Abstract
Polymer electrolyte fuel cells (PEFCs) have shown a great potential to be used in several applications, e.g., portable, mobile and stationary systems. Each of the mentioned applications demands from PEFCs different operating conditions to perform in the best possible manner. Knowing in detail the behavior of their internal components will help to improve the mechanical and thermal properties of the different constitutive layers. The objective of this research is to analyze in detail the behavior of the internal resistances of a PEFC, using the impedance spectroscopy technique. A single cell is evaluated in a broad range of current densities, i.e., from 0.2 to 2.0 A.cm-2, to evaluate the resistances that cause loss of performance. The analyzed resistances correspond to the ohmic, charge transfer and mass transport resistance. The results were obtained after the interpretation of the data taking from Nyquist diagrams, and they were analyzed considering high and low conditions of relative humidity. The obtained results showed that the ohmic resistance (attributed to membrane Nafion® 212), is independent of the load applied for fully humidified conditions, with a value of 0.0725 Ω.cm2. On the other hand, it is strongly dependent on low humidification conditions, with values between [ 0.198 – 0.132] Ω.cm2, for current density of [0.2 – 2.0] A.cm-2, respectively. It was also found that the charge transfer resistance decreases with respect to the applied load until a saturation value, and further it represents the major participation to the total resistance of the cell. The charge transfer resistance represents around 50 – 75% of the total resistance in conditions of high relative humidity, and among 30 – 65% for conditions of low relative humidity. In addition, it was found that the mass transport resistance appears early at low relative humidity and triples for full humidification conditions.
Highlights
The effects of the emission and excessive accumulation of carbon dioxide (CO2) gases in the atmosphere is a topic of great importance
The results obtained through electrochemical impedance spectroscopy (EIS) test revealed the behavior of the various voltage losses within the cell, which are attributed to ohmic resistance, charge transfer resistance and mass transport resistance
The ohmic resistance represents around 23–45% of the total resistance of the cell for high relative humidity (RH) and between 33 and 51% for low RH
Summary
The effects of the emission and excessive accumulation of carbon dioxide (CO2) gases in the atmosphere is a topic of great importance. Studies show that at the end of this century, our planet can reach the critical threshold causing a climatic disequilibrium that will seriously affect the life on the planet (Rothman, 2019). Under this scenario, the reduction of CO2 emissions plays an important role to stop or decrease the damage of our ecosystem. One of the devices with a great projection is the polymer electrolyte fuel cell (PEFC), which is an electrochemical device that convert the chemical energy present in the fuel into electrical energy and water in a clean manner.
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