Single‐atom catalysts (SACs) possessing well‐defined active sites of singular metal atoms have gained prominence in the field of electrocatalysis as they can be tuned to enhance activity and stability. In this study, a critical‐raw‐material (CRM)‐free SAC is synthesized for the oxygen reduction reaction (ORR) in alkaline media by pyrolyzing polyimide nanoparticles and Fe without using a sacrificial template. Upon purification, the resulting catalyst demonstrates outstanding performance as cathodes in anion‐exchange membrane fuel cells (AEMFCs) owing to sufficiently stabilized Fe single‐atoms at the FeN₄ sites yielding a peak power density (P_max) as high as ∼1.8 W cm⁻² and specific power values up to 11.3 W mg_PGM^-1; the latter being the greatest reported among CRM‐free cathode AEMFCs. The SAC also shows remarkable in situ durability under a very high current density of 1000 mA cm⁻², a first introduced here, with only a 2 mV h⁻¹ decay. Most impressively, when the SAC is combined with a NiMo anode to test a completely CRM‐free high‐temperature (HT)‐AEMFC at 118 °C, a P_max of 372 mW cm⁻² and limiting current density of ∼1.14 A cm⁻² are achieved. This work represents a significant milestone in the development of durable SAC cathode catalysts for the next generation of CRM‐free AEMFCs.

Single‐atom catalysts (SACs) possessing well‐defined active sites of singular metal atoms have gained prominence in the field of electrocatalysis as they can be tuned to enhance activity and stability. In this study, a critical‐raw‐material (CRM)‐free SAC is synthesized for the oxygen reduction reaction (ORR) in alkaline media by pyrolyzing polyimide nanoparticles and Fe without using a sacrificial template. Upon purification, the resulting catalyst demonstrates outstanding performance as cathodes in anion‐exchange membrane fuel cells (AEMFCs) owing to sufficiently stabilized Fe single‐atoms at the FeN₄ sites yielding a peak power density (P_max) as high as ∼1.8 W cm⁻² and specific power values up to 11.3 W mg_PGM^-1; the latter being the greatest reported among CRM‐free cathode AEMFCs. The SAC also shows remarkable in situ durability under a very high current density of 1000 mA cm⁻², a first introduced here, with only a 2 mV h⁻¹ decay. Most impressively, when the SAC is combined with a NiMo anode to test a completely CRM‐free high‐temperature (HT)‐AEMFC at 118 °C, a P_max of 372 mW cm⁻² and limiting current density of ∼1.14 A cm⁻² are achieved. This work represents a significant milestone in the development of durable SAC cathode catalysts for the next generation of CRM‐free AEMFCs.