A technology has been developed that significantly improves the performance of electrolyzers that produce hydrogen. It is expected to bring us one step closer to commercializing green hydrogen production technology.

UNIST (President Yong-Hoon Lee) announced on the 21st that the research team led by Professor Young-Guk Kwon of the Department of Energy and Chemical Engineering (first author Tae-Hoon Kong, integrated master's and doctoral program researcher) has developed a 'membrane-catalyst-support integrated electrode manufacturing technology' that manufactures a membrane electrode assembly by directly growing a catalyst layer between an anion exchange membrane and a support.

Nickel and iron-based catalyst layers, which are representative catalysts that generate oxygen, were grown directly between the anion exchange membrane and the electrode support. The interfacial resistance was dramatically improved, and the performance of hydrogen production and the stability of the electrode catalyst were also enhanced.

Anion exchange membrane electrolysis technology is a system that produces hydrogen by using an exchange membrane that selectively moves only anions as an electrolyte. It is a system that complements the shortcomings of existing systems and maximizes their advantages, but improvements in performance and interfacial resistance are needed for commercialization.

The research team first moved BH4-, a strong reducing agent, through an 'anion exchange membrane' that only allows anions to pass. The research team grew an 'active catalyst layer' between the electrode support and the anion exchange membrane by inducing a reaction between the reducing agent that moved in this way and the metal ion.

The electrolytic cell utilizing the technology developed in this way showed an interface resistance that was twice as low as that of the conventional electrolytic cell. It showed excellent performance, showing a current density of 1 A/cm2 even at a cell voltage (1.79 V) that was about 100 mV lower than that of the conventional electrolytic cell in an alkaline environment of 50°C. In a driving test of over 400 hours, its stability was proven by showing a low deterioration rate (0.07㎷/h).

The research team revealed that the improved performance and stability were mainly due to the direct growth of the catalyst layer instead of the ionomer typically used in the membrane electrode assembly manufacturing process.

Ionomers serve to fix existing powder-type catalysts and deliver ions necessary for the reaction.

On the other hand, if used in excess, it can cause problems such as blocking the site where the catalyst reacts or reducing the emission of oxygen and hydrogen gases produced, resulting in catalyst detachment.

The developed technology improves both performance and stability by excluding the ionomer and directly growing the catalyst layer to optimize the membrane-catalyst-support interface.

Professor Kwon Young-guk of the Department of Energy and Chemical Engineering said, “Securing both the performance and stability of electrolyzers is essential for commercializing green hydrogen production technology,” and “We will develop core technologies to identify and resolve problems arising from the membrane electrode assembly, a key component of electrolyzers, and advance the realization of the hydrogen economy.”

The first author, Taehoon Gong, a researcher in the combined master's and doctoral program, said, "The existing membrane electrode assembly manufacturing technology had clear problems due to ionomers, so it was necessary to develop a technology to form a catalyst layer without ionomers." He added, "By introducing a chemical reduction method that utilizes the characteristics of anion exchange membranes, we developed a membrane electrode assembly manufacturing technology that improves both performance and stability."

This study was selected as the cover paper in 'ACS Energy Letters', a world-renowned journal in the field of energy and environmental science, and was published online on October 13 and in print on November 10. The research was conducted with the support of the mid-level project of the National Research Foundation of Korea under the Ministry of Science and ICT and the Energy Technology Development Project of the Ministry of Trade, Industry and Energy.