N, S-doped nanocarbon derived from ZIF-8 as a highly efficient and durable electro-catalyst for oxygen reduction reaction

Nitrogen and sulfur co-doped porous carbon (NSDPC) is successfully prepared by impregnation and carbonization using a zeolitic imidazolate framework-8 (ZIF-8), and it is employed as a catalyst for oxygen reduction reaction (ORR). The influences of carbonization temperature and doping densities on electrocatalytic activity for ORR are investigated. Doping densities of the nitrogen and sulfur are varied using various ratios of ZIF-8 to thiourea and optimized for the best performance for ORR. The synthesized carbon-based catalysts are physicochemically characterized by XRD, TGA, BET, SEM, and XPS. The resulting NSDPC materials exhibit enhanced ORR activity compared to pristine ZIF-8 and the samples after carbonization without doping. In addition, it shows excellent tolerance for methanol cross-over and higher cycling stability than those of commercial Pt/C. This improvement in the catalytic activity of NSDPC is attributed to the mesoporous structure and new active sites derived from the introduction of nitrogen and sulfur.