Electron Microscopy Investigations of Surface-modulated Nanomaterials for Electrocatalytic Applications

Abstract

With advancement and increasing usage of technologies, the demand for energy is also growing. However, the limited and ever-depleting stock of natural gas and fossil fuels has necessitated for better solutions in energy generation, conversion, and storage. To address the upcoming energy crisis, research on alternative energy conversion and storage applications has become an active field of interest. One of the most explored fields among them is electrocatalytic energy conversion reactions involving nanomaterials, which are interesting owing to their high activity originating from increased surface to volume ratio compared to the bulk counterpart. In recent literature, electrocatalysis has been employed for a variety of reactions like alcohol oxidation and water splitting. The activity of any catalyst depends on the surface /sub-surface atomic configuration, their electronic structure, and adsorption/ desorption energy of intermediates. Changing the composition of surface and sub-surface leads to change the adsorption and desorption energy of the intermediates on surface. The activity of any catalyst is tuned by surface modifications as and whenever required and their surface modifications lead to improvement in the corresponding property. Noble metal catalysts are well known in literature and were explored for different types of electrocatalysis. In this thesis, nanomaterial-based catalysts based on ultrathin Au nanowires as a template, are explored and their activities were investigated after their surface modifications. Extensive electron microscopic investigations were carried out using scanning transmission electron microscopy as a tool to understand the surface and sub-surface structure and composition at atomic scale. In some scenarios, high-angle annular dark field (HAADF)-STEM imaging can be limited by close atomic numbers of the constituent elements. There, other complementary techniques like XPS have been used to understand the composition. The synthesized templated catalysts have been tested for various reactions like electrocatalytic alcohol oxidations and water splitting reactions.