A defective 2D Fe–N–C nanofilm embedded with porous carbon derived from dicyandiamide as an effective oxygen reduction catalyst for PEMFCs

Abstract

Two-dimensional (2D) materials with high specific surface areas are considered promising precursors for creating highly effective Fe–N–C catalysts that improve the oxygen reduction reaction (ORR) activity, thereby lowering costs of the catalyst layer (CL) in proton exchange membrane fuel cells (PEMFCs). However, 2D materials tend to agglomerate while preparing the MEA, compromising PEMFC performance. In this study, we introduce an Fe–N–C catalyst using an ultrathin 2D N-doped carbon film (NCF) derived from a ZIF precursor through a metal salt-assisted pyrolysis approach. The active sites are fabricated via Fe^x+ adsorption and dicyandiamide (DCDA)-assisted pyrolysis. Adding DCDA improves the coordination environment of Fe and forms defects on the surface of the catalyst, promoting the exposure of the Fe active site. The porous carbon particles derived from DCDA result in hierarchical pores in the CL, promoting the utilization of active sites. The resulting catalyst (NCF-Fe-DCDA) exhibits superior ORR activity, achieving a half-wave potential (E_1/2) of 0.831 V_RHE under acidic conditions. The MEA equipped with the NCF-Fe-DCDA CL demonstrates low mass-transport overpotential and a remarkable power density of 845 mW cm⁻² under H₂/O₂ conditions. This research introduces an innovative approach for the synthesis of 2D Fe–N–C catalysts for PEMFC application.