A comprehensive analysis is conducted to evaluate the effect of organic solvent addition on catalyst ink preparation for 

polymer electrolyte membrane fuel cells (PEMFCs). Three ester-based organic solvents—methyl acetate (MAc), ethyl 

acetate (EAc), and methyl formate (MF)—are selected and added to catalyst inks using a mixed solvent system of water 

and alcohol. The surface area, homogeneity, and uniform particle size distribution of the catalyst powders are found to 

strongly influence ionomer adsorption behavior and dispersion stability, thereby suppressing particle agglomeration and 

enhancing the hydrophilicity of the electrode surface. Among the solvents, the catalyst ink containing MAc in a water/

isopropanol system exhibits superior homogeneity, improved dispersion characteristics, a reduced contact angle (116.0°), 

and a smaller average particle size (0.204 μm) compared to those prepared with other organic solvents. In addition, catalyst

inks containing 10% MAc show narrower particle size distributions both with and without ionomer, along with a 

reduced mesoporous band. As a result, the electrode fabricated from the MAc-containing catalyst ink achieves the highest 

electrochemical performance. These results clearly demonstrate that the controlled addition of MAc during catalyst ink 

preparation significantly enhances ink dispersion quality and PEMFC performance.