Enhanced Electron Transfer Kinetics of Covalent Carbon Nanotube Junctions

Improving the electrochemical activity of carbon nanotubes (CNTs) requires control over their geometrical and electronic structure. Recently, we have reported a covalently interconnected nanostructure of CNTs (named 3D-CNTs) by the Suzuki C-C coupling reaction, where it is shown to have enhanced heterogeneous catalytic properties. Here, the microscopic electrochemical investigation conducted reveals the structure-property correlation of such a structure. The micro Raman spectroscopic studies reveal the presence of defects at the CNT junction. The heterogeneous electron transfer (HET) rate of 3D-CNTs is quantitatively correlated with the defect generated by the coupling reaction. The improved HET rate of 3D-CNTs is found to be because of the higher density of states at the Fermi level of CNTs, enhancing the overlap between electronic states of CNTs and redox couples. Scanning electrochemical microscopy imaging suggests the enhanced electrochemical activity of the interconnected junctions of the 3D-CNTs, correlating the previously observed bulk catalytic property with their microscopic origin.