Insights into the role of defects on the Raman spectroscopy of carbon nanotube and biomass-derived carbon

Raman spectroscopy can effectively detect disorder in carbon materials through defect-activated peaks. However, distinguishing between different defect species in carbon using Raman spectroscopy is often challenging, leading to potentially misleading attributions, particularly in the case of carbon materials containing a significant number of amorphous components. In this study, we provide a comprehensive analysis of in-situ Raman spectra from commercially available carbon nanotubes (CNTs) with various defects during its annealing treatment process. Through the in-situ removal of different oxygen functional groups and H atoms during annealing treatment of CNTs, we track and discuss dynamic surface changes to unveil their impact on the Raman spectra. Furthermore, we examine the complex influence of amorphous components using biomass-derived carbon as a model for amorphous carbon, shedding light on their contributions to Raman spectra. We also consider Raman signals stemming from molecular vibrations in the same spectral regions. By thoroughly understanding the fundamental effects of different types of defects on the two specific carbon models, we try to give some inspirations for analyzing different carbon materials by Raman spectroscopy with high reliability and validity.