Unconventional syntheses of nanomaterials for applications in energy conversion and storage

Abstract

Efficient and durable energy conversion and storage devices, such as fuel cells or lithium ion batteries, are essential to increase the use of alternative, clean sources of energy and decrease societies' dependence on fossil fuels. However, current technologies for energy conversion and storage need to be greatly improved to allow for cost efficient energy alternatives. Nanomaterials are important for many applications, including noble metals for catalysis, Group 14 metals for batteries, and metal oxides for light conversion. Their syntheses can be classified into two approaches: bottom-up (condensing molecular species) and top-down (miniaturizing bulk materials). However, these strategies have many disadvantages including scalability due to strict precursor identities and experimental conditions, and the production of high-quality nanoparticles (NPs) with limited size and shape control. This thesis demonstrates two simple, scalable, effective, and unconventional methods for synthesizing nanomaterials for applications in heterogeneous catalysis, rechargeable batteries, and photovoltaics. The two methods combine the advantages of top-down and bottom-up strategies: 1) alternating voltage induced electrochemical synthesis (AVIES) of colloidal metal and metal oxide NPs, and 2) ball milling assisted surface protection (BMASP) for the synthesis of colloidal lithiated Group 14 NPs. These methods are successful in producing high-quality metal and metal oxide NPs. The AVIES method is simple, versatile, cost-effective, and environmentally benign. It is capable of producing a wide variety of NPs with excellent catalytic activity. The BMASP method is specially designed for synthesizing colloidal lithiated Group 14 (Si, Ge, and Sn) NPs in an easy and safe manner. It has provided deeper insights into lithiated anodes and helped to begin to solve the poor cyclability problem that results from the huge volume fluctuations that is preventing commercialization.