The global push for sustainable energy sources has placed green hydrogen at the forefront, yet its widespread adoption faces a critical hurdle: the reliance on vast quantities of freshwater for electrolysis. With freshwater resources under increasing strain, the prospect of directly producing hydrogen from the planet’s most abundant resource—seawater—offers a transformative solution. A significant breakthrough from the Korea Institute of Energy Research (KIER) marks a pivotal step forward, as researchers have developed a durable carbon cloth-based electrode capable of stably producing hydrogen from seawater for over 800 hours under industrial-scale conditions.
The Imperative of Green Hydrogen and the Freshwater Dilemma
Hydrogen is increasingly recognized as a cornerstone for decarbonizing heavy industries, from steelmaking to power generation. The cleanest form, “green hydrogen,” is produced by splitting water into hydrogen and oxygen through electrolysis, powered by renewable electricity. However, conventional electrolysis systems predominantly rely on highly purified freshwater, a resource that is unevenly distributed and becoming scarcer due to climate change, population growth, and competing demands from agriculture and industry.
The ocean, covering approximately 71% of the Earth’s surface, presents a nearly inexhaustible supply of water for hydrogen production. Utilizing seawater directly would alleviate pressure on freshwater reserves and enable hydrogen production in coastal and island nations with limited access to clean water.
Seawater’s Challenges in Hydrogen Production
Despite its abundance, seawater poses significant challenges for electrolysis. Its complex composition, rich in dissolved salts, organic matter, and various ions like chloride (Cl⁻), magnesium (Mg²⁺), and calcium (Ca²⁺), leads to several detrimental effects:
- Corrosion: Chloride ions are highly corrosive to electrode materials, rapidly degrading their performance and lifespan.
- Precipitation (Scaling): Magnesium and calcium ions can form insoluble precipitates (scaling) on electrode surfaces, blocking active sites and reducing electrolysis efficiency.
- Competing Reactions: The presence of chloride ions promotes the chlorine evolution reaction (CER) at the anode, which competes with the desired oxygen evolution reaction (OER). This not only contaminates the produced hydrogen but also generates toxic chlorine gas and corrodes the electrode.
- Energy Consumption: Desalination, often a prerequisite for using seawater in traditional electrolyzers, is an energy-intensive and costly process. Even without desalination, the complex ion composition can increase the energy requirements for electrolysis compared to ultrapure water.
These hurdles have historically limited the industrial application and large-scale deployment of direct seawater electrolysis.
The Breakthrough: A Durable Carbon Cloth Electrode
Addressing these critical limitations, Dr. Ji-Hyung Han’s team at the Korea Institute of Energy Research (KIER) has made a significant advancement with a novel carbon cloth-based electrode. This innovative electrode has demonstrated unprecedented stability, maintaining a stable hydrogen output for over 800 hours (more than a month) under a high current density of 500 mA/cm², a performance threshold crucial for industrial viability.
The Role of Carbon Cloth and Optimized Treatment
Carbon cloth emerged as an ideal support material due to its inherent advantages, including excellent conductivity, superior corrosion resistance, flexibility, and cost-effectiveness compared to metal-based supports that quickly corrode in chloride-rich environments.
The key to the KIER team’s success lies in an optimized acid treatment process. They immersed the carbon cloth in a concentrated nitric acid solution at 100°C for one hour. This meticulous treatment:
- Enhances Hydrophilicity: Improves the water-attracting properties of the carbon cloth, ensuring better interaction with the seawater electrolyte.
- Promotes Uniform Catalyst Distribution: Facilitates the even distribution of catalyst materials across the electrode surface, leading to more efficient reactions.
The Advanced Catalyst: Ru-modified CoMo
Integral to the electrode’s remarkable performance is the incorporation of a ruthenium (Ru)-modified cobalt-molybdenum (CoMo) catalyst. Despite using only about 1% ruthenium by weight, this advanced catalyst significantly reduces the overpotential required for the hydrogen evolution reaction (HER), making the process approximately 1.3 times more efficient at equivalent current densities. This improved efficiency directly translates to lower energy consumption for hydrogen production.
Overcoming Seawater’s Major Hurdles
The KIER electrode’s design directly addresses the primary challenges of seawater electrolysis:
- Corrosion Resistance: The combination of corrosion-resistant carbon cloth and the specific catalyst formulation provides outstanding durability against the corrosive effects of chloride ions. Post-operation evaluations confirmed no significant leaching of metal ions into the electrolyte, demonstrating the electrode’s superb corrosion resistance and structural integrity.
- Mitigating Side Reactions: By optimizing the surface chemistry and catalytic activity, the electrode minimizes the undesirable chlorine evolution reaction, ensuring cleaner hydrogen production and preventing electrode poisoning.
- Sustained Performance: The 800-hour stable operation under industrial current densities signifies a major leap in overcoming performance degradation issues caused by ion precipitation and competitive reactions, which have plagued previous attempts at direct seawater electrolysis.
Implications for the Future of Green Hydrogen
This breakthrough holds profound implications for the global energy landscape:
- Sustainable Hydrogen Production: By enabling direct hydrogen production from seawater, the technology offers a truly sustainable pathway for green hydrogen, decoupling its generation from the dwindling freshwater supply.
- Reduced Costs: Eliminating the need for expensive and energy-intensive desalination processes can drastically reduce the capital and operational costs associated with green hydrogen production, making it more economically viable.
- Decentralized Production: The feasibility of using seawater opens up possibilities for decentralized hydrogen production facilities, particularly in coastal and island regions abundant in seawater and renewable energy sources like offshore wind or solar.
- Enhanced Energy Security: Countries with limited freshwater but extensive coastlines could leverage this technology to achieve greater energy independence.
Future Outlook and Scalability
While the 800-hour demonstration is a significant laboratory achievement, the research team is now focused on translating this success to larger scales. Efforts are underway to move from lab-scale to pilot-scale testing, aiming to validate the technology under real-world outdoor conditions. The ultimate goal includes developing modular hydrogen generators powered by renewable energy, specifically tailored for deployment in arid coastal regions.
The durable carbon cloth electrode developed by the KIER team represents a monumental stride in the quest for clean, abundant, and sustainable hydrogen. By addressing long-standing challenges in seawater electrolysis, this innovation paves the way for a future where the world’s oceans become a primary, inexhaustible source of green hydrogen, accelerating the global transition to a carbon-neutral economy.
