Inorganic Materials / Electrochemistry

Thomas Hamann

Associate Professor

411 CEM

517-353-1072


Research webpage


Primary Research Area

Inorganic (In)

Other Area(s) of Interest

Material (Ma)

Physical (Ph)

Research

Hamann Group Research: There is a LOT of energy from sunlight striking the Earth’s surface: approximately 1017 Joules/second. For comparison, the averaged worldwide energy demand is approximately 1013 Joules/second. The Hamann group is engaged in interdisciplinary research to address basic science issues related to new methods and materials for utilizing this incredible resource to produce electricity and chemical fuels. Of specific interest are regenerative and non-regenerative photoelectrochemical cells, including dye-sensitized solar cells and thin-film absorber photocatalytic systems. In addition, we are interested in the use of ammonia as an energy (hydrogen) carrier and are investigating the electrocatalytic synthesis and electrolysis of ammonia.

Dye Sensitized Solar Cells: We are investigating the fundamental role of the relevant dye-sensitized solar cell, DSSC, components (redox shuttle, photoanode and sensitizer) involved in key efficiency-determining processes. 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 are capable of overcoming the kinetic and energetic constraints of current generation cells.

Thin Film Absorber Solar Cells: We are interested in exploring the use of thin films to overcome the problems associated with short collection length materials. One absorbing material of current interest is α-Fe2O3 (hematite). Hematite is an attractive material for solar energy conversion due to the abundance of iron in the earth’s crust, the extremely low cost, chemical stability and environmental harmlessness. In addition, hematite has been shown to be a promising water oxidation photocatalyst in a fuel-forming (non-regenerative) photoelectrochemical cells. 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 therefore exploring the electrocatalytic conversion of liquid NH3 to H2. We are also engaged on a broader collaborative effort to develop and investigate new electro-catalysts based on earth-abundant materials for NH3 synthesis and electrolysis.


 

Selected Publications

Hajibabaei, H., Zandi, O., Hamann, T.W.; “Tantalum Nitride Films Integrated with Transparent Conductive Oxide Substrates via Atomic Layer Deposition for Photoelectrochemical Water Splitting” Chemical Science2016, 7, 6760

Zandi, O., Hamann, T.W.; “Determination of Photoelectrochemical Water Oxidation Intermediates on a-Fe2O3 Electrode Surfaces Employing Operando ATR–IR Spectroscopy” Nature Chemistry, 8, 778–783 (2016)

Xie, Y., Baillargeon, J., Hamann, T.W.; “Regeneration and Recombination Reactions in Dye Sensitized Solar Cells Employing Cobalt Redox Shuttles” Journal of Physical Chemistry C., 2015, 119 (50), 28155 – 28166

Little, D.J., Smith, M.R., Hamann, T.W.; “Electrolysis of Liquid Ammonia for Hydrogen Generation” Energy & Environmental Science2015, 8, 2775 – 2781

Ondersma, J.W.; Hamann, T.W.; “Conduction Band Energy Determination by Variable Temperature Spectroelectrochemistry.” Energy and Environmental Science 2012, 5 (11), 9476 – 9480

Klahr, B.M., Gimenez S., Fabregat-Santiago, F., Bisquert, J., Hamann, T.W.; “Photoelectrochemical and Impedance Spectroscopic Investigation of Water Oxidation with “Co-Pi” coated Hematite Electrodes.” Journal of the American Chemical Society 2012, 134 (40), 16693 – 16700

Ondersma, J.W.; Hamann, T.W.; “Measurements and Modeling of Recombination from Nanoparticle TiO2 Electrodes.” Journal of the American Chemical Society 2011, 133, 8264 – 8271

CV

B.A., 1996, Univ. of Texas

M.S., 2000, Univ. of Massachusetts

Ph.D., 2006, California Institute of Technology

Postdoctoral Fellow, Northwestern Univ. 2006-2008

Awards/Honors

2015 Kavli Fellow
2015 SEAC Royce W. Murray Young Investigator Award
2013 Camille Dreyfus Teacher-Scholar Award
2012 Alfred P. Sloan Research Fellowship
2012 National Science Foundation, CAREER award
2011 Department of Energy, Early Career Research Program award