Agglomerate Size Tuning of Cathode Catalyst Layers Fabricated Using Electrospray Deposition and Its Effects on PEMFC Performance

Abstract The catalyst layers in proton-exchange membrane fuel cells comprise agglomerates of Pt/C and ionomers, and their size may affect the catalyst layer structure and electrochemical properties. However, it is difficult to vary the agglomerate size without changing the composition of the catalyst layer. This study investigated a method for modifying the agglomerate size during catalyst layer fabrication using electrospray deposition and evaluated its effect on cell performance through single-cell testing. The agglomerate size was measured by varying the needle diameter, ink flow rate, Pt/C concentration in the solvent, and solvent type. The results showed that the differences associated with solvent selection produced the largest changes in agglomerate size among the investigated parameters. At a common flow rate of 0.4 mL h–1, the mean agglomerate diameters obtained using methanol and 2-propanol were 146 and 376 nm, respectively. Scanning electron microscopy observations revealed the presence of relatively large pores in the catalyst layer prepared using 2-propanol. This layer exhibited superior oxygen transport characteristics and a higher power output than the methanol-based layer, particularly when air was supplied to the cathode. In contrast, the methanol-based layer produced a higher power output when pure oxygen was used. These results demonstrate that electrospray deposition can produce catalyst layers with different agglomerate sizes and pore structures without altering the catalyst layer composition, thereby changing their electrochemical and transport properties.