Co(II)-Chelated Polyimines as Oxygen Reduction Reaction Catalysts in Anion Exchange Membrane Fuel Cells

In this paper, a cobalt (Co)-chelated polynaphthalene imine (Co-PNIM) was calcined to become an oxygen reduction reaction (ORR) electrocatalyst (Co-N-C) as the cathode catalyst (CC) of an anion exchange membrane fuel cell (AEMFC). The X-ray diffraction pattern of CoNC-1000A900 illustrated that the carbon matrix develops clear C(002) and Co(111) planes after calcination, which was confirmed using high-resolution TEM pictures. Co-N-Cs also demonstrated a significant ORR peak at 0.8 V in a C-V (current vs. voltage) curve and produced an extremely limited reduction current density (5.46 mA cm^-2) comparable to commercial Pt/C catalysts (5.26 mA cm^-2). The measured halfway potential of Co-N-C (0.82 V) was even higher than that of Pt/C (0.81 V). The maximum power density (P_max) of the AEM single cell upon applying Co-N-C as the CC was 243 mW cm^-2, only slightly lower than that of Pt/C (280 mW cm^-2). The Tafel slope of CoNC-1000A900 (33.3 mV dec^-1) was lower than that of Pt/C (43.3 mV dec^-1). The limited reduction current density only decayed by 7.9% for CoNC-1000A900, compared to 22.7% for Pt/C, after 10,000 redox cycles.