Transformation of Metal-Organic Frameworks into Huge-Diameter Carbon Nanotubes with High Performance in Proton Exchange Membrane Fuel Cells.

Herein, we report an efficient strategy to transfer metal organic frameworks into huge-diameter carbon nanotubes (CNTs) at high production by using Fe-citrate-functionalized zeolitic imidazolium frameworks-8 (ZIF-8) as precursors. The constructed porous Fe-N-decorated CNTs represent a tube diameter of >0.1 μm and a length of >5 μm. We find that the use of Fe-citrate could not only facilitate the agglomeration of Fe to generate huge-diameter CNTs by the bottom-up organic strategy but also induce the formation of Fe-N sites by the ligand substitution of 2-methylimidazole with citrate ions in ZIF-8, making it a promising class of Pt-alternative catalysts for oxygen reduction reaction (ORR). Such an ideal architecture is endowed with highly intrinsic activity from Fe-N and the faster mass transport from huge-diameter tubes, leading to an excellent ORR performance with a maximum power density of 665 mW cm-2.