Synthesis, Structure and Electronic Properties of Graphitic Carbon Nitride Films

Abstract

Dark-colored shiny flakes of graphitic carbon nitride materials produced by reacting dicyandiamide C2N4H4 in a KBr/LiBr molten salt medium were determined to have a C/N ratio near 1.2:1. The compounds also contained 2.3–2.5 wt % H incorporated within N–H species identified by Fourier transform infrared spectroscopy. One recent study revealed analogous results for thin films produced by an similar synthesis method, while a previous investigation instead reported formation of crystalline gC3N4 flakes with a triazine-based graphitic carbon nitride (TGCN) structure. The structures of the materials produced here were studied using a combination of high resolution transmission electron microscopy, X-ray diffraction, IR and Raman and X-ray photoelectron spectroscopy, along with series of density functional theory (DFT) calculations carried out for a range of model layered structures. The results indicate the graphitic layered gC x N y materials contain a mixture of sp2-hybridized C–N and C–C bonded structures, with TGCN to graphene-like domains existing within the layers. Paramagnetic centers localized on the C3N3 rings revealed by electron paramagnetic resonance spectroscopy correspond to potential defect structures within the graphitic layers predicted by DFT calculations. Our results combined with those of previous researchers indicate that a range of graphitic carbon nitride materials could exist with different C/N/H ratios leading to tunable electronic properties for catalysis, semiconducting, spintronics and energy applications, that could be targeted by controlling the synthesis and thin film deposition procedures.

Abiotic degradation of s‐triazine pesticides analyzed by surface‐enhanced Raman scattering

“…The formation of polymeric triazine compounds was also reported in recent years by Komatsu et al in catalytic reactions leading to graphite‐like carbon nitride compounds . Vibrational spectra [Fourier‐transform infrared spectroscopy (FTIR) and (Raman)] obtained from these compounds also indicate that similar polymerization process could also occur in the s ‐triazine rings resulting from the degradation of pesticides, such as ammeline, leading to the formation of some coumpound close to carbon nitrides …”

Structure and reactivity of 2,4,6-tricyano-1,3,5-triazine under high-pressure conditions

“…Layered polytriazine imide (PTI) crystals were first obtained through the condensation of melamine (2,4,6-triamino-1,3,5-triazine) and cyanuric chloride (2,4,6-trichloro-1,3,5-triazine) at pressures between 1-4 GPa and temperatures up to 600 • C [16][17][18] . Crystalline polytriazine imide (PTI) phases containing intercalated Li + and Br − or Cl − ions have been produced by condensation reactions from dicyandiamide (DCDA) in a molten salt (LiCl/KCl or LiBr/KBr) flux 19,20 and triazine-based graphitic carbon nitride (TGCN) and related C-rich layered crystals have been found to form following deposition from the vapour or at the melt-vapour interface [21][22][23] . A pillared-layer phase was obtained by further compression of one of these structures, C 6 N 9 H 3 •HCl, resulting in interlayer C-N bonds formed above approximately 40 GPa 24 .…”

“…and macroscopic graphitic phases produced by polymerization of DCDA with C:N ratios reported between 1.2 to 0.75 21,22 . The spectrum differs significantly from other heptazine-and triazine-based polymeric structures that typically contain strong features due to N-H stretching vibrations 42 .…”

“…Raman signature contains two broad features between 1000-2000 cm −1 that resemble the D and G bands of layered carbon and carbon nitride materials 22,42,43 . The intensity of the "D" band is nearly twice that of the "G" feature, that has been associated with clustering at higher N content in graphitic carbon nitride samples 44 .…”

Prediction of a Stable Organic Metal-Free Porous Material as a Catalyst for Water-Splitting

“…The conduction band minimum (CBM) is situated on K point and the valence band maximum (VBM) is situated on M point, which shows that g-C8N6 is an indirect band-gap semiconductor. Many similar carbon nitride structures have been synthesized [37][38][39], so perhaps a carbon-rich g-C 8 N 6 layered structure may exhibit sufficient stability to be synthesized in future. We checked the stability of the structure theoretically through two methods.…”