Studies of Nanomaterials for Energy Conversion and Storage: Metal Electrocatalysts and Sodium-ion Battery Anodes

The increasing environmental concern and the expedited consumption of fossil fuels make the development of sustainable energy technology more urgent and significant. Nanoscience and technology recently have attracted much attention due to their appealing applications in the fields of clean energy technology. The advancement of the renewable materials shines the light to the alternative energy sources, where fuel cells and batteries are the most noticeable candidates. The goal of this research is to show the relationship between the nano-structures and the electrochemical properties by modified preparation process and provide deeper insight into the mechanisms for fuel cells and batteries application.
As a representative fuel cell, direct methanol fuel cells (DMFCs) have recently gained interest because methanol is energy-dense and reasonably stable at all environmental conditions. One of the key reactions of DMFCs, methanol oxidation reaction (MOR), is kinetically sluggish. Here we developed tunable pore size Au micromeshes with a high density of surface as an effectively active electrocatalyst for MOR. The electrochemical performance of Au micromeshes can be further tuned experimentally, based on the d-band theory. There are other important electrochemical reactions that require high performance catalysts. For example, electrochemical carbon dioxide reduction reaction (CO2RR) is a promising way to store energy from intermittent electricity sources and simultaneously deplete the redundant CO2 in the air. Here I investigated the grain size effect of porous Cu nanowires on the selective electrocatalytic reduction of CO2, demonstrating that grain size engineering is an effective approach to enhance the electrocatalytic performance of metal catalysts. Electrochemical reactions also contribute to energy storage by batteries. This thesis also describes anode materials for sodium-ion batteries (SIB). A major challenge of SIB is lack of a suitable anode with high capacity and long-term cyclability. In this research, Sb2Te3/C nanocomposite has been successfully prepared as anode for SIB. The Sb2Te3 nanocrystals are embedded in the carbon matrix, which not only provides an electron path, but also binds the Sb2Te3 nanograins together and suppresses the pulverization during cycling.