- Successfully applied the developed palladium membrane to eco-friendly ammonia synthesis driven directly by water instead of hydrogen gas
- Published in the world-renowned journal Advanced Science (IF 14.1) in June

A South Korean research team has developed an eco-friendly ammonia synthesis process that significantly reduces carbon emissions through innovative separation membrane technology.

The Korea Institute of Energy Research (KIER) found that a palladium membrane selectively transports hydrogen ions in water across the membrane and subsequently demonstrated the practical feasibility of this mechanism through application to the ammonia synthesis process.

A separation membrane generally serves to prevent reagents, products, and solvents in an electrochemical cell from mixing, while allowing the selective permeation of ions required for the target reaction. Polymeric membranes, such as ion-exchange membranes, thus far have been predominantly employed for this purpose.

Polymeric membranes possess narrow channels that facilitate water transport while also allowing the passage of ions. However, this ion transport often causes undesirable molecules to pass through as well. This crossover compromises the performance and stability of electrochemical devices. In conventional separation membranes, suppressing crossover often leads to a decreased ion transport rate; namely, there is an inherent trade-off between these two metrics.

The KIER research team successfully addressed this crossover issue by employing palladium membranes that selectively absorb hydrogen atoms, replacing conventional polymeric membranes. This mechanism is characterized by a highly dense palladium membrane that selectively absorbs and transports hydrogen atoms across the membrane, while effectively preventing the crossover of all other chemical species.

Once an electric field is applied, hydrogen ions at one side of the palladium membrane are converted to hydrogen atoms. Subsequently, these atoms diffuse through the metallic matrix to the opposite side of the membrane, where they are converted back into hydrogen ions and discharged into the solution. During this process, the solvents, reagents, and products on either side remain effectively separated by the palladium membrane.

The KIER research team applied the developed palladium membrane technology to electrochemical ammonia synthesis, in collaboration with a research team led by Professor Yun Jeong Hwang at Seoul National University. Electrochemical ammonia synthesis is an environmentally friendly process that extracts hydrogen ions, a key feedstock, from water instead of fossil fuels. Furthermore, the process is powered by renewable energy, thereby minimizing carbon emissions.

Electrochemical synthesis of ammonia requires the selective transport of hydrogen ions, rather than water, into the organic solvent compartment where the actual synthesis takes place. Even trace amounts of water can significantly compromise the synthesis efficiency. However, in the absence of a viable technology to selectively transport hydrogen ions without water, hydrogen gas—rather than water—has predominantly been used as the feedstock.

Exploiting the newly developed palladium membrane technology, the KIER research team has, for the first time in Korea, successfully implemented an electrochemical ammonia synthesis process that directly utilizes water instead of hydrogen gas, offering a new research direction in this field.

Dr. Jae-Hyung Kim, who led the project, said, "This achievement is significant in that our proposed novel ion-transport mechanism provides an effective solution to the crossover issue, which remains a primary barrier to implementing green ammonia synthesis through electrochemical devices." Dr. Kim emphasized, "The developed technology also holds high potential for broader applications across various electrochemical devices that demand even stricter mass separation than ammonia synthesis."

This research was supported by the Global TOP Strategic Research Initiative through the National Research Council of Science & Technology (NST), with key findings published this June in the prestigious journal Advanced Science (IF 14.1).