Synergistic enhancement of nitrogen and sulfur co-doped graphene with carbon nanosphere insertion for the electrocatalytic oxygen reduction reaction

A carbon black incorporated nitrogen and sulfur co-doped graphene (NSGCB) nanocomposite has been synthesized through one-pot annealing of a precursor mixture containing graphene oxide, thiourea, and acidized carbon black (CB). The NSGCB shows excellent performance for the oxygen reduction reaction (ORR) with the onset and half-wave potentials at 0.96 V and 0.81 V (vs. RHE), respectively, which are significantly higher compared to those of the catalysts derived from only graphene (0.90 V and 0.76 V) or carbon nanospheres (0.82 V and 0.74 V). The enhanced catalytic activity of the NSGCB electrode could be attributed to the synergistic effect of N/S co-doping and the enlarged interlayer space resulted from the insertion of carbon nanospheres into the graphene sheets. The four-electron selectivity and the limiting current density of the NSGCB nanocomposite are comparable to those of the commercial Pt/C catalyst. Furthermore, the NSGCB nanocomposite is superior to Pt/C in terms of long-term durability and tolerance to methanol poisoning.