Microstructural analysis of nitrogen-doped char by Raman spectroscopy: Raman shift analysis from first principles

Abstract

Nitrogen-doped materials are known to possess unique functional properties, making these materials potentially useful for environmental applications, heterogeneous catalysis, and electronics. In this paper we constructed first principles-based models of various polyaromatic structures containing N functionalities to better understand the effect of these functional groups on char Raman spectra. The presence of N functional groups induces active vibrations in the regions between 1400 and 1550 cm À1 and 1605-1650 cm À1 . We used these insights to inform the deconvolution of N-doped cellulose char produced between 350 and 700 C using cellulose/melamine blends 2:1. A consistent increase in the intensity of the D and G bands is observed with temperature, which is related to an increase in size of the aromatic cluster. A consistent decrease in the A (the valley region) band is related to the loss of heteroatoms (mainly N and O) as the carbonization temperature increases from 350 to 700 C. Although the modeling results reported in this manuscript are used to inform the deconvolution of N-doped char Raman spectra, they are also relevant to study other nanocarbon-based materials.

Green self-activation engineering of metal–organic framework derived hollow nitrogen-doped carbon spheres towards supercapacitors

“…36–38 The D′ band at ∼1680 cm −1 normally refers to the defect induced peak associated with disorder in graphene. 39,40 Statistically, the degree of graphitization ( i.e. , the height ratio of I D / I G ) of HNCSs-700 (Fig.…”

Single‐Atom Tailored Hierarchical Transition Metal Oxide Nanocages for Efficient Lithium Storage

“…Further, the absence of Nb 2 O 5 Raman signal in the case of 3DH‐Co 3 O 4 @Nb samples illustrates that Nb is successfully riveted into Co 3 O 4 , thus leading to all the peaks shifted toward high wavenumber range (Figure S6a, Supporting Information, more detail can be seen in Supporting Information). [ 16 ] According to the crystallographic feature of XRD patterns (Figure S6b, Supporting Information), all the diffraction peaks for three samples can be well assigned to the cubic Co 3 O 4 crystal. [ 17 ] For the 3DH‐Co 3 O 4 @Nb, the diffraction peaks shift to low degree after doping Nb atom (Figure S6c, Supporting Information), which can be explained via Bragg equation in Equation S13 (Supporting Information).…”

The Thermo-Oxidative Behavior of Cotton Coated with an Intumescent Flame Retardant Glycine-Derived Polyamidoamine: A Multi-Technique Study

“…In both COT and COT/M-GLY, the position of the G peak and the ratio of the intensities I(D)/I(G) > 0.5 are indicative of the formation of nanographitic structures. Comparing the two histograms that report the area ratio for D and G peaks in Figure 7c,d, it is possible to observe that the amount of D and G areas are comparable at 300 • C and 350 • C. Conversely, at 420 • C in COT/M-GLY the large D bandwidth, together with the small shift observed by increasing temperature, suggests the presence of condensed aromatic structures of different sizes (Figure 7b), whose formation is obviously induced by M-GLY [17,18]. 13 C SSNMR spectra were recorded on residues of COT and COT/M-GLY after heating in air at 300 °C, 350 °C, and 420 °C using the 1 H-13 C cross-polarization (CP) technique.…”

“…Comparing the two histograms that report the area ratio for D and G peaks in Figure 7c,d, it is possible to observe that the amount of D and G areas are comparable at 300 °C and 350 °C. Conversely, at 420 °C in COT/M-GLY the large D bandwidth, together with the small shift observed by increasing temperature, suggests the presence of condensed aromatic structures of different sizes (Figure 7b), whose formation is obviously induced by M-GLY [17,18]. The Raman spectra of COT and COT/M-GLY are shown in Figure 7a,b.…”