University of Minnesota
School of Physics & Astronomy

Spotlight

Alternative energy

Woods Halley
Woods Halley
Jonathan Chapman
                                                       

J. Woods Halley has worked many years on problems associated with alternative energy. Halley applies his knowledge of the physics of electro-chemistry to energy-relevant problems. He has been working with chemists from 3M and Argonne National Laboratory on problems in hydrogen fuel cells proposed for use in cars that would refill at hydrogen stations.

In an energy economy depending on renewable, intermittent sources such as wind and solar energy, hydrogen would serve as a means to store and transport the generated energy. At the point of use, oxidation of hydrogen as a fuel produces no emissions except water.

The Halley group has studied the physics associated with two technical problems which have arisen in fuel cell development. During fuel cell operation, when the electrons are stripped from the hydrogen molecules, and the resulting protons are transported through the device to reach the electrode where they combine with oxygen from the air to form water and generate electrical energy. The proton transport through existing devices causes a dissipation of energy. The dissipation is tolerable as long as temperatures in the fuel cell are low. Device engineers would like to raise the temperature to increase reaction rates, but the proton transport slows down too much. They are studying alternative transport media called ‘ionic liquids’ which have improved proton transport properties at higher temperatures. The transport mechanism was found to have unexpected properties including dependence on the concentration of protons. “We found that at a certain concentration the protons were clustering, though they are of like charge, as if they were on the ragged edge of phase separation” Halley says. The clustering can account for the anomalous behavior and suggests design strategies for optimizing proton transport in fuel cells using ionic liquids as transport media.

Another problem with the hydrogen fuel cell is that the reaction in which protons combine with molecular oxygen to form water, called “oxygen reduction” is anomalously slow. The mechanism of the reaction is still not fully understood, making scientifically guided improvements in performance difficult. The group has developed software that models the surface of the platinum electrodes at which the reaction takes place, making a more comprehensive theoretical study of the process.

The group is also currently studying a proposed method for improvement of the efficiency of conversion of wind generated electricity to hydrogen stored energy with support from the University Center for Urban and Regional Affairs.

More information at http://www.physics.umn.edu/people/woods.html