Research conducted by Shuhei Yoshino et al. has been published in ACS Applied Materials & Interfaces.
Amid efforts to achieve a carbon–neutral society, fuel cells that generate electricity from hydrogen are attracting growing interest. Polymer electrolyte fuel cells, in particular, operate at relatively low temperatures and can deliver high power output, making them promising power sources for passenger and commercial vehicles. Because their electrodes require platinum, a precious metal, efficient electrode manufacturing technologies are needed to minimize platinum use without compromising fuel cell performance.
Fuel cell electrodes are fabricated by coating and drying a catalyst ink. The ink contains catalyst particles, which consist of carbon particles supporting platinum nanoparticles, as well as a proton-conducting polymer called an ionomer and solvents. In the ink, the ionomer adsorbs onto the surfaces of the catalyst particles. The amount adsorbed affects how the particles aggregate in the ink and the structure of the catalyst layer after drying, including its pore structure and proton transport pathways. Understanding and controlling ionomer adsorption behavior is therefore important. However, the amount adsorbed depends on multiple factors, including the surface properties and aggregate structure of the carbon particles and the platinum weight ratio. Even carbon particles with similar surface areas can adsorb different amounts of ionomer, making it difficult to determine the effect of each factor separately.
In this study, we systematically investigated the relationships between ionomer adsorption and multiple properties of the catalyst particles, including the surface area, aggregate structure, and surface chemistry of the carbon particles, as well as the platinum weight ratio. Based on the results, we developed a unified model describing ionomer adsorption. We then compared ionomer adsorption values calculated by the model with experimental measurements for 24 types of catalyst particles with different properties and found good agreement. These results demonstrate that the effects of multiple catalyst-particle properties on ionomer adsorption can be quantitatively compared.
The findings are expected to deepen our understanding of interactions among materials in catalyst inks and provide fundamental guidelines for the design of materials used in catalyst inks and catalyst layers.
Title: Structural Factors of Platinum-Supported Carbon Influencing Ionomer Adsorption in Fuel Cell Catalyst Inks
Authors: Yoshino, S., Harada, M., Hasegawa, N., Yomo, S., Koiwai, A., Minami, S., Yamakawa, S., Jinnouchi, R.
Journal Name: ACS Applied Materials & Interfaces
Published: January 28, 2026