Iron and nitrogen co-modified multi-walled carbon nanotubes for efficient electrocatalytic oxygen reduction.

Multi-walled carbon nanotubes (MWCNTs) with one-dimensional nanostructure are an ideal support for oxygen reduction reaction (ORR) catalysts thanks to their intrinsic outstanding electrical conductivity and high specific surface area. Iron and nitrogen doping could alter the local electronic structure and therefore enhance the ORR activity of MWCNTs, but the preparation process always includes complicated growth conditions and post-treatment. Herein, an iron and nitrogen co-modified multi-walled carbon nanotubes (Fe-N-MWCNTs) with hierarchical nanostructure is engineered and synthesized via a simple two-step pyrolysis approach. Large specific surface area, low resistivity, and intensified charge density near the Fermi level synergistically endow the Fe-N-MWCNTs with outstanding ORR activity. The optimal Fe-N-MWCNTs exhibit a higher onset potential value of 0.92 V (versus RHE) and half-wave potential (E1/2) of 0.85 V (versus RHE) in 0.1 M KOH medium, which exceeds the benchmark Pt/C electrocatalyst (E1/2= 0.84 V). This strategy of modifying MWCNTs support by a simple calcination process provides a feasible method to prepare cost-efficient ORR electrocatalysts.