Morphology controlled synthesis of 1-D-nanomaterials for electrocatalysis and energy storage applications
This dissertation is about morphology controlled synthesis of one dimensional (1D) nanomaterials (NMs) for electrocatalysis and supercapacitance applications. Template assisted electrodeposition technique was employed to grow 1D NMs; the morphology of which could be varied from nanotubes (NTs) to nanorods (NRs), through two simple and cost effective methods. In the first method, morphology was controlled by controlling the time of electrodeposition inside the anodic aluminum oxide (AAO) template. The presence of sputtered gold on the inside walls of the template provided the first nucleation sites for the formation of nanotube walls that are subsequently thickened due to gradual increase of the deposition time. We tuned the wall thickness of gold (Au), platinum (Pt) and palladium (Pd) NTs until the formation of nanorods. This method was also extended to synthesize bimetallic and trimetallic NTs. Furthermore, Pt NTs modified with monolayers of tin (Sn) and ruthenium (Ru) were also synthesized through underpotential deposition of Sn and Ru. In the second method, 1D NTs of nickel (Ni) were grown inside the template and were subsequently oxidized to yield 1D-NiO nanostructures; the morphology of which was controlled from nanotube to nanorods due to advancing oxide layer via adjusting the annealing time. The synthesized NSs were tested as electrodes for direct liquid fuel cells and electrochemical supercapacitors. Pt and Pd were characterized for electrooxidation of methanol and formic acid, respectively, while NiO was tested for supercapacitance applications. All our NMs exhibited high electrochemical activity towards electrocatalysis and supercapacitance properties. In addition, modified Pt NTs showed enhanced electrooxidation of methanol as compared to bare Pt. Furthermore, a strong dependence of the electrochemical properties on morphology was observed where, superior electrochemical properties were observed for NTs owing to the large active surface area involved.