Study: Solar-to-hydrogen efficiency of >9% in photocatalytic water splitting (DOI: 10.1038/s41586-022-05399-1)
A new kind of solar panel, developed at the University of Michigan, has achieved 9% efficiency in converting water into hydrogen and oxygen—mimicking a crucial step in natural photosynthesis. Outdoors, it represents a major leap in the technology, nearly 10 times more efficient than solar water-splitting experiments of its kind.
But the biggest benefit is driving down the cost of sustainable hydrogen. This is enabled by shrinking the semiconductor, typically the most expensive part of the device. The team’s self-healing semiconductor withstands concentrated light equivalent to 160 suns.
Peng Zhou uses a large lens to concentrate sunlight onto the water-splitting catalyst. Outdoors, the device was ten times more efficient than previous efforts at solar water splitting. Image credit: Brenda Ahearn/Michigan Engineering, Communications and Marketing
Currently, humans produce hydrogen from the fossil fuel methane, using a great deal of fossil energy in the process. However, plants harvest hydrogen atoms from water using sunlight. As humanity tries to reduce its carbon emissions, hydrogen is attractive as both a standalone fuel and as a component in sustainable fuels made with recycled carbon dioxide. Likewise, it is needed for many chemical processes, producing fertilizers for instance.
“In the end, we believe that artificial photosynthesis devices will be much more efficient than natural photosynthesis, which will provide a path toward carbon neutrality,” said Zetian Mi, U-M professor of electrical and computer engineering who led the study reported in Nature.
A close-up of the panel with the semiconductor catalyst and water inside. Bubbles of hydrogen and oxygen travel up the slope to be separated in the canister (maybe). Photo: Brenda Ahearn/Michigan Engineering, Communications and MarketingA close-up of the panel with the semiconductor catalyst and water inside. Bubbles of hydrogen and oxygen travel up the slope to be separated in the canister (maybe). Image credit: Brenda Ahearn/Michigan Engineering, Communications and Marketing
The outstanding result comes from two advances. The first is the ability to concentrate the sunlight without destroying the semiconductor that harnesses the light.
“We reduced the size of the semiconductor by more than 100 times compared to some semiconductors only working at low light intensity,” said Peng Zhou, U-M research fellow in electrical and computer engineering and first author of the study. “Hydrogen produced by our technology could be very cheap.”
And the second is using both the higher energy part of the solar spectrum to split water and the lower part of the spectrum to provide heat that encourages the reaction. The magic is enabled by a semiconductor catalyst that improves itself with use, resisting the degradation that such catalysts usually experience when they harness sunlight to drive chemical reactions.
Ishtiaque Ahmed Navid, a doctoral student in electrical and computer engineering, operates the molecular beam epitaxy device in which he grew the semiconductor that harnesses …….