Analysis of Mechanism of Nafion Conductivity Change Due to Hot Pressing Treatment

Proton Exchange Membrane Fuel Cells (PEMFC) are an emerging alternative energy source that

provide high power density with only heat and water as waste products. A current challenge of

making PEMFC technology broadly available is the performance losses and the cost of the

membrane electrode assembly (MEA). The group previously observed that performing repeated

hot‐pressing treatments on the PEMFC membrane, Nafion® 212, significantly increased the

performance of the cell. The mechanism of these performance improvements was investigated

by using various analytical techniques on samples subjected to different hot‐pressing

treatments. The effect of hot‐presses on proton conductivity was investigated with

Electrochemical Impedance Spectroscopy (EIS) measurements, which was used to separate and

quantify the different sources of polarization for the fuel cell. To determine if the increased

performance was a result of a chemical change, Thermogravimetric Analysis (TGA) and Fourier

Transform Infrared Spectroscopy (FTIR) were performed. Results indicate that hot pressing the

membrane significantly affected the electrical properties of Nafion® 212, illustrated through the

decreased series resistance in EIS measurements. However, TGA and FTIR measurements

demonstrated that the changes in Nafion® 212 were not chemical in nature. This study suggests

that hot pressing Nafion® 212 at the glass transition temperature causes an increase in proton

conductivity due to water channel reconfiguration in the membrane.