Structural Investigation of Graphitic Carbon Nitride via XRD and Neutron Diffraction

Abstract

Graphitic carbon nitride (g-C 3 N 4 ) has, since 2009, attracted great attention for its activity as a visible light-active photocatalyst for hydrogen evolution. Since it was synthesized in 1834, g-C 3 N 4 has been extensively studied both catalytically and structurally. While its 2D structure seems to have been solved, its 3D crystal structure has not yet been confirmed. This study attempts to solve the 3D structure of graphitic carbon nitride by mean of x-ray diffraction and of neutron scattering. Initially, various structural models are considered and their XRD patterns compared to the measured one. After selecting possible candidates as g-C 3 N 4 structure, neutron scattering is employed to identify the best model that describes the 3D structure of graphitic carbon nitride. Parallel chains of tri-s-triazine units organized in layers with an A-B stacking motif are found to describe the structure of the synthesized graphitic carbon nitride well. A misalignment of the layers is favorable because of the decreased π-π repulsive inter-layer interactions.

Shining Light on Carbon Nitrides: Leveraging Temperature To Understand Optical Gap Variations

“…The asprepared PCN sample often has a C/N ratio of around 0.67, and ∼1 wt% H. Therefore, the structure of this carbon nitride is best represented by the melon model. [15][16][17][18][19] . This model has compositional formula C 6 N 9 H 3 .…”

“…1a contains the XRD patterns of samples prepared at temperatures from 500 to 700 • C. These samples show characteristic patterns of melon. 15,17,18 Two main reflections at ∼ 13 • and ∼ 27.5 • are assigned to intralayer periodicity (210) and interlayer periodicity (001), respectively. Transmission Electron Microscopy (TEM) images show that CN700 has a plate-like morphology ( Fig.…”

Carbon nitrides: synthesis and characterization of a new class of functional materials

“…22,[49][50][51] This synthesis procedure results in polymeric materials that have a limiting composition near that of Liebig's melon, with structures derived from ribbon-like elements formed by linked chains of heptazine (C 6 N 7 ) units. [20][21][22]49,50,52 Among the amorphous materials produced at higher temperatures, some elements containing more highly condensed graphite-like domains may be present, but this has not been proved experimentally. It might be expected that the end result from continued elimination of NH 3 would cause formation of fully graphitic g-C 3 N 4 layers based on linked polyheptazine units (Fig.…”

Reexamination of Solvothermal Synthesis of Layered Carbon Nitride

“…Since hep002 / tri002 decreased with heating duration (Figure 5(c)), the layered structure is considered to consist mainly of s-triazine-based network. However, a first-principle calculation [3] reported that heptazine-based carbon nitride is thermodynamically more stable than the s-triazine-based one, and some experimental studies also showed the production of the heptazinebased carbon nitride under high temperatures [13,42,44,45]. Thomas et al [43] reported that the condensation of striazine ring unit to heptazine ring unit occurred at above 390 ∘ C through the elimination of ammonia.…”