Evaluation of the performance and detection of the oxygen reduction reaction kinetics of metal doped imine framework in proton exchange membrane fuel cells

Fe/N/C based catalysts are the best positioned ones to replace the state-of-the-art Pt-based catalysts for the oxygen reduction reaction (ORR) in Proton Exchange Membrane Fuel Cells (PEMFCs). Here, a Fe/N/C catalyst characterized by a high N/C ratio, has been synthesized from the pyrolysis of a N-rich imine-based polymer. In acidic electrolyte (0.1 M HClO 4 ) the catalyst demonstrates notable ORR activity with E onset and E 1/2 values of 1.09 and 0.77 V vs. RHE, respectively. Furthermore, the catalyst’s performance has been assessed in a single cell PEMFC setup. The optimization of the membrane electrode assembly (MEA) with the Fe/N/C catalyst entails examining various ionomer to catalyst ratios (I/C) as well as two coating methods: spray coating and drop casting. The optimized MEA achieved a cell performance of 725 mA cm −2 at 0.3 V and a power density close to 220 mW cm −2 . In order to understand the factors influencing PEMFC polarisation curves, electrochemical impedance spectroscopy (EIS) was performed under potentiostatic conditions. The effect of operational parameters, such as ionomer to catalyst ratios (I/C) and the use of either O 2 or air at the anode feed, has been investigated. EIS spectra allow the calculation of the distribution of relaxation times (DRT), providing insights into the rate and resistance of the ORR process occurring at the MEA. Notably, the cathode with an I/C= 2, prepared by drop casting, exhibited superior performance attributed to reduced ORR resistances. The current density and power density reached with the 25 cm 2 MEA are comparable to those obtained with the 5 cm 2 MEA using O 2 as cathode reactant. • The distribution of relaxation times (DRT) was calculated from EIS spectra. • The effect of several operating conditions on PEMFC performance was evaluated. • ORR rate and resistance in the PEMFC were analysed from the DRT data. • MEAs with ionomer to catalyst ratio of 2 by drop casting led to lower ORR resistances. • Performance of 25 cm 2 MEA comparable to that obtained with 5 cm 2 MEA using O 2.