Thomas W. Hamann
Research
Inorganic Materials / Electrochemistry
(Research Description PDF)
Hamann Group Research: The Hamann group is engaged in interdisciplinary research to address basic science issues related to new methods, molecules and materials to convert solar energy to electricity and chemical fuels. Of specific interest are regenerative and non-regenerative photoelectrochemical cells, including dyesensitized solar cells and thin-film absorber photoelectrocatalytic systems. In addition, we are interested in the use of ammonia as an energy (hydrogen) carrier and are investigating electrocatalytic nitrogen fixation and ammonia splitting.
Dye Sensitized Solar Cells: Ultra-fast electron injection from a photoexcited sensitizer into a photoanode produces a charge separated state with typically high quantum efficiency. We are primarily interested in the subsequent processes of dye regeneration and recombination which control the efficiency of charge collection. We systematically vary the components involved in each reaction and interrogate them with a series of photoelectrochemical measurements. The general lessons learned will ultimately be used to develop design rules for next generation DSSCs comprised of molecules and materials which can overcome the kinetic and energetic constraints of current generation cells. In addition, we are investigating new related paradigms of solar energy conversion based on the knowledge gained from more conventional systems.
Thin Film Absorber Solar Cells: We are interested in exploring the use of thin film semiconductors to drive photoelectrochemical water splitting (solar fuel-forming) reactions. We are currently elucidating the rate limiting steps as well as water oxidation mechanism on the electrode surface. Additional topics of recent interest include understanding the effect of substrate and underlayer materials, incorporation of dopants, and surface layers (e.g. catalysts) on the water oxidation efficiency. Additional oxide, nitride and oxynitride semiconductor materials are also under current investigation.
Ammonia Electrocatalysis: Nitrogen is the most abundant gas in Earth’s atmosphere and water is the most abundant liquid on Earth’s surface; combining the catalytic reduction of N2 with the oxidation of H2O to produce NH3 offers a route to scalable renewable energy storage. Liquid ammonia has an energy density comparable to methanol, and the stored chemical energy can in principle be used to generate electricity or H2 on demand. The electrolysis of liquid NH3 has received limited attention to date, however. We are also engaged on a broader collaborative effort with the Smith group to investigate the electrocatalytic conversion of liquid NH3 to H2. In addition, we are developing new electrocatalysts based on earth-abundant materials for NH3 synthesis and electrolysis.