As carbon nanotubes (CNTs) inevitably contain defects, an understanding of their effect on the electrochemical behavior is crucial. We consider, through Cyclic Voltammetry and Raman Spectroscopy, the influence of both intrinsic and extrinsically introduced defects. Bamboo and hollow multi-walled carbon nanotube morphologies provided examples of the former while the controlled addition of Argon and Hydrogen ions was used for studying extrinsic defects. We show that the electrocatalytic response of the hollow type CNTs can be tailored significantly, while bamboo type CNTs have innately high reactive site densities and are less amenable to modification. Argon irradiation also differs greatly from that of Hydrogen irradiation. CNT irradiation with Argon appears to positively charge CNTs, while Hydrogen irradiation neutralizes defects further allowing for the tuning of CNT defect density. The work has implications in the design of nanotube and nanowire based chemical sensors.