Stephen DeWitt

Harvesting and Storing the Sun’s Energy

By Stacy Kish on August 4, 2010

Helping a group build medical devices for developing countries, Stephen DeWitt began to understand that one of the critical problems facing these regions is lack of reliable power. Solar energy may be the key.

DeWitt, a doctoral pre-candidate at the University of Michigan and a DOE Office of Science Graduate Fellow, has been interested in physics since the second grade. The summer before beginning graduate school he worked on a project using a photoelectrochemical cell to generate hydrogen. And the pieces fell into place.

“I am looking into nanoscale materials to generate hydrogen directly from sunlight,” explains DeWitt. “Energy storage is always the biggest problem with solar energy,” he said. “Batteries are expensive, but the hydrogen approach that I am working on is relatively stable, will keep indefinitely, and can generate clean electricity with the only byproduct being water.”

To accomplish this task, DeWitt writes computer simulations to try to understand how perfectly ordered nanotube structures occur in metal oxides. “This is important, explains DeWitt, “because when light enters a nanotube, the excited electron (negative charge) produces a hole (positive charge).” The electron completes the circuit and the hole must make it to a water solution where it can collect hydrogen. “The problem is that most holes cannot span the hundreds of nanometers in the metal oxide to make it to the water solution,” he explains. The nanotube structure allows the holes to go just a few nanometers to the side of the tube to reach the water solution (instead of having to go straight back upward).  This process is crucial for producing hydrogen directly from solar radiation.

DeWitt credits the graduate fellowship with giving him the flexibility to explore all options in his research. “I can follow my own path and begin collaborations with other non-traditional energy scientists.” DeWitt’s graduate fellowship is funded by the American Recovery and Reinvestment Act of 2009.

Stacy Kish is a Science Writer with the Office of Science