Warmer temperatures are finally upon us here on the East Coast, prompting many of us to get outside into the sunlight and play. To Bruce Parkinsonand colleagues at theUniversity of Wyoming, the sun is more than just a welcome sight after a long winter. It could someday provide a real, sustainable alternative to fossil fuels.
The finite supplies of fossil fuels, such as coal and gas, are being depleted. And burning them produces the main greenhouse gas carbon dioxide. Alternative ways to generate energy haven’t really caught on yet, though. They can be costly, and in their current forms, they can’t make enough energy to replace even a fraction of the fossil fuels. Many researchers are working on improving solar panels, but even though their efficiencies have improved and their costs have decreased, they can’t produce power when the sun goes down.
Enter Parkinson’s team. They and others are placing their bets on a different way of harvesting and storing energy from the sun. They are working on devices that “split” water (H2O) to get hydrogen (H2) and oxygen (O2). The hydrogen would be used as fuel, which can be stored and used at night when it’s dark, as well as for powering cars and trucks. To make the dream a reality, the materials in the device must be efficient, inexpensive, earth-abundant and stable for years. But what materials would work?
Parkinson had a thought — a metal oxide semiconductor would fit the bill as a photocatalyst in such a device, especially if the semiconductor were made of a few different metals. But with about 60 metals in the periodic table, the number of combinations he’d have to test was mind-boggling.
After his grad student Mike Woodhouse put together an initial ink-jet printer-based protocol to produce and analyze various metal combinations, Parkinson realized that he had a lot of work ahead of him. He remembers thinking that he’d either have to start a company, hire a bunch of engineers to automate the process or outsource the problem. Because the idea seemed simple, outsourcing seemed like the best option.
And that’s how theSHArK(Solar Hydrogen Activity Research Kit) project started in 2006. The kits include materials, such as an apparatus based on a Lego Mindstorm® kit, an electrochemical cell, a green laser pointer, an electronics box and fluorine-doped tin oxide plates. The students use the kits to prepare metal oxide films and test them for water-splitting activity.
“We started with undergrads, but enthusiastic high school teachers have taken it to high schools for AP Chemistry classes and science projects,” says Parkinson. He and colleagues have now sent more than 70 kits to high school and undergraduate students around the world.
In a recent issue of ACS Applied Materials & Interfaces, Parkinson’s team reports that an undergrad named Thanh D. Do, then at Gonzaga University, happened upon a potential winning combination — a semiconducting p-type oxide containing iron, aluminum and chromium. Do is also a co-author on the paper. John Rowley, a postdoc in the Parkinson lab, using more sophisticated research tools, followed up on his discovery and found that it has many promising properties, such as a high photovoltage. Parkinson says his team and other researchers will continue to improve the material to enhance the photocurrent response.