Templated synthesis of nitrogen-doped graphene-like carbon materials using spent montmorillonite†
Abstract
Montmorillonite (Mt) as an environmentally-friendly, low-cost, and highly-efficient adsorbent for cationic dyes has a promising application in dye wastewater treatment. However, proper disposal of the spent Mt is still a challenge holding back the wide application of Mt. This article reports a simple method which can synthesize N-doped graphene-like carbon materials using the spent Mt after the adsorption of crystal violet (CV). The spent Mt was pyrolyzed under the protection of N2 to carbonize the adsorbed CV within the interlayer space of Mt, and the interlayer spacing of Mt decreased from 11.0 Å to approximately 3.6 Å, close to the thickness of a single graphene layer (3.4 Å). After demineralization (i.e., washing with a mixture of HF and HCl), the carbon material was released from the interlayer space of Mt. Raman spectra showed the presence of both the D-band and G-band on the obtained carbon materials, and transmission electron microscopy observed the thin layers of carbon material. X-ray photoelectron spectroscopy results indicated the simultaneous presence of pyridinic, pyrrolic, and quaternary N on the carbon materials. In addition, the percentage of pyridinic N increases with increasing pyrolysis temperature; whereas that of quaternary N decreases and of pyrrolic N remains relatively constant. The above results suggested the successful synthesis of N-doped graphene-like carbon material. Finally, the obtained materials show interesting electrocatalytic activity for the oxygen reduction reaction and show potential to be used as efficient metal-free electrocatalysts in fuel cells.
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