Development of PEMFC Catalyst Layers with Low-Pt Loading Utilizing Stream-Jet Coating Technology
Authors: Cho Hyun A , Lee Sang-Ho , Lim Sung Nam , Woo Ju Young , Song Shin Ae 
Published: December 2024

Global warming is one of the most serious problems we currently face. International efforts to reduce greenhouse gas emissions and achieve carbon neutrality are crucial for addressing this issue. As a result, the importance of hydrogen fuel cells, which are eco-friendly and capable of producing clean energy, is becoming more prominent. In particular, polymer electrolyte membrane fuel cells (PEMFC) are attracting attention as next-generation energy that can be applied to various industrial fields such as portable and transportation applications due to their efficient energy density and ability to operate at low temperatures. However, the high price of PEMFC membrane-electrode assembly (MEA) using Pt catalysts is a major issue that increases the cost of fuel cell systems and makes commercialization difficult. Therefore, reducing Pt usage, improving cell performance, and simplifying the MEA manufacturing process have become important research and development directions for PEMFC. As part of these efforts, various catalyst layer coating methods such as ultrasonic spraying, inkjet printing, and doctor blade are being studied. However, although ultrasonic spray coating has the advantage of a simple process, it has the problem of slow coating speed, making it difficult to manufacture large-area MEA [1]. On the other hand, doctor blade coating is suitable for mass production with high precision and fast coating speed, so it is mainly used in commercial MEAs. However, it is difficult to form thin film coatings due to the characteristic of using a highly concentrated solution [1, 2].
In this study, a new coating technology using the stream-jet technique was introduced to reduce Pt usage and simultaneously fabricate large-area MEA. This technique is a method of coating by continuously spraying a solution through a micro nozzle using external pneumatic pressure. It has a fast coating speed with the micro nozzle moving at a speed of up to 1 m/s [3]. The stream-jet coating method with these characteristics is expected to be an advantageous coating technology for large-area PEMFC MEA manufacturing and future commercialization. Moreover, the micro nozzle moves in the X-axis direction, and the stage on which the sample is placed moves in the Y-axis direction to coat the electrode in the desired area. In this process, the amount of Pt used can be controlled by adjusting the printing interval and coating frequency of the stage moving in the Y-axis direction. Solutions of various concentration ranges can also be used to form a uniform thin film coating catalyst layer. Through this technology, we fabricated a MEA that effectively reduced Pt usage by coating a very thin catalyst layer of less than 5 um using a catalyst ink with a low concentration of less than 1 wt%. The Pt loading of the cathode was fixed at 0.11 ± 0.01 mgpt/cm2, and by using a low concentration solution, the anode Pt loading could be reduced to 0.025 ± 0.001 mgpt/cm2 without significant performance loss in the range of low current density. Additionally, it was confirmed that a catalyst layer with an area of 25 cm2 could be coated within a few seconds due to the fast coating speed. MEAs fabricated with stream-jet coating were compared for single-cell performance with commercial MEAs. As a result, it was confirmed that the performance of cells using stream-jet coating technology showed high mass activity performance compared to the Pt loading. This achievement is believed to be a technology that can secure the price competitiveness of fuel cells through stream-jet coating technology and contribute to the development of large-area MEA.

Acknowledgements

This work was supported by the Ministry of Trade, Industry & Energy (MOTIE, Korea) and the Korea Evaluation Institute of Industrial Technology (KEIT). (Grant No.20019249)

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