Fabrication of MEA based on sulfonic acid functionalized carbon supported platinum nanoparticles for oxygen reduction reaction in PEMFCs

Abstract

The Nafion ionomer affects the efficiency of the platinum (Pt) catalyst by blocking the active sites thereby restricting the gas permeability of the catalyst layer; but, there is a limitation in the quantity of Nafion ionomer that needs to be added without affecting the cell performance. Sulfonation of carbon-supported catalysts as mixed electronic and protonic conductors has been reported to be an efficient way to increase the triple-phase boundaries. In order to improve the utilization and activity of cathodic catalysts in the oxygen reduction reaction (ORR), Pt nanoparticles were loaded on a mixture of Vulcan XC-72R and MWCNTs, which were functionalized in a mixture of 96% sulfuric acid and 4-aminobenzenesulfonic acid using sodium nitrite to produce intermediate diazonium salts from substituted anilines. The influence of sulfonation on the structural, surface, morphological and catalytic characteristics of the catalysts was explored using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and electrochemical techniques. The performance of the ORR was optimal under the following conditions: 75 wt% f-MWCNTs and 25 wt% f-Vulcan XC-72R (5%). The optimum loading of Nafion was found to be 15 wt% and the MEA was fabricated according to this Nafion loading which is lower than that of other MEAs. The maximum power density of MEA with the modified electrocatalyst was 1.6 times more than that of MEA with the unmodified electrocatalyst.