Coupled soft-hard template-derived hierarchical porous Fe-N/C electrocatalysts facilitating efficient oxygen reduction in proton exchange membrane fuel cells

Due to the high energy conversion efficiency and environmental friendliness, proton exchange membrane fuel cells (PEMFCs) have attracted significant attentions for advancing clean energy technologies. However, the sluggish kinetics of the cathodic oxygen reduction reaction (ORR) severely limits the performance of PEMFCs. The high cost and poor durability of platinum-based electrocatalysts necessitate the development of alternative low-cost transition metal and N co-doped carbon (TM-N-C) catalysts. Nevertheless, the ORR activity of TM-N-C is limited by the low density of exposed active sites TM-N x on carbon. Herein, a combined high internal phase emulsion (HIPE) soft template and ZnO hard template is developed to fabricate porous Fe and N co-doped carbon (HP-Fe-N/C) catalyst. This coupled soft-hard template approach enables the construction of a hierarchical porous structure with high exposure of Fe-N x active sites and significantly promoted mass transport during ORR. The resultant HP-Fe-N/C demonstrates superior ORR electrocatalytic activity, achieving a high half-wave potential of 0.75 V in 0.1 M HClO 4 and 0.89 V in 0.1M KOH aqueous solution. When applied as a catalyst for the cathode of PEMFCs, the HP-Fe-N/C delivers a remarkable peak power density of 528.4 mW cm -2 and a high retention rate of 88.5% of its initial current density after working for 10 hours. This work provides a new approach for the fabrication of well-controlled hierarchical porous carbon-based electrocatalysts for the PEMFC.