, the device is scaled-up to a mesoscale platform, enabling quantitative measurement of purification efficiency and hydrogen output across varying parameters such as applied currents and source water concentration, etc. We demonstrate that approximately 10% of input electrical energy is recovered as hydrogen, improving overall energy efficiency and enabling the possibility of periodically substituting externally supplied power with internally produced hydrogen. At higher applied currents, hydrogen ions transport through CEM is favored over sodium ion transport, boosting hydrogen production efficiency and device durability. This energy-recoverable purification platform reduces infrastructure needs and suits for decentralized and portable applications in resource-limited settings. This study demonstrates a compact, modular platform that simultaneously generates freshwater and hydrogen gas by leveraging nanoelectrokinetic ion concentration polarization through cation-exchange membranes.