Effect of a variety of carbon nanotubes on the iodine–iodide redox pair

The iodide (I−)-triiodide (I3-) redox pair was used as a model system to evaluate the potential catalytic activity of various carbon nanotubes. Aqueous solutions of hydroiodic acid were irradiated with ultraviolet light in the presence of single wall, multi-wall, boron-doped and nitrogen-doped multi-wall carbon nanotubes. The nitrogen-doped multi-wall carbon nanotubes showed significant catalytic activity in the generation of hydrogen triiodide, while the other carbon nanotubes studied inhibited the generation of hydrogen triiodide. The photoconversion of hydroiodic acid to hydrogen triiodide, catalyzed by the nitrogen-doped multi-wall carbon nanotubes, was further accelerated by the presence of dissolved oxygen, offering an additional decomposition pathway for hydroiodic acid.