Effects of the cathode relative humidity on the performance of PEMFC withplatinum group metal-free cathode

Polymer electrolyte membrane fuel cells (PEMFCs) represent a promising sustainable energyconversion technology, due to their high energy efficiency and low emission. The oxygen reductionreaction (ORR) electrocatalyst and operating conditions (specifically cathode relative humidity) aretwo critical factors on the PEMFC performance. Challenges such as limited resources and the highprice of platinum and deactivation by CO poisoning, make it necessary to find proper replacements andin this regard, the production of carbon-based nonprecious metal electrocatalysts (NPMCs) by usingmetal-organic frameworks (MOFs) precursors has attracted much attention [۱- ۳]. The main positiveeffect of relative humidity on the efficiency of the PEMFC is due to the hydration of the Nafionmembrane and catalyst layer ionomer, which leads to an increase in the membrane proton conductivityand catalyst layer performance improvement [۴]. In addition, the relative humidity of reactant gases isalso effective on the electrochemical reactions kinetics (activation polarization) and the mass transferprocess [۵].Herein, to study the effect of cathode relative humidity on the PEMFC performance, a membraneelectrodeassembly (MEA) was fabricated according to a specific method and for the oxygen reductionreaction (ORR) in the cathode, the nonprecious metal electrocatalyst (Fe-NC/S,N-CNT) whichobtained by using MOF precursor (Fe-ZIF-PPY) was used [۶]. The performance of the fabricatedMEA has been evaluated in different values of cathode relative humidity (۳۰%, ۵۰%, and ۱۰۰%) in asingle cell by the fuel cell test station (BioLogic FCT-۱۵۰S) and electrochemical tests. Based on theobtained results, the optimal value of cathode relative humidity is ۱۰۰%, where the maximum powerdensity of ۱۰۷ mW/cm۲ was obtained.

Keywords:

Electrocatalyst , Hydrogen fuel , MOF , Operating condition , ORR , PEMFC