Membrane electrode assemblies (MEAs) were fabricated directly onto the electrolyte membrane, using an ultrasonic spraying technique. Pt–C catalysts, with concentrations of 10%, 20% and 40% by weight, were used, and the Pt loading onto the MEAs was kept constant at 0.3 mg cm−2. Nafion contents were considered from 15% to 35 wt.%. The morphologies of the MEAs were evaluated by scanning electron microscopy (SEM), in which the agglomeration of Pt–C particles was imaged, and a secondary pore in the catalyst layers (CLs) was revealed. The cross‐section images showed that the thickness of the CLs depended on the Pt–C concentration. The electrochemical surface area (ECSA) of those Pt–C concentrations and various compositions of Nafion contents were examined by cyclic voltammetry. Polarization curves were also measured and showed that the Nafion contents of 25 wt.%, 20 wt.%, and 15 wt.% gave the best performance for 10 wt.%, 20 wt.%, and 40 wt.% Pt–C catalysts, respectively. This indicates the Pt concentration is dependent on the Nafion content; the greater the weight of platinum in the catalysts, the less Nafion ionomer is required to optimize the electrochemical reaction. The data shows the same results regardless of the MEA fabrication techniques, operating conditions and Pt loadings.

Determining the optimal catalyst ink formula for manufacturing membrane electrode assemblies (MEAs) in proton exchange membrane (PEM) fuel cells is important to optimizing their performance. The proper catalyst inks maintain the optimal balance of mass and ion transport in the catalyst layers. Catalyst inks are composed mainly of a carrier, Nafion solution, and a Pt/C catalyst. We investigated the optimal catalyst ink formula by varying these components during fabrication of MEAs by 20-kHz ultrasonic spraying. Various carriers (isopropyl alcohol (IPA), tetrahydrofuran (THF), and ethanol) and Nafion concentrations were investigated when using Pt/C 20% catalyst with a constant Pt loading of 0.3 mg/cm 2 . The catalyst layers of the fabricated MEAs were analyzed using both in-plane and cross-sectional scanning electron microscopy (SEM) images. The thickness of the catalyst layer depended on the type of carrier, with IPA, THF, and ethanol yielding thicknesses of 28, 22, and 18 μm, respectively. Polarization curves were used to determine the fuel cell performance. MEAs fabricated with ethanol preformed better than with IPA or THF; yielding a current density of 697.02 mA/cm 2 at a cell potential of 0.6 V. The optimal Nafion concentration was 20, 25, and 30 wt% for ethanol, IPA, and THF, respectively.