New catalyst is 10 times more efficient than previous solar-powered water separators

Cheap, sustainable hydrogen through solar energy

Peng Zhou uses a large lens to focus sunlight on a water-splitting catalyst. Outdoors, the device is ten times more efficient than previous solar water separation efforts. Credit: Brenda Ahearn/Michigan Engineering, Communications and Marketing

A new type of solar panel, developed at the University of Michigan, has achieved 9% efficiency in converting water to hydrogen and oxygen—mimicking a key step in natural photosynthesis. Outdoors, it represents a huge leap in technology, almost 10 times more efficient than solar water splitting experiments of its kind.

But the biggest benefit is sustainable cost reduction hydrogen. This is enabled by shrinking the semiconductor, which is usually the most expensive part of the device. The group’s self-healing semiconductor withstands as much concentrated light as 160 suns.

Currently, humans produce hydrogen from fossil fuel methane, using a lot of fossil energy in the process. However, the harvested tree hydrogen atom from water using sunlight. When humanity tries to reduce carbon emissions, hydrogen is attractive both as a stand-alone fuel and as an ingredient in sustainable fuels made from recycled carbon dioxide. Likewise, it is necessary for many chemical processfertilizer production, for example.

“Ultimately, we believe that artificial photosynthesis devices will be much more efficient than natural photosynthesis, which will provide a pathway towards carbon neutrality,” said Zetian Mi, professor of electrical engineering. and UM computers, said the study’s lead author. Nature.

Outstanding results come from two strides. The first is the ability to focus sunlight without destroying the light-harvesting semiconductor.

“We have reduced the size of the semiconductor more than 100 times compared to some semiconductors that only operate at low light intensities,” said Peng Zhou, UM researcher in electrical and computer engineering and author of the study. said the first author of the study. “The hydrogen produced by our technology can be very cheap.”

And the second way is to use both the higher energetic part of the solar spectrum to split the water and the lower part of the spectrum to provide the heat that encourages the reaction. Magic activated by a semiconductor catalyst self-improvement with use, against the degradation such catalysts typically experience when they harness sunlight to drive chemical reactions.

In addition to handling high light intensity, it can thrive at high temperatures that are harmful to computer semiconductors. The higher temperature accelerates water splitting, and the extra heat also encourages the hydrogen and oxygen to remain separate rather than renewing their bond and forming water again. Both of these helped the team capture more hydrogen.

For the outdoor experiment, Zhou set up a lens the size of a house window to focus sunlight onto an experimental panel just a few inches across. In that panel, the semiconductor catalyst is covered in a layer of water, bubbling up hydrogen and oxygen gas from which it separates.

Cheap, sustainable hydrogen through solar energy

Close-up of a panel with a semiconductor catalyst and water inside. The hydrogen and oxygen bubbles move uphill to be separated in the box (probably). Credit: Brenda Ahearn/Michigan Engineering, Communications and Marketing

The catalyst is made of indium gallium nitride nanostructures, grown on a silicon surface. That semiconductor wafer captures light, turns it into free electrons and holes—the positively charged voids left when electrons are released by light. The nanostructures are covered by nano-sized metal balls, 1/2000 millimeter in diameter, that use those electrons and holes to help direct the reaction.

A simple layer of insulation on the top of the panel keeps the temperature at 75 degrees Celsius, or 167 degrees Fahrenheit, warm enough to help encourage response while also cool enough for Semiconductors catalyst to perform well. The outdoor version of the experiment, with less reliable sunlight and temperature, is 6.1% efficient at converting energy from the sun into hydrogen fuel. Indoors, however, the system is 9% efficient.

The next challenges the team plans to tackle are to further improve efficiency and achieve ultra-high purity hydrogen that can be fed directly into a fuel cell.

Some of the intellectual property associated with this work has been licensed to NS Nanotech Inc. and NX Fuels Inc., co-founded by Mi.

More information:
Zetian Mi, Solar to hydrogen efficiency more than 9% in photocatalytic water splitting, Nature (2023). DOI: 10.1038/s41586-022-05399-1.

quote: Cheap, sustainable hydrogen: New catalyst 10 times more efficient than previous solar-powered water separators (2023, 4 Jan) retrieved Jan 4, 2023 from https :// -hydro-catalyst-efficiency.html

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