Metal-free carbon semi-tubes for oxygen reduction electrocatalysis

New carbon morphologies are desirable in the development of high-performance carbon-based electrocatalysts for cathodic oxygen reduction reaction (ORR) of polymer electrolyte membrane fuel cells. In this work, a carbon semi-tube (CST) is successfully constructed by polymerizing m-phenylenediamine (mPDA) using surfactant-assembled micelles as a soft template. After pyrolysis, the CST morphology is retained in the formed N-doped CST (N-CST) catalyst. This mPDA-induced catalyst can provide rich micropores, high N-content, and good conductivity, imbuing it with superior catalytic ORR activity, stability, and methanol tolerance to the commercial Pt/C catalyst. By using such a metal-free N-CST as a cathode catalyst, an alkaline polymer electrolyte fuel cell exhibits a maximum power density of about 200 mW cm−2. Furthermore, density functional theory (DFT) calculations suggest that high curvature can be greatly conducive to the excellent catalytic ORR activity by the induced strong OOH∗ adsorption on active sites through a strong dipole-electric field interaction.