Hierarchically porous carbon with pentagon defects as highly efficient catalyst for oxygen reduction and oxygen evolution reactions

Highly dispersed electrocatalysts and single-atom catalysts receive extensive attention in the field of multiple reactions involving water spitting, oxygen reduction, and CO2 reduction. Herein, we develop a Fe/N co-doped hierarchically structured porous carbon (Fe/N/C-DT) by the dual-templating approach, involving the incorporation of ferrocenecarboxaldehyde (Fc-CHO) into the polyimide, followed by carbonization at 900 degrees C and etching. A steric hindrance offered by the ferrocene and the porosity of the obtained nanostructure prevent the aggregation of Fe atoms, resulting in the maximization of catalytic efficiency of iron-based sites. FeCl2/N/C-DT and FeSO4/N/C-DT using FeCl2 and FeSO4 as iron sources, respectively, are prepared for comparison, to further confirm the potential positive effect of Fc-CHO and explore the synergistic effect of the pentagon defects and Fe-N-4 on the catalytic performance in oxygen reduction reaction (ORR). The prepared Fe/N/C-DT exhibits outstanding electrochemical activity toward ORR (E-1/2 = 0.902 V vs RHE) and impressive OER activity (E-j=10 = 1.66 V) in alkaline conditions. The rechargeable Zn-air battery using Fe/N/C-DT as a cathode catalyst shows a peak power density of 220 mW cm(-2) and a high open-circuit voltage of 1.451 V in the all-solid-state Zn-air battery.