Fe/Fe₃C-NC Nanosheet/Carbon Nanotube Composite Electrocatalysts for Oxygen Reduction Reaction

The construction of active and durable electrocatalysts based on a high abundance of elements toward oxygen reduction reaction (ORR) is critical for proton-exchange membrane fuel cells and metal–air batteries. Here, a composite nanostructure composed of Fe/Fe3C-NC nanosheets and carbon nanotubes (G-Fe/Fe3C-NC/CNTs) was designed by simply annealing a glucose-chelated Fe-coordinated metal–organic frameworks. The introduction of glucose can not only effectively prevent the collapse of the initial two-dimensional (2D) leaflike zeolitic imidazolate frameworks (ZIFs) during the carbonization process but also boost the growth of carbon nanotubes (CNTs). Benefiting from efficient Fe/Fe3C and Fe–Nx moieties, high specific surface area, and electron-conducting highways provided by the unique composite structure, the obtained G-Fe/Fe3C-NC/CNTs electrocatalysts achieved an impressive ORR activity with a higher positive onset potential of 1.02 V and half-wave potential of 0.87 V over the commercial Pt/C. Significantly, it also exhibits outstanding stability after 6000 cyclic voltammogram (CV) cycles with nearly negligible decay in half-wave potential, which makes it one of the promising Pt-free catalysts for ORR.