Recent trends on the application of PGM-free catalysts at the cathode of anion exchange membrane fuel cells

Anion exchange membrane fuel cells (AEMFCs) are becoming more and more attractive due to their alkaline environment, being less aggressive and favorable to the use of low-cost materials. Furthermore, the alkaline medium displays enhanced alcohol oxidation reaction kinetics, which favors the use of fuels different from hydrogen, ranging from alcohols to polyols, and enhanced oxygen reduction reaction (ORR) kinetics. This allows the use of non-noble transition metals to synthesize cathodic catalysts, avoiding the costly platinum-group metals (PGM). In particular, the most active catalysts developed so far are mostly synthesized by sacrificial support method, which allows the fine tuning of the morphology, favoring oxygen transport, water removal, density of Fe-Ni-x active sites, and thus an enhanced electrochemical ORR activity. This mini-review analyzes the best AEMFCs cell performance achieved so far in recent years when PGM-free catalysts based on Me-N-C (Me = Fe, Co) are used for ORR at the cathode side, for AEMFCs fed with hydrogen, methanol, and ethanol.