A Chemistry Thesis Defense by Trenton Gallagher (Ji Group)

Sustainable generation of energy is imperative to meet the demands of growing populations. The current state of energy production relies heavily on fossil fuels to power large turbines, generating electricity that can be applied to local power grids. In recent years, however, there has been a major shift to promoting renewable energy production. New technology has arrived that now allows for efficient capture of energy from solar rays and wind. Unfortunately, these energy sources are intermittent, only producing energy when the sun is shining, or the wind is blowing. The necessity for storage of this energy until it is needed during the evenings when people are using most of their energy is very important for these renewable energy sources to be widely adopted. By developing new secondary battery systems, this goal can be achieved.

In this dissertation, the primary objective is to discover more sustainable electrode materials and study new reaction mechanisms using aqueous electrolytes. The first study conducted reveals a reversible conversion reaction from copper to Cu₂CO₃(OH)₂. The reaction mechanism uses OH^- and CO₃^2- as charge carriers at the cathode. The results open an avenue to use carbonate as a charge carrier for batteries to serve for the consumption and storage of CO₂.

In a follow up study on the copper electrode, fluoride was identified as a promising charge carrier for batteries due to its high charge/mass ratio and small radius. Here, commercial copper powder exhibits reversible storage of F^- in a 16 mKF aqueous electrolyte. This electrolyte suppresses dissolution of CuF₂, the charged product. Furthermore, the KF solid comprised in the Cu electrode facilitates a high initial capacity. Our results showcase the potential of aqueous fluoride batteries using copper as an electrode.