The Raman spectrum of a sample (biomass derived carbon material) shows two sharp peaks at about 1340 cm-1 and 1580 cm−1, assigned to D-band and G-band, and two broad peaks at about 2100 cm-1 and 2700 cm-1 respectively.
1) What does these two broad peaks at 2100 cm-1 and 2700 cm-1 indicate? And what is their contribution to supercapacitance value.
According to literature, While G-band is characteristic of graphite, D-band is attributed to defects, curved graphite sheets and lattice distortions in the carbon structures. Degree of graphitisation in CNS-SS was found to be 1.044 and CNS was 1.17.
2) what can I interpret from the ratios?
I have attached the spectrum for kind perusal.
I got this graph from Thermofischer DSR Raman microscope equipped with a 780 nm laser
It may be due to the low efficiency of CCD (Si chip working up to the gap). 2100 cm-1 with 830 nm excitation is 1005 nm and 2700 cm-1 is 1069 nm.
Therefore, if there is no ICS correction applied to spectra, it might be
instrumental artifacts. If you repeat in with different wavelength, it will be more clear what may be the origin. It is possible to have some peaks between 2500-2900 cm-1 which are double or mixture of main peaks.
at ~2700 there should be normally the 2D band of graphene/graphite. Its an overtone of 2D. But in your high defective material is should be really broad and less intense. Also, D+G combination mode should be present little higher, but difficult to deconvolute here.
You tried to graphitize biomass, right? Somehow, there seems to be a lot of organic random orgnic residues. At high wavenumbers, there should be additional modes reaching from many different CH-vibrations (~2800 +) ...
Try to find a table for vibrational Raman modes similar to IR. Maybe you can find out by comparing with your initial material, what it contained and what it should contain after all reactions occured for the peak at 2100.
Thank you Sergey Mamedov : I will try measurement with different instrument to check for the instrument artifacts.
@ Christian Halbig : Yes, i graphitized biomass, followed by acid wash to remove the organic content. I will look for a table for Raman vibrational modes.
Thank you both for your valuable inputs.
The following papers have a detailed discussion on Raman analysis of
carbon materials.
https://www.sciencedirect.com/science/article/pii/S0254058419303256
http://www.ipme.ru/e-journals/RAMS/no_14115/04_14115_ali.html