Stanford researcher William Chueh has developed a novel way to use sunlight to convert water into hydrogen, or water and carbon dioxide into methane, as an alternative method for converting solar heat into useful energy.
Chueh’s breakthrough relies on a discovery he made while a Caltech PhD candidate. He showed that solar heat can turn cerium oxide into an effective catalyst for splitting water to yield hydrogen fuel. Unlike most other hydrogen extraction processes which rely on rare and precious metals like platinum to act as catalysts, cerium oxide is relatively inexpensive.
Chueh uses mirrors to concentrate sunlight 1,500-fold to heat the cerium oxide to 1,500 °C to drive out its oxygen. Steam is fed to the cooling, oxygen-starved cerium oxide which reacts with the oxygen in the water vapor. The freed hydrogen gas is funneled to be stored as fuel. The cerium oxide is then reheated to generate more hydrogen.
Chueh also uses a variation of the technique to split carbon dioxide into oxygen and carbon monoxide. The carbon monoxide can be combined with hydrogen to make hydrocarbon fuels like methane. Remarkably, Chueh’s process can generate about 100 times more carbon monoxide than other processes with a given amount of energy.
The main hurdle to commercializing Chueh’s solar hydrogen still is the expensive alloys needed to hold material at 1,500 ºC. Chueh is developing a promising solution by combining cerium oxide with another material to lower the operating temperature of his hydrogen still to 500 ºC, a range that can be handled by stainless steel vessels.
At Stanford Chueh is expanding on his earlier work by exploring new materials that will enable the use of both the photovoltaic effect and heat to generate fuel. By combining the two approaches, Chueh hopes to achieve even greater efficiency in converting solar energy into fuel.
Chueh, 28, was recently recognized by Technology Review as one of the world’s top 35 innovators under the age of 35 for his hydrogen still.
Chueh joined Stanford’s Materials Science and Engineering department in June of 2012. He earned his PhD in materials science from Caltech in 2010 and his BS in Applied Physics from Caltech in 2005.
Chueh is a Center Fellow at Stanford’s Precourt Institute of Energy. He has been a Distinguished Truman Fellow at Sandia National Laboratories. His many honors include the Caltech Demetriades-Tsafka-Kokkalis Prize in Energy in 2012, the Josephine de Karman Fellowship in 2009, and the American Ceramics Society Diamond Award in 2008.