Iron-based nanoparticles embedded in nitrogen-doped carbon nanofibers towards efficient oxygen reduction for zinc-air batteries

Rational design of hybrid electrocatalysts of nanostructured non-precious metals/metal compound on highly conductive substrates is significant to enhance oxygen reduction activity for clean energy conversion. However, the limited exposure of active sites and sluggish mass transport on electrode trade-off the intrinsic performance of electrocatalyst. Herein, we report a strategic method to fabricate electrocatalyst with well-dispersed iron-based mixed nanoparticles embedding in nitrogen-doped carbon nanofibers (Fe-Fe3C/Fe3N@NCNFs) and demonstrate desired properties of the material, such as hierarchically porous structure, large specific surface area, and well-dispersion of mixed nanoparticles. The Fe-Fe3C/Fe3N@NCNFs electrocatalyst also exhibits high-performed activity in oxygen reduction reaction (ORR) with high onset potential of 0.998 V and half wave potential of 0.85 V, as well as high stability and methanol tolerance, which is even superior to benchmark performance of commercial Pt/C. In addition, a zinc-air battery assembled with Fe-Fe3C/Fe3N@NCNFs as the air cathode shows high open-circuit voltage (1.466 V), high specific capacities (778 mA h g(-1) at 5 mA cm(-2)), excellent reversibility and stability. The remarkable improvement of electrocatalytic performance validates paramount advantages, attributing from the inter-connected conduction network and well-dispersed active sites on carbon nanofiber surface, over mass transfer process and maximizing exposure of catalytic sites