Throwing light on nanomaterial photocatalysts

Using sunlight to drive chemical reactions such as artificial photosynthesis could soon become much more efficient thanks to nanomaterials, say researchers from Imperial College London in the UK. Their work on such nanomaterials could ultimately help improve solar energy technologies and be used for new applications, such as using sunlight to break down harmful chemicals.

Sunlight is used to drive many chemical processes that would not otherwise occur. For example, carbon dioxide and water do not ordinarily react, but in the process of photosynthesis plants take these two chemicals and, using sunlight, convert them into oxygen and sugar.

The efficiency of this reaction is very high, meaning much of the energy from sunlight is transferred to the chemical reaction, but so far scientists have been unable to mimic this process in man-made artificial devices. One reason for this is that many molecules that can undergo chemical reactions with light do not efficiently absorb the light themselves. They rely on photocatalysts – materials that absorb light efficiently and then pass the energy on to the molecules to drive reactions.

In this new study, which is reported in a paper in Nature Communications, the Imperial researchers, together with colleagues in Germany and the US, investigated an artificial photocatalyst material made from metal nanoparticles and found out how to make it more efficient. This discovery could lead to better solar panels, allowing energy from the sun to be harvested more efficiently. The novel photocatalyst could also be used to destroy liquid or gas pollutants, such as pesticides in water, by harnessing sunlight to drive reactions that break down the chemicals into less harmful forms.

“This finding opens new opportunities for increasing the efficiency of using and storing sunlight in various technologies,” said lead author Emiliano Cortés from the Department of Physics at Imperial. “By using these materials we can revolutionize our current capabilities for storing and using sunlight with important implications in energy conversion, as well as new uses such as destroying pollutant molecules or gases and water cleaning, among others.”

The researchers showed that light-induced chemical reactions occur in certain regions over the surface of these nanomaterials. They also identified which areas of the nanomaterial would be most suitable for transferring energy to chemical reactions, by tracking the locations of very small gold nanoparticles (used as a markers) on the surface of the silver nanocatalytic material.

Now that they know which regions are responsible for the process of harvesting light and transferring it to chemical reactions, the team hope to be able to engineer the nanomaterial to increase these areas and make it more efficient.

“This is a powerful demonstration of how metallic nanostructures, which we have investigated in my group at Imperial for the last 10 years, continue to surprise us in their abilities to control light on the nanoscale,” said lead researcher Stefan Maier. "The new finding uncovered by Dr Cortés and his collaborators in Germany and the US opens up new possibilities for this field in the areas of photocatalysis and nanochemistry.”

This story is adapted from material from Imperial College London, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.