Researchers at the Rice University in the US have developed a technology that captures sunlight to convert it into renewable energy by splitting water molecules.


The technology uses light-activated gold nanoparticles to harvest sunlight and transfer solar energy to highly excited electrons, which are referred to as ‘hot electrons’.

Though they have the potential to drive very useful chemical reactions, the hot electrons decay at a fast pace.

Thus, the solar energy providers must capture the high-energy electrons before they cool in order to increase their solar-to-electric power-conversion efficiencies.

A team of researchers including Isabell Thomann, Hossein Robatjazi, Shah Mohammad Bahauddin and Chloe Doiron have developed a system that uses energy liberated by hot electrons to split molecules of water into oxygen and hydrogen which are feedstocks for fuel cells, electrochemical devices that produce clean electricity.

In order to use hot electrons, the researchers first discovered a way to separate hot electrons from their corresponding low energy stated electron holes.

They have developed a three layer system comprising a thin sheet of shiny aluminum at the bottom which is covered with a thin coating of transparent nickel-oxide, and scattered atop this is a collection of plasmonic gold nanoparticles.

The plasmonic gold nanoparticles are in the form of puck-shaped disks with a diameter ranging from 10 to 30 nanometers.

When the sunlight hits the discs either directly or as a reflection from the aluminum, the light energy is converted into hot electrons.

The resulting electron holes will be attracted by aluminum, while the nickel oxide allows them to pass while acting as a barrier to the hot electrons, which stay on gold.

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

Thomann said: "Utilizing 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.

"We are confident that we can optimize our system to significantly improve upon the results we have already seen."

Image: Rice University researchers have demonstrated a new way to capture the energy from sunlight and convert it into renewable energy by splitting water molecules. Photo: courtesy of Rice University News & Media.