Scientists discover why silver nanoparticles on carbon are 200 times more effective than their pure equivalents.

Precious metals like silver, platinum, and palladium have acted as essential industry catalysts, their properties enabling unique chemical reactions quickly and efficiently. When in nanoparticle form and supported by a carbon base, the catalytic properties of these precious metals increase dramatically without science knowing why – until now.

Researchers at TU Wien, the Vienna University of Technology in Austria, can finally explain the interaction between nanoparticles and carbon substrates which has been mysteriously improving their effectiveness.

"For a long time, the use of carbon as a carrier material for catalysis had something almost magical," said Professor Günther Rupprechter from the Institute of Materials Chemistry at TU Wien. "It always seemed a bit like black art."

The scientist chose silver, a promising catalyst for hydrogen fuel cells, to use in its experiments.

Using hydrogen isotope exchange, the research team developed a faster, simpler method for evaluating various carbon catalyst supports for effectiveness, with computer simulations revealing the sweet spot - the zone where the metallic nanoparticles are in direct contact with the carbon.

The origin of carbon samples also turned out to be surprisingly important.

Carbon can be derived from coconut shells, fibers, or special woods. Different carbon production methods were proven to lead to measurable variances.

The larger the area of direct contact between silver particles and carbon carriers, the greater the activity crucial to maximum efficiency. The catalyst effect was demonstrably greatest where the two materials met.

"So, it's not the size of the carbon surface or any foreign atoms or functional groups. An extreme catalytic effect occurs when a reactant molecule comes into contact with both a carbon and a silver atom directly at the interface," said Alexander Genest, who ran computer simulations comparing the activation of hydrogen by silver nanoparticles on carbon and compared them to simulations using pure silver.

"In the chemical industry, people are naturally often content with the fact that a process works and can be repeated reliably," said Rupprechter. "But we wanted to get to the origin of the effect and understand exactly what is actually going on here at the atomic level."

The team supplied two samples – silver nanoparticles on a carbon substrate and a pure silver foil. Both samples were examined in a chemical reactor, with astonishing results.

"For each silver atom, the carbon background induces a two hundred times higher activity," said Thomas Wicht, lead author of the resulting published study. "This is of course very important for industrial applications. You only need a two-hundredth of the amount of expensive precious metals to achieve the same activity – and you can do that simply by adding comparatively inexpensive carbon."

"Now that we have understood the mechanism of action, we know exactly what to pay attention to," added Rupprechter.

This discovery and form of testing carbon substrate allows for analysis of carbon batches from different sources at the atomic level for ideal effectiveness, a fine-tuning of catalyst manufacture and the potential halving of precious metals used in the industry.