Join the dots for better catalysts

Single metal atoms can be used to prepare more effective catalysts when they are first anchored to nanoparticles of carbon called quantum dots. The new catalysts were developed by an international team with members in the US, Canada, China, and at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia.

Metal atoms can display extraordinary catalytic activity for a wide range of reactions when they are supported on a matrix of graphene, a form of carbon composed of sheets of hexagonal rings of bonded carbon atoms. But such catalysts have low metal atom densities, with typically less than one metal for every 99 carbon atoms.

The new method attaches an array of chemical linkage groups to carbon quantum dots, with each group able to bind to a single metal atom. Extreme heating of this material then produces graphene loaded with almost four times as many metal atoms as the conventional catalysts.

The team demonstrated the new procedure’s potential with a nickel-loaded catalyst that achieved significantly more effective conversion of carbon dioxide into carbon monoxide. This industrially useful reaction is just one initial example.

Many other reactions catalysed by a variety of metal atoms should also benefit from the technique. The researchers have already explored this versatility by using iridium atoms as the metallic catalytic centres.

“This result clearly demonstrates the advantage of high single-atom loadings in improving single-atom catalysis,” the authors say.

They now plan to push the level of metal loading “to the limit”. They will also explore adjustments to the structure of the quantum dots to improve the performance of their catalysts in a variety of applications.

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