Preparation and Characterization of Chemically Modified Amorphous Carbon Electrodes
Catherine Grace McKenas
Chemically modified materials are an important component of dye-sensitized solar cells. Metal oxides are a common electrode material in dye-sensitized solar cells; the dye molecule that undergoes photon absorption must be attached the metal oxide nanomaterial. While dye molecule attachment can be covalent or non-covalent in nature, covalent linkages offer an advantage due to their greater stability. However, covalent modifications of metal oxide surfaces degrade upon exposure to electrochemical
... cycling, rendering the chemistry inefficient for use in solar cells where long-term stability is needed. Amorphous carbon is an attractive alternative material to replace metal oxide film electrodes due to its semi-conducting nature and ability to be readily chemically modified. In this work, I developed four new strategies to modify amorphous carbon films, including approaches compatible with: thiol-ene click reactions, azide-alkyne click reactions, and direct surface attachment with an in situ Grignard reaction. These surface modifications were fully characterized with: x-ray and ultraviolet photoelectron spectroscopies, scanning electron and atomic force microscopies, water contact angle measurements, and cyclic voltammetry. The analysis of these covalent modifications revealed low coverages and formation of disordered monolayers. The monolayers formed by many of the covalent modification strategies for metal oxides are disordered in nature; this makes the electron transfer through these monolayers more complex than traditionally accepted models of electron transfer for self-assembled monolayers on gold. These modified amorphous carbon films make a great test-bed to understand electron transfer through disordered films; therefore, the electron transfer through these films was analyzed. Overall, this work outlines new chemistries on amorphous carbon as well as offers a new perspective on understanding electron transfer through disordered films.