New approach of nitrogen and sulfur-doped graphene synthesis using dipyrrolemethane and their electrocatalytic activity for oxygen reduction in alkaline media

We have been prepared a series of heteroatoms (N and/or S) doped graphene in different ratios from various doping precursors (pyridine, thiophene and bithiophene combined separately with dipyrrolemethane and used as single N and/or S precursor) by thermal reaction. The as synthesized heteroatomsdoped graphene materials have also been characterized via transmission electron microscopy (TEM), Xray photoelectron spectroscopy (XPS), and Raman spectroscopy. The XPS and Raman investigations suggest a better dual-doping with higher conversion rate of graphitic-N and thermal reduction of oxygen into the graphene sheets. The electrochemical investigation reveals that the both N and S-doped graphene (S1N2-GN800 and S2N2-GN800) have better catalytic activity on oxygen reduction reaction (ORR) than only N-doped graphene (N-3-GN80 0) with the assistance of synergistic effect of dual-doping. Particularly, the high thermal treated final product, N and S dual-doped graphene (S2N2-GN1000) shows remarkable electrocatalytic activity towards the ORR which not only establishes a pathway of four-electron transfer reaction but also exhibits a better fuel selectivity and stability than that of commercially available 20wt% Pt/C electrode. (C) 2014 Elsevier B.V. All rights reserved.