Catalyst Layers with Blended Ionomer Using Short- and Long-Side Chain Dispersions

Hydrogen-based energy conversion technology is based on the membrane electrode assembly (MEA) comprising of an electrolyte and a pair of catalyst layers. It should have high efficiency and allow dynamic operation at low temperature. Electrochemical reactions for hydrogen oxidation reaction and oxygen reduction reaction occur in the catalyst layers in the MEA. Catalyst layers for MEA is prepared by catalyst inks comprising of electrocatalyst, ionomer dispersion and additional solvents. Ionomers plays an important roles for the formation of porous structure of catalyst layer for transportation of gas and reactant and for the ionic conduction. The ionomers are divided that long side chain (LSC) and short side chain (SSC) depending on the length of side chain. Long side chain (LSC) ionomers shows high performance at low temperatures and high humidity, while short side chain (SSC) ionomers shows high performance at high temperatures and low humidity. It has been reported that the properties of ionomer dispersions substantially influence the performance of catalyst layers due to the different interaction between electrocatalysts and ionomer. In this study, to investigate the effect of the properties of ionomer, various contents of blended ionomer dispersions were prepared. Properties of single and blended ionomers were characterized using catalysts layers in terms of I-V polarization, cyclic voltammetry, electrochemical impedance spectroscopy and microscopic evaluation such as porosimetry. Acknowledgment This research was supported in part by the Hydrogen Energy Innovation Technology Development Program of the National Research Foundation (NRF) funded by the Ministry of Science, ICT & Future Planning(NRF-2019M3E6A1063677) and by the New and Renewable Energy of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20213030040520).