Professor Yi Sung-chul from the Department of Chemical Engineering at Hanyang University, Dr. Jung Chi-young from the Korea Institute of Energy Research, and their research team reported the fabrication of a Membrane Electrode Assembly (MEA, a key component of fuel cells for vehicles and buildings) with a very low loading/amount of platinum for fuel cell application. This new technology with its simplified manufacturing process not only can reduce the production cost but also open up opportunities for mass production of high-performance MEA.  The new MEA has even met the standard of 0.1 mg/cm2 or less of platinum used in fuel cells for vehicles, which is one of the prime technical targets of the U.S. Department of Energy (US DOE) set for 2025.   

Nowadays, the automotive and energy industry is going green by employing hydrogen-powered fuel cells, which implies that the tested and proven internal combustion engine will become a thing of the past over the next few decades.

In a typical manufacturing process of fuel cell electrodes, a catalyst ink in the form of slurry is prepared by mixing platinum (Pt) catalyst and Nafion binder. This mixture, however, tends to agglomerate during the dispersion, coating, and drying process, and as a result of this aggregation of forming a cluster, the oxygen transfer resistance is increased while catalyst activity is reduced.

To overcome these shortcomings, the researchers headed by Professor Yi designed an electrode with a new vertical architecture that possesses a very thin and uniform Nafion ionomer distribution by precisely controlling the ionomer to about 2 nanometers through a Hot-Humid ElectroSpray Deposition (HHESD) process. Because of their unique structure, the electrodes maximize fuel cell performance by vertically aligning the platinum catalysts, Nafion ionomers, and voids to optimize the movement distance of ions, electrons, and oxygen required for the reaction.

By employing the HHESD process, the electrical repulsion powered by high voltage aids in an adequate dispersion of catalysts and ionomers in the slurry. As a result of thinning and high dispersion of ionomers, the poisoning rate of catalyst is reduced, and the oxygen travel distance (20 – 30%) along with the utilization rate of platinum catalysts is maximized by more than three times compared to the conventionally made electrodes.

In addition, it is anticipated that the cost involved in mass-production can be reduced by half, as well as the speed of mass-production can be doubled up. This new technology involves the fabrication process of a direct membrane coating method wherein the catalyst ink is applied straightaway on the electrodes to polymer electrolyte membranes. Since the process is not complicated compared to the existing thick film coating method, the scalability to continuous mass-production lines is also exceptional.

The developed methodology has also addressed the hassle of water removal that is generated during fuel cell power generation when the ionomer content is lower in the existing thin-film electrode. It can realize water-repellent electrodes by controlling the shape of ionomers coated on electrodes in reverse micelle form and can improve operational performance and durability of fuel cells by easily removing water generated during power generation.  

Professor Yi said, "Through this research, we have secured a fundamental technology for producing next-generation electrodes that can reduce the unit price of MEAs for vehicles and buildings by more than 30 percent. By overcoming the existing thick film coating process to a direct film coating method, we expect that  it could make way for more feasible production of MEAs, thereby contributing to meeting the goal of fuel cell dissemination rate to realize carbon neutrality, which the government is promoting."

The research results were published in the international academic journal in the environmental engineering field Applied Catalysis B-Environmental online on August 10.