Nitrogen-Doped Hierarchical Porous Hollow Carbon Microspheres for Electrochemical Energy Conversion

Abstract

Nitrogen-doped hierarchical porous hollow carbon microspheres (N-HPHCS) are synthesized using melamine-formaldehyde (MF) resin as carbon and nitrogen sources, sulfonated polystyrene microspheres (SPS) as the core template, and SiO₂ nanoparticles as the mesopore forming agent. The obtained microspheres are composed of SPS core and MF/SiO₂ composite shell (SPS@MF/SiO₂). This SPS@MF/SiO₂ is then calcined and acid-treated to obtain N-HPHCS. During the calcination, SPS core is removed, and the micropores are formed on the shell owing to the thermal decomposition of the MF resin. After chemical etching of the SiO₂ nanoparticles, mesopores are generated on the carbon shell. The as-prepared sample of N-HPHCS has high surface area and large pore volume, and exhibits catalytic activity toward oxygen reduction reaction (ORR). The electrocatalytic performance of N-HPHCS can be ascribed not only to the doped nitrogen atoms, but also to the hierarchical porous structure.