Electron Spin Resonance Studies of Hydrogen Adsorption on Defect-Induced Carbon Nanotubes

Abstract

Multi-walled carbon nanotubes were subjected to harsh acid treatment for subsequently increasing periods of time. Transmission electron micrographs show that metallic particles are largely removed in this process and that nanofibers are preferentially destroyed. Acid treatment induces defects through segmentation of the tube walls. These changes were studied using electron spin resonance spectroscopy, and the response of the defects to hydrogen adsorption was monitored over a temperature range from ambient to 5 K. The interaction of hydrogen mainly with defects is manifested in the largest increase in signal amplitude for the sample with the most defects and in the increase of the spin lattice relaxation time at temperature below 10 K.