Ultrasonic synthesis of materials for energy conversion devices

There is no doubt about the fact that the development of improved energy conversion and storage devices is the biggest issue in the 21st century. A variety of mobile electronics are on the market more than ever, and battery-powered electrical vehicles are no longer a dream. However, the energy conversion and storage devices are the bottleneck in technological innovation, since the materials which applied to these devices have not shifted a lot from the early 20th century; therefore, it is now essential that new economic and ecological technologies are found to synthesize better performing materials. Nanostructured materials for a better energy conversion and storage have been a topic of interest because unique mechanical, electrical, and optical properties of materials have been observed by confining the materials nano-scaled; hence the improvement in performance of the energy conversion and storage devices. There have been proposed enormous numbers of studies regarding the synthesis routes for nanostructured materials, since materials characteristics depend very much on the applied synthetic routes. In this sense, applying ultrasound to the materials’ synthesis has attracted much attention. Sonochemistry is found to be a very effective way of producing nano-sized materials with unique properties, while ultrasonic spray pyrolysis shows promising results for the mass production of the nanostructured materials. Therefore in this dissertation, synthesis of nanostructured materials by applying ultrasound for the better performing energy conversion and storage devices, specifically supercapacitors, quantum dot sensitized solar cells, and lithium-ion batteries will be discussed in detail. For a supercapacitor application, ultrasonic spray pyrolysis has been applied to synthesize high capacitance carbon materials with high surface area and oxygen-related surface functionality, which are found to be beneficial to improve capacitance. Ultrasonic spray pyrolysis has also been applied to the synthesis of porous zinc oxide microspheres for quantum dot sensitized solar cells because ultrasonic spray pyrolysis is superior in synthesizing porous materials to other conventional synthetic routes. For a lithium-ion battery application, the effects of high intensity ultrasound to the synthesis of silicon nanoparticles have been investigated. During the research, it was found that sonochemical synthesis is capable of synthesizing silicon nanoparticles in much faster rate and the resultant particles outperform other materials synthesized by a conventional reaction rout