Boosting the durability of Fe-N-C electrocatalysts for PEM fuel cells by dicyandiamide modification strategy

The insufficient stability of atomically-dispersed Fe-N-C electrocatalysts for oxygen reduction reaction (ORR) is still a major impediment to their practical deployment in proton exchange membrane fuel cells (PEMFC). Herein, we report a highly stable Fe-N-C electrocatalyst (Dicy/Fe-N-C) via dicyandiamide (DCDA) modification strategy. The Dicy/Fe-N-C electrocatalyst exhibits a distinguished durability in platinum group metal-free (PGM-free) PEMFCs, maintaining stable operation of 264 h under constant voltage (H2-Air, 100 kPa) and exhibiting a slight peak power density (PPD) loss of 23% after 30k cycles in accelerated durability tests (ADT). Density functional theory calculation reveals that the pyridinic FeN4 sites possess the highest energy barriers against demetallation and free-radical attack, compared to the pyrrolic and defect-rich pyrrolic FeN4 sites. The high stability of Dicy/Fe-N-C is ascribed to the fact that DCDA induces the formation of high stable pyridinic FeN4 sites and the reinforced graphitic carbon support, and simultaneously inhibits the generation of H2O2. Therefore, this work provides a new approach to develop robust PGM-free electrocatalyst for PEMFCs.