Gold standard for catalysts

An international team of researchers has discovered how the inert metal gold becomes a highly active catalyst when reduced to nanoparticles.

Gold nanoparticles can transform carbon monoxide into carbon dioxide, remove odours and toxins and help clean automotive exhaust gases. The researchers from Switzerland, UK, the USA and the ESRF (European Synchrotron Radiation Facility) in Grenoble have monitored the catalytic process and proposed an explanation for the high catalytic activity of gold, which is published in Angewandte Chemie.

Scientists already knew that gold nanoparticles react with this kind of setup and catalyse carbon monoxide with oxygen to create carbon dioxide. What they did not know was how the oxygen is activated on the catalyst. In order to find that out, they set up a cell where they could carry out the reaction, and monitored it in situ using X-ray absorption spectroscopy.

The researchers first applied a flow of oxygen over a layer of gold nanoparticles and observed how the oxygen becomes chemically active when bound on them. While constantly monitoring the samples, they switched to a flow of carbon monoxide and found that the oxygen bound to the gold reacted with the carbon monoxide to form carbon dioxide. Without the gold nanoparticles, this reaction does not take place.

“We knew beforehand that the small gold particles were active, but not how they did the reaction. The nice thing is that we have been able to observe, for the first time, the steps and path of the reaction. The results followed almost perfectly our original hypotheses. Isn’t it beautiful that the most inert bulk metal is so reactive when finely dispersed?” said Jeroen van Bokhoven, one author of the paper.

The possible applications of this research could involve pollution control such as air cleaning, or purification of hydrogen streams used for fuel cells. The technique used could also be used to study other catalytic systems, with the aim of improving their performance and making them more stable.