Molten-salt/oxalate mediating Fe and N-doped mesoporous carbon sheet nanostructures towards highly efficient and durable oxygen reduction electrocatalysis

Designer Fe-N/C-type oxygen reduction electrocatalysts with ultrahigh active-sites density and distinctive physical properties are recently considered to be a new frontier in energy technology. In this work, we creatively propose a new strategy for the controllable synthesis of iron and nitrogen co-doped mesoporous Fe-N/C-type graphene-like carbon nanosheet structures via NaCl template-assisted two-step calcination of iron coordinated with triazine compounds using potassium oxalate as a pore-activator. The synthesized Fe-N/C electrocatalyst exhibits unexpectedly ORR catalytic performance with a half-wave potential of ca. 0.846 V and an onset potential of ca. 1.02 V that compare favourably with the best Pt/C catalyst, but its electrochemical stability and methanol-tolerant property are more excellent. It is found that the unique mesoporous structure, the excellent electro-conductivity and the full exposure of N-doped catalytic sites (e.g., pyridinic-N, graphitic-N and Fe-Nx) of the gained Fe-N/C catalyst can facilitate the transport of electrolyte ions, reaction intermediates and products, maintain continuous electron-transport pathways, and minimize the agglomeration of catalytic sites to further boost the reaction rate and ORR activity. This study provides a new avenue to design high-performance and low-cost nanocarbon-based catalytic materials with dense active sites for some important reactions in new energy devices.