LAUSR

N-doped carbon nanohorns filled with Fe nanoparticles (Fe-N-CNHs) were produced by one-step positive pressure-assisted arc discharge in the Ar and N2 mixture. After oxidation treatments in air, Fe was converted into Fe2O3, and nanopores were opened on CNHs from 1 to 5 nm controlled by oxidation temperature. Fe-N-CNHs oxidized in O2 at 550 °C (Fe2O3-N-CNH550ox) show 245 mV at 20 mA cm-1, which is much smaller than that of the ones oxidized at 500 °C (Fe2O3-N-CNH500ox), contributing to the larger pore size on CNHs (3-5 nm vs 2-3 nm) and a larger number of nanopores caused by the enhanced sidewall nanopores. However, the stability of Fe2O3-N-CNH550ox becomes much poorer than that of Fe2O3-N-CNH500ox after 2000 cycles. The unique relationship between the overpotential and long-term stability can be explained by the consideration of the size of Fe2O3 nanoparticles and nanopores on CNHs. Furthermore, the stability for Fe2O3-N-CNH550ox can be rapidly increased after heat treatment in Ar for 1 h caused by shrinking the size of tip nanopores. Herein, we first reveal that the performance of OER is related to the nanopore size of carbon carriers and the catalyst of nanometal particles. The optimization of pore-opening conditions in carbon carriers can be achieved a superior electrocatalytic OER performance, including a low overpotential at high current density and long-term stability.