15 JUL 2018
Star-shaped gold nanoparticles, coated with a semiconductor, can produce hydrogen from water over four times more efficiently than other methods – and could lead to better ways to store solar energy, a new study shows.
The discovery could also lead to other advances that could boost renewable energy use and fight climate change, researchers say.
“Instead of using ultraviolet light, which is the standard practice, we leveraged the energy of visible and infrared light to excite electrons in gold nanoparticles,” says Laura Fabris, associate professor in the materials science and engineering department at Rutgers University.
“Excited electrons in the metal can be transferred more efficiently into the semiconductor, which catalyzes the reaction.”
The researchers focused on photocatalysis, which typically means harnessing sunlight to make faster or cheaper reactions. Titanium dioxide illuminated by ultraviolet light is often used as a catalyst, but using ultraviolet light is inefficient.
As reported in Chem, the researchers tapped visible and infrared light that allowed gold nanoparticles to absorb it more quickly and then transfer some of the electrons generated as a result of the light absorption to nearby materials like titanium dioxide.
The engineers coated gold nanoparticles with titanium dioxide and exposed the material to UV, visible, and infrared light and studied how electrons jump from gold to the material.
They found that the electrons, which trigger reactions, produced hydrogen from water over four times more efficiently than previous efforts demonstrated. Hydrogen can be used to store solar energy and then combusted for energy when the sun is not shining.
“Our outstanding results were ever so clear,” Fabris says. “We were also able to use very low temperature synthesis to coat these gold particles with crystalline titanium. I think both from the materials perspective and the catalysis perspective, this work was very exciting all along.
“This was our first foray,” she says, “but once we understand the material and how it operates, we can design materials for applications in different fields, such as semiconductors, the solar or chemical industries, or converting carbon dioxide into something we can use. In the future, we could greatly broaden the ways we take advantage of sunlight.”
An additional coauthor of the study is also from Rutgers.