(Digital Presentation) Temperature-Dependent Study for Hydrogen Permeability of a Polymer Electrolyte Membrane Used in a PEFC

Abstract

Great efforts are currently underway to improve the performance of Polymer Electrolyte Fuel Cells (PEFCs) since they are potential devices to move on towards a carbon-free future. The Polymer Electrolyte Membrane (PEM) is crucial for the PEFC. It is the site where the exchange of protons between the anode and the cathode occurs to complete the energy conversion process. Also, operation temperature is one of the most critical parameters that significantly affect the internal reactions and thus the performance too. For this reason, it is essential to evaluate its performance at different temperatures. One useful technique is the linear sweep voltammetry (LSV) test. This technique allows knowing the hydrogen crossover that passes through the PEM and the existence of a short circuit. The determination of the hydrogen crossover is of great relevance since the conduction of electrons through the PEM causes a decrease in the fuel cell efficiency. Linear sweep voltammetry is an electrochemical method where the voltage is varied linearly as a function of time, and a current response is measured by a potentiostat. The analyzed single fuel cell features an effective area of 25 cm2, a polymer electrolyte membrane of Nafion® 112. The temperature was varied from 30 to 80 °C to cover the most common temperatures during operation, with a settled relative humidity at 100%. Hydrogen was used on the anode side and nitrogen on the cathode, with 0.1 L / min flow. The results show a proportional relationship between the crossover and the cell's operating temperature; with the data set, correlations were obtained using the fitting tool of Matlab, reaching an R-squared close to one. The correlations obtained can predict the crossover through the membrane as a function of the operating temperature. Furthermore, it was determined that the short-circuit value also increases as the temperature increases. Based on this, an optimal temperature range is identified to guarantee the membrane degradation and losing efficiency as slower as possible. Figure 1