Hollow and mesoporous lipstick-like nitrogen-doped carbon with incremented catalytic activity for oxygen reduction...

Hollow structure and pore size are considered to be crucial to the performance of nitrogen-doped carbon materials. In this paper, a lipstick-like hollow and mesoporous nitrogen-doped carbon (HNC-1000) material is prepared using a bottom-up template participation strategy. The images by scanning electron microscopy and transmission electron microscopy show that the precursor ZnO particles, the intermediate ZnO@ZIF-8 core-shell particles, and the target HNC-1000 particles all maintain a lipstick-like morphology, and HNC-1000 is a hollow nitrogen-doped carbon material. The specific surface area and pore size analyses show that the synthesized HNC-1000 has a very rich mesoporous structure with Vmeso+macro/Vtotal of 94.8% and mean mesopore size at 13.67 nm. X-ray photoelectron spectroscopy results show that the nitrogen in the catalyst HNC-1000 is mainly pyridine nitrogen and graphite nitrogen. The prepared HNC-1000 has excellent ORR catalytic activity with onset potential (0.98 V versus RHE), half-wave potential (0.85 V versus RHE), and limiting current density (5.51 mA cm^-2), which is comparable to that of commercial Pt/C (20 wt%) and superior to NC-1000 derived from pristine ZIF-8. HNC-1000 also has good stability and strong methanol tolerance, which is superior to commercial Pt/C catalyst. The improved performance of HNC-1000 is attributed to its hollow and mesoporous morphology. These findings demonstrate a stratage for the rational design and synthesis of practical electrocatalysts.