Ultrahigh Oxygen Reduction Reaction Electrocatalytic Activity and Stability over Hierarchical Nanoporous N-doped...

Hierarchical nanoporous N-doped carbon ZNC-1000 was prepared by facile pyrolysis of well-designed nanosized ZIF-8 precursor with optimized reaction temperature and time. It possesses large surface areas leading to sufficient exposed electrochemical active sites. Meanwhile, its moderate graphitization degree and suitable nanosized hierarchical porosity distributions would lead to the sufficient interaction between O₂ and the electrocatalyst surface which would benefit the transports of electrons and the electrolyte ions for ORR. As an electrocatalyst for oxygen reduction reaction, the ZNC-1000 presents a better catalytic property than the commercial Pt/C with 6/1 mV positive shifts for onset/half-wave potentials and 1.567 mA cm^-2 larger for limiting current density respectively. The stability of ZNC-1000 is also much better than that of Pt/C with negative shifts of 0/-2 mV (vs 5/31 mV) for onset/half-wave potentials and 6.0% vs 29.2% loss of limiting current density after 5000 cycles of accelerated durability test, as well as the relative current of 87.5% vs 40.2% retention after 30,000 s continuous chronoamperometric operation.