CoFe nanoparticles dispersed in Co/Fe-N-C support with meso- and macroporous structures as the high-performance catalyst boosting the oxygen reduction reaction for Al/Mg-air batteries

Constructing the M-N-C (M = Fe, Co, etc.) with meso- and macroporous structures is an effective strategy for designing the high-performance catalysts towards oxygen reduction reaction (ORR). However, these structures can hardly be achieved via the pyrolysis of classic metal-organic frameworks. Herein, we prepare the CoFe nanoparticles with surface oxides dispersed in Co/Fe-N-C support via carbonizing melamine and ethylenediaminetetraacetic acid chelated with metal ions. This hybrid exhibits high proportions of meso- and macropores along with excellent ORR catalytic activity, as evidenced by the half-wave potentials of 0.91 and 0.61 V (vs. RHE) in 0.1 M KOH and 3.5 wt% NaCl, respectively. The Al/Mg-air batteries with this catalyst exhibit superior performance to those employing Pt/C, primarily derived from the enlarged pore diameters and the exposed ORR active sites substantially enhancing the air-electrode performance. Our study provides an avenue to broaden the pore sizes of M-N-C for boosting its ORR catalytic activity.