12. Fuel Cells and Battery Technology

In recent years, as increasing greenhouse gas emissions have led to global warming, natural disasters such as floods, droughts, and rising sea levels are becoming more frequent in many regions, and there is growing momentum for conflicts to increase in search for a peaceful life. COP28 adopted the Global Stock Take and measures to address climate change to assess global progress, Japan is also promoting efforts to contribute to decarbonization, aiming for carbon neutrality with a focus on energy conservation and the introduction of non-fossil energy sources. Japan promotes the spread of hydrogen-related products such as Ene-Farm and Fuel Cell Vehicle utilizing PEFCs, etc. to realize a hydrogen society. However, although the MEA, a component of the PEFC, uses Pt catalysts to accelerate the cell reaction, its high cost (46% of the PEFC stack price) inhabits its explosive widespread use. Reducing costs by reducing the use of platinum catalysts while maintaining performance is essential for the widespread use of PEFCs. Therefore, to reduce the amount of Pt catalyst in PEFCs, our laboratory has developed a 3D catalyst layer that can effectively utilize all Pt catalysts in the electrode using an inkjet printer since 2017. The previous study could enhance the cell performance by reducing the Pt use amount from the GDL side to the electrolyte side on the catalyst layer thickness direction. This study examined the effectiveness of 2-D catalyst layers on the cell performance with different ratios of ionomer to Pt catalyst within the same electrode. As a result, the 2D catalyst layer increased the I/C ratio from upstream to downstream had lower electron transport resistance and better performance than vice versa. Moreover, the performance was better when the I/C ratio was divided into three parts in the same electrode than when it was divided into four parts.