The Meyer group is interested in understanding how to control light induced electron transfer reactions as they apply to electrical power generation and catalysis. Our overall goal is to design molecular-semiconductor interfaces that drive desired electron transfer reactions when illuminated with sunlight.
This requires a detailed knowledge of reaction mechanisms in heterogeneous environments. Our research combines aspects of inorganic chemistry, including synthesis and supramolecular coordination chemistry, with photoelectrochemistry and materials science.
Dye-sensitized semiconductors based on mesoporous thin films of anatase TiO2 nanocrystallites provide a means for conversion of sunlight to electrical power (with efficiencies > 13%) and for water splitting to generate hydrogen gas (with efficiencies approaching 1 %). These materials also offer unprecedented opportunities to understand, and ultimately control, light driven reactivity. Our group has paid particular attention to controlling the unwanted charge recombination of electrons injected into TiO2 with the oxidized dye and/or redox mediator. A recently discovered electro-absorption signature allows quantification of the electric fields present at the interface. The use of conducting oxides has recently provided fundamental insights into the reorganization energies associated with electron and proton coupled electron transfer.
Our group is designing supramolecular complexes based on transition metals that can drive water and/or halide oxidation when illuminated with visible light. We pay particular attention to the excited states that initiate the reaction chemistry and look for opportunities to advance fundamental science with an eye towards practical applications. Supramolecular assemblies exploit non-covalent interactions through hydrogen bonding and electrostatic ion-pairing. Natural population analysis from density functional theory allows the site(s) of ion association to be predicted. Halide oxidation studies have focused mainly on iodide and, to a lesser extent, bromide. Chloride is often used as a non-redox active anion that can be recognized and, under specific conditions, photo-released. In some cases, this photochemistry is extended from fluid solution to semiconductor-electrolyte interfaces where desired behaviors can be exploited in photoelectrochemical cells.
We are interested in electron transfer reactions that occur with strong (adiabatic) and weak (non-adiabatic) electronic coupling. We have recently shown that strong electronic coupling results in more rapid electron transfer, but at the expense of some free energy losses. A particularly interesting non-adiabatic electron transfer reaction is lateral self-exchange intermolecular ‘hole-hopping’ that occurs across solid surfaces. This reaction allows translation of charge without a loss of free energy. While a great deal is known about light driven electron transfer reactions when the electronic coupling is fixed, much less is known about how the coupling influences reactivity when the free energy is fixed. We continue to exploit this fact for advancement of fundamental science with the very real possibility for practical applications in solar energy conversion.