Molten NaCl assisted pyrolysis of ZIF-8/PAN electrospun fibers to synthesis 1D cross-linked mesoporous N-rich carbon as oxygen reduction electrocatalysts

Abstract

Controllable preparation of cross-linked mesoporous carbon materials on a large scale remains challenging. In the present work, a simple NaCl-assisted pyrolysis strategy is proposed here to efficiently convert closed pores into open pores in the pyrolysis products of 2-methylimidazole zinc salt nanoparticles/polyacrylonitrile (ZIF-8/PAN) electrospun fibers to prepare 1D cross-linked mesoporous N-rich carbon-based oxygen reduction reaction (ORR) electrocatalyst. The total specific surface area of micropores and mesopores was significantly increased from 162 m2/g to 1069 m2/g (mesopores: 704 m2/g). The ORR catalytic activity of open pore was superior to that of closed pore with more positive onset potential (0.96 vs. 0.85 V) and half-wave potential (0.79 vs. 0.72 V), larger limiting current density (5.23 vs. 3.62 mA cm−2) and electron transfer number (3.89 vs. 3.15). Such enhanced performance was attributed to the transformation from closed to open pores which greatly improved the mass transfer performance and the number of active sites.