Facile synthesis of nitrogen and sulfur co-doped graphene-like carbon materials using methyl blue/montmorillonite composites

Abstract

Heteroatom-doped carbon materials are currently drawing increasing interest because they show remarkable performance when applied in lithium-ion batteries, supercapacitors, and fuel cells. In this work, a facile method was developed to synthesize N and S co-doped graphene-like carbon materials using montmorillonite (Mt) after the adsorption of methyl blue (MB). The MB–Mt composites were pyrolyzed in a N2 atmosphere to carbonize the adsorbed MB within the interspace of Mt. The resulting pyrolyzed carbon/Mt composite showed a basal spacing value of approximately 0.44 nm, close to the thickness of a single graphene sheet, suggesting the formation of graphene-like carbon materials within the interspace of Mt. Then, the carbon/Mt composite was demineralized by acid washing to liberate the carbon materials. Transmission electron microscopy and atomic force microscopy results directly showed the morphology of the resulting carbon material, i.e., the stacking of thin carbon sheets. Raman spectra showed the simultaneous presence of both a D-band and G-band for the obtained carbon materials, and their intensity ratio decreased with increasing pyrolysis temperature. X-ray photoelectron spectroscopy results indicated the presence of C, S, and N atoms in the carbon materials, and the doping sites of the S and N atoms were proposed. Finally, the obtained carbon materials showed interesting electrocatalytic activity for the oxygen reduction reaction, suggesting their potential application as efficient metal-free electrocatalysts in fuel cells. Our work synthesized N and S co-doped graphene-like materials with interesting electrocatalytic activity, which proved that the templated synthesis method could be a facile approach to synthesize various heteroatom-doped graphene-like carbon materials.