Nitrogen and Sulfur Dual-Doped Reduced Graphene Oxide: Synergistic Effect of Dopants Towards Oxygen Reduction Reaction

Abstract

We describe a facile single-step non-hydrothermal chemical route for the synthesis of N and S dual-doped reduced graphene oxide (SN-rGO) and the synergistic effect of N and S in oxygen reduction reaction (ORR). The reduction of graphene oxide (GO) and dual doping of rGO are achieved in one-step with a single doping agent in ethylene glycol. SN-rGO has pyridinic and pyrrolic nitrogen and thiophenic sulphur and it has N/C and S/C atomic ratio of 0.12 and 0.08, respectively. The atomic percentage of pyridinic N (66%) is significantly higher than pyrrolic N (34%). The electrocatalytic performance of SN-rGO towards ORR is examined in terms of onset potential, kinetic current density, number of electrons transferred, durability and methanol tolerance in alkaline solution. SN-rGO shows excellent electrocatalytic activity with an onset potential of −15mV (Hg/HgO) and it tends promotes the four electron pathway. The activity of SN-rGO is superior to that of rGO doped only with N and S (N-rGO and S-rGO) and undoped rGO. The comparison of the ORR activity of SN-rGO with N-rGO and S-rGO indicates the synergistic effect of heteroatoms of SN-rGO in the electrocatalytic reaction. SN-rGO is highly durable and completely silent towards the anode fuel methanol.