rice solar team

Researchers at the Rice University in Houston, Texas, US, have developed an innovative technology that captures energy from sunlight and enables it to be converted into green energy by splitting water molecules.

The technology is based on a configuration of light-activated gold nanoparticles that transfers this energy into highly excited electrons or ‘hot electrons’, and then captures them to generate power.

As well as allowing solar manufacturers to increase the efficiency of their solar-to-electric power-conversion, this technology can also support US initiatives to lower solar power costs.

Details about the invention have been published in the American Chemical Society journal Nano Letters.

Rice University assistant professor and lead researcher for the project Isabell Thomann said: "Hot electrons have the potential to drive very useful chemical reactions, but they decay very rapidly, and people have struggled to harness their energy.

"For example, most of the energy losses in today’s best photovoltaic solar panels are the result of hot electrons that cool within a few trillionths of a second and release their energy as wasted heat."

Thomann and her team have created a system that extracts the energy from hot electrons and uses it ‘to split molecules of water into oxygen and hydrogen.’

These gases then function as a feedstock for the fuel cells, which work as electrochemical devices to generate power.

"Hot electrons have the potential to drive very useful chemical reactions, but they decay very rapidly, and people have struggled to harness their energy."

The technology set-up by the researchers features three layers of materials. A bottom layer of a thin sheet of shiny aluminum covered with a thin coating of transparent nickel-oxide. Above that, there is a scattered collection of plasmonic gold nanoparticles; puck-shaped disks about ten to 30 nanometers in diameter.

Sunlight enters the discs either directly or after being reflected by the aluminium.

Rice University said: "The aluminum attracts the resulting electron holes and the nickel oxide allows these to pass while also acting as an impervious barrier to the hot electrons, which stay on gold.

"By laying the sheet of material flat and covering it with water, the researchers allowed the gold nanoparticles to act as catalysts for water splitting.

"In the current round of experiments, the researchers measured the photocurrent available for water splitting rather than directly measuring the evolved hydrogen and oxygen gases produced by splitting, but Thomann said the results warrant further study."

"Utilising hot electron solar water-splitting technologies, we measured photocurrent efficiencies that were on-par with considerably more complicated structures that also use more expensive components," Thomann added.

The researchers intend to conduct further research in order to improve the technology and the system efficiency.

Image: Rice University researchers (clockwise from left) Chloe Doiron, Hossein Robatjazi, Shah Mohammad Bahauddin and Isabell Thomann. Photo: courtesy of Rice University News and Media.