Back in 1998, when gasoline prices were $1.03 per gallon, John Turner of the U.S. Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL) dropped jaws all over the energy world by demonstrating that he could use sunlight to extract hydrogen from water at a remarkable 12.4% efficiency.
Three hundred articles and news reports followed, there were predictions of the next big thing, and then … almost nothing happened.
Energy companies went back to their gasoline and their diesel, or their attempts to extract fuel from biofuels, or to extract hydrogen via algae or coal-powered electricity.
Now, with gasoline at $3.89 per gallon, and still the dominant transportation fuel, there is renewed interest in Turner’s work.
Earlier this year, the Japan Society of Coordination Chemistry awarded Turner with its first Lectureship Award for his pioneering work in the fields of solar hydrogen and fuel cells and for being an international spokesman for hydrogen production via photoelectrochemical water splitting. “It was quite an honor to be recognized that way,” he said.
“It’s what I’ve been doing for 30 years, pushing this technology into new areas that are more fruitful,” Turner added. “People are looking at climate change, looking at solar fuels. The tsunami has people in Japan rethinking nuclear, plus they import 90% of their oil. Countries are looking at technologies that give them greater energy independence.”
Momentum Grows for Solar-Fueled Water Splitting
As often happens in science, researchers are turning back to a breakthrough that had lost momentum.
Japan, South Korea, and Singapore are starting advanced artificial photosynthesis centers. This month, DOE announced the availability of $1 million in grants to evaluate technology pathways for cost-competitive hydrogen fuel.
In 2010, DOE established the Joint Center for Artificial Photosynthesis at the California Institute of Technology (Caltech) as one of its Energy Innovation Hubs, with the aim to find a cost-effective method to produce fuels using only sunlight, water, and carbon dioxide as inputs.
It’s photosynthesis without the green stuff. Turner uses multijunction solar cells made mostly from elements in the third and fifth columns of the periodic table, such as gallium, arsenic, and indium. These so-called III-V solar cells still work the best.
NREL also funds research through its Laboratory Directed Research and Development Program aimed at trying to make alloys that combine the benefits of the III-V elements with the strengths of elements such as cobalt, manganese, phosphorous, or titanium. The trick is to combine the materials in such a way that they are not only stable and robust but also have the right band gaps to generate enough voltage to split water.
Turner, who has been with NREL since 1979, says the cleanest way to produce hydrogen is by using sunlight to directly split water into hydrogen and oxygen.
The amount of greenhouse gases such a method can save is almost unfathomable. Consider that in the United States alone, 9 million tons of hydrogen are made each year, much of it in petroleum refineries and primarily via a process called steam reforming of natural gas.
For each kilogram of hydrogen produced that way, about 12 kilograms of carbon dioxide are produced. A process that could replace all that natural gas reforming with the sun and water can save 100,000 trillion kilograms of carbon dioxide from reaching the atmosphere each year. Hydrogen produced from water and sunlight can replace natural gas reforming if it is made near the refinery and used in place of the hydrogen typically made from reforming.
It won’t be easy. In fact, Turner says that the reason his initial breakthrough lost momentum is that improving the technique “was hard work, and people don’t like to do hard work.”
Better technology, the cost of gasoline, and worries about nuclear power in the post-tsunami era have combined to make researchers believe water splitting may be worth the hard work. Turner’s pioneering work — and the renewed enthusiasm for it — is leading researchers in several directions.