High oxygen-reduction activity and durability of nitrogen and sulfur dual doped porous carbon microspheres

Nitrogen and sulfur co-doped monodisperse carbon microspheres (NS-CMSs) have been successfully synthesized as a new kind of outstanding metal-free ORR catalyst through a one-pot solvothermal reaction. The as-synthesized heteroatom-doped CMSs have been systematically characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) and by using Raman spectra and nitrogen adsorption and desorption isotherms. Compared with the commercially available 20 wt% Pt/C catalyst, the as-prepared NS-CMSs showed a much better tolerance toward methanol crossover and long-term operation stability for ORR in an alkaline medium.