SNU researchers develop technology for simultaneous production of purified water and hydrogen — proposing a sustainable water treatment platform with integrated energy recovery

Seoul National University College of Engineering announced that a research team led by Professor Sung Jae Kim from the Department of Electrical and Computer Engineering has developed a new energy-harvesting water purification system capable of producing both purified water and hydrogen simultaneously.

This innovative technology removes impurities from saline water while reducing hydrogen ions at the electrode to generate hydrogen gas. The system integrates desalination and water electrolysis into a single process, thereby minimizing energy loss compared to conventional water-purification systems.

Designed as a compact and modular unit, the system allows for flexible scalability through the assembly of multiple modules. This makes the technology highly promising for resource-limited environments, such as spacecraft, disaster areas, and remote military sites where clean water and energy supplies are strictly limited.

Supported by the Korea Ministry of Science and ICT (MSIT) and the SNU Energy Initiative (SNUEI), the study has been published online in Communications Materials (Nature Portfolio, 2025), a leading journal in the field of materials science.

Securing both clean water and clean energy is one of the most urgent global challenges. However, this problem is paradoxical: water purification requires electricity, while electricity production often requires water. As a result, there is a critical need for technologies that can address both challenges at once.

To address this issue, Professor Kim’s research team developed a combined freshwater–hydrogen production platform based on ion concentration polarization (ICP)*, a nanoelectrokinetic phenomenon that enables salt removal and hydrogen generation within a single module using a cation exchange membrane.

* Ion concentration polarization: When an electric field is applied across an ion-selective membrane, ions separate into enriched and depleted zones on opposite sides of the membrane.

By integrating desalination and water electrolysis processes, the new system provides purified water while simultaneously producing hydrogen energy. The core mechanism operates as follows:

When electrical current is applied across a cation exchange membrane (CEM), salt and other contaminants are removed on one side of the membrane, producing purified water. While on the other side, hydrogen ions (H⁺) receive electrons at the electrode and are reduced to hydrogen gas (H₂). In other words, a single electrochemical process produces purified water and hydrogen at the same time (see Figure 1).

To experimentally validate this principle, the team first fabricated a microfluidic device, enabling simultaneous visualization of hydrogen bubble generation and purified-water regions (ion-depleted zones) via fluorescence imaging. They then built a finger-sized meso-scale device using 3D printing, successfully achieving stable purified-water production and hydrogen generation at several milliliters per hour (see Figure 2).

* Meso-scale: Size range between microscopic structures and macroscopic components, typically hundreds of micrometers to several centimeters.

The system recovered approximately 10% of the electrical energy used for purification in the form of hydrogen energy. Hydrogen production increased linearly with increasing current, confirming the feasibility of scaling. Moreover, the device consistently produced purified water even from high-salinity brines, demonstrating its potential for seawater and highly saline water applications.

Unlike existing technologies such as electrodialysis (which requires complex alternating ion-exchange membrane stacks) and reverse osmosis* (which requires high-pressure pumping), the proposed system operates using a single membrane structure and functions without high pressure pumps. This simplicity and lightweight form factor make the device ideal for portable or distributed water purification systems.

* Reverse osmosis: A water purification technology that uses a semipermeable membrane and high pressure to allow water molecules to pass through while blocking salts and contaminants. It is commonly used for seawater desalination and the production of high-purity water.

Professor Kim’s team has demonstrated a technology to recover a portion of the electrical energy used in water purification in the form of hydrogen gas—recovering approximately 8–10% of energy that would otherwise be lost in conventional ICP desalination. If the produced hydrogen is supplied to a fuel cell, the system could evolve into a self-powered, energy-autonomous water purification platform, capable of generating a part of its own operating electricity.

Because the device is designed as a modular, scalable platform, capacity can be increased by connecting multiple units in parallel—similar to assembling LEGO blocks. This adaptability enables applications ranging from small personal purifiers to mobile purification units for disaster response, as well as operations in military or space environments.

Notably, this ICP-based system is capable of removing not only salt but also heavy metals, fine particulates, and bio contaminants, suggesting wide applicability in practical fields such as environmental remediation, water treatment, biomedical devices like artificial kidneys.

Professor Sung Jae Kim, corresponding author of the study, stated, “The key significance of this research is that it demonstrates a system capable of addressing water and energy challenges simultaneously, rather than handling them separately. We plan to further expand the modular design for large-scale implementation so that anyone—whether in disaster zones or spacecraft—can easily secure both water and energy even in extreme environments.”

Co-corresponding author Dr. Sungjae Ha (ProvaLabs, Inc.) added, “This is one of the first demonstrations of nanoelectrokinetic technology for concurrent hydrogen production and desalination, establishing a foundation for water–energy self-sufficiency.”

First author Dr. Jihee Park (SNU Energy Initiative) noted, “A major discovery of this research is that ion transport occurring during purification can be harnessed to recover energy at the same time. This work presents the possibility of small-scale purifiers that partially power themselves—marking a starting point for next-generation sustainable technologies addressing both environmental issues and energy shortages.”

Co–first author Dr. Sehyuk Yoon (SNU Soft Foundry Institute) added, “This study demonstrates that ICP-based microfluidic technologies can be expanded to meso-scale devices with verified operational performance. The integration of desalination and hydrogen production within a single module shows strong potential for future field-deployable water and energy systems.”

Dr. Jihee Park and Dr. Sehyuk Yoon continue to work in the SNU Energy, Environment and Sustainability Laboratory, developing methods to further enhance system efficiency. They also plan to pursue research on battery metal dendrite suppression and energy resource recovery in future energy applications.

* Dendrite: Tree-like needle-shaped crystals that can form in battery electrodes.

□ Introduction to the SNU College of Engineering

Seoul National University (SNU) founded in 1946 is the first national university in South Korea. The College of Engineering at SNU has worked tirelessly to achieve its goal of ‘fostering leaders for global industry and society.’ In 12 departments, 323 internationally recognized full-time professors lead the development of cutting-edge technology in South Korea and serving as a driving force for international development.