Obstacles to Seawater Hydrogen Production Removed by Korean Researchers

Energy Technology Research Institute Successfully Suppresses Inorganic Precipitate Formation Caused by Seawater Acidification

Existing seawater electrolyzer (anion exchange membrane) - seawater alkalization progresses, forming dispersed inorganic precipitates. Photo by Korea Institute of Energy Research.

Acidification-Based Seawater Electrolyzer (Bipolar Membrane) - The acidification of seawater significantly suppresses the formation of dispersed inorganic precipitates, maintaining the seawater in a transparent state. Photo by Korea Institute of Energy Research

[Asia Economy Reporter Kim Bong-su] Domestic researchers have succeeded in removing obstacles to the commercialization of hydrogen production technology using seawater.

The Korea Institute of Energy Research announced on the 24th that Dr. Han Ji-hyung's marine convergence research team has secured a technology that completely suppresses dispersed inorganic precipitates by inducing seawater acidification when producing hydrogen directly from seawater, and reduces the growth rate of inorganic precipitates at the electrode interface, thereby improving the performance and stability of direct seawater electrolysis for the first time.

Major countries around the world are focusing all their efforts on developing 'water electrolysis' technology and expanding facilities to accelerate the hydrogen economy with zero greenhouse gas emissions to prevent global warming. In particular, water electrolysis facilities usually use ultra-pure purified water or 20-30% potassium hydroxide (KOH) solution without impurities as the electrolyte. Theoretically, producing 1 ton of hydrogen requires 9 tons of purified water, and obtaining 1 ton of purified water requires 2 tons of water. In other words, about 18 tons of water are needed to produce 1 ton of hydrogen.

However, direct seawater electrolysis technology, which uses the infinite water resource of seawater directly as the electrolyte to produce green hydrogen, is attracting attention as a technology that can minimize costs and environmental issues related to the electrolyte. It can significantly reduce capital expenditure (CAPEX) and operating expenditure (OPEX) for purification/desalination processes. It is environmentally friendly as it minimizes the carbon footprint in the production process of pure salt and potassium hydroxide required for alkaline water electrolysis.

The problem is that hydrogen is produced through the water reduction reaction at the cathode, and as seawater becomes alkaline, magnesium cations contained in seawater react to form inorganic precipitates. These inorganic precipitates greatly reduce the current density of seawater electrolysis and become an obstacle to the development of flow-based stacks, so a solution was needed.

The research team controlled inorganic precipitation by acidifying natural seawater without using additional chemicals, using a bipolar membrane as a separator where the water dissociation reaction (H2O → H+ + OH-) occurs. Since direct seawater electrolysis uses seawater as the electrolyte, it enables hydrogen production anywhere adjacent to the sea without restrictions on facilities required for seawater desalination and ultra-pure processes, contributing to the activation of the hydrogen economy. Furthermore, by presenting a method to solve the inorganic precipitation problem through this research, the possibility of developing direct seawater electrolysis stacks has increased, and marine green hydrogen production through a linked system with floating offshore wind platforms can be expected.

Dr. Han said, "The combination of a bipolar membrane (separator) and seawater (electrolyte) is the first case in electrochemical research, and we discovered a new phenomenon called seawater acidification," adding, "Through this research, we secured core technology that can improve the performance and stability of direct seawater electrolysis and greatly increased the possibility of developing large-capacity stacks."

The research results were published in the international journal in the field of chemical engineering, the Chemical Engineering Journal.

This content was produced with the assistance of AI translation services.