FeNC@nitrogen doped porous carbon leaf-carbon nanotube hybrids for oxygen reduction reaction

A series of nitrogen doped porous carbon leaf-carbon nanotubes incorporated FeNx electrocatalysts (FeNC@NCLCNT) are prepared by pyrolysis of Fe doped leaf-like Zn-zeolitic imidazolate framework (FeZn-ZIF-L) with different Fe contents. Among the catalysts, FeNC@NCL-CNT-3 exhibits the highest ORR activity in alkaline solution with onset potential (Eonset) of 0.95 V, half-wave potential (E1/2) of 0.81 V, and limiting diffusion current density of 6.14 mA cm-2. The Eonset and E1/2 of FeNC@NCL-CNT-3 are positively shifted by ca. 20 and 6 mV, respectively compared with Pt/C. The self-generated CNT caused by Fe catalysis improves the electronic conductivity and enlarges the average pore size of the catalyst from 1.77 to 8.12 nm. The highest density of pyridineN and Fe-Nx active sites (50.7 %) and the largest electrochemically active surface area (ECSA, 1075 cm2) also contribute to its superior activity. The Tafel slope of FeNC@NCL-CNT-3 is 75.4 mV dec-1, which is close to that of Pt/C. Fe-NCL/CNT-3 shows excellent long-term stability (99.4 % retention) and superior methanol tolerance. It catalyzes ORR through 4e- path.