Metastable Fe-Co/NC electrocatalysts engineered by ultrafast 500 °C Joule-heating: a break from the high-temperature paradigm for superior ORR

We breakthrough the conventional high-temperature paradigm for synthesizing transition metal catalysts by discovering 500 °C as a critical metastable window in ultrafast (>1500 °C/s) Joule heating synthesis. This kinetically confined thermal shock at precisely 500 °C uniquely terminates metal aggregation while locking abundant pyridinic-N sites (2.86 at.%) that effectively anchor highly dispersed Fe and Co species, simultaneously sculpting a defect-rich carbon matrix. This unique combination, inaccessible in traditional pyrolysis, unlocks exceptional synergistic activity. Consequently, the 500 °C-engineered NC-FeCo catalyst achieves an oxygen reduction record: half-wave potential (0.92 V) surpassing Pt/C (0.85 V) and 1500 °C-treated analogs (0.85 V), while delivering near-theoretical 4e − selectivity (<1.2% H₂O₂), negligible decay (ΔE = 3 mV/5000 cycles), and superior methanol tolerance. Our work establishes sub-second 500 °C thermal shock as an innovative platform for metastable dual-metal electrocatalysis.