Characterization of Low-Energy Electron-Irradiated Single-Walled Carbon Nanotubes using Raman Spectroscopy and Desorption Analysis

Hydrogen is a key component of renewable energy initiatives, but storage remains a challenge. Graphene can possibly be hydrogenated through electron irradiation, but current research has primarily focused on crystalline flakes, a costly and unscalable form. As such, this study investigates how irradiation affects the defect-activated Raman modes and desorption characteristics in Unpurified HiPCo SWCNT films. Samples were prepared by dispersing SWCNT powder in dimethylformamide (2 mg/mL) and depositing onto SiO2 substrates. One sample was irradiated to 2.55 * 10^15 electrons/square centimeter at 1.5 keV and analyzed through temperature-programmed desorption and sequential Raman spectroscopy, with a non-irradiated sample as a control. Raman deconvolution shows irradiation-driven enhancement of the D-peak and changes within the substructure of the larger G-peak (the latter not observed in purified HiPCo samples), indicating changes in defect chemistry and other interactions possibly involving amorphous carbon and Fe catalyst. Thermal annealing reverses the growth in the D-band, with preliminary results of TPD analysis revealing a rightward shift in the secondary H2 desorption peak for irradiated samples, suggesting altered adsorption environments. Future work will extend this approach to purified and unpurified films exposed to H2O or D2O prior to irradiation, allowing for analysis of how initial physisorbed molecules affect desorption mechanics. Overall, preliminary results demonstrate how combined Raman and desorption spectroscopy provide insight into irradiation and annealing-driven defect formation as well as changes in adsorption dynamics in SWCNT networks, with future work giving more analysis to conditions under which these changes can be modified.