Researchers in Switzerland have successfully measured the coordination environments of platinum atoms within single-atom catalysts using platinum NMR spectroscopy. This advancement reveals how the activity of these catalysts is linked to the way atoms bind to their substrates, potentially paving the way for more effective catalyst designs.

Single-atom catalysts typically consist of a metal, frequently enough a precious one like platinum, dispersed on a support material such as nitrogen-functionalized carbon. The active sites are located where the metal and support meet. while microscopy can show how well a metal is spread across a catalyst surface, Javier Pérez-Ramírez at ETH Zürich notes that this isn’t enough. He explains, ‘The techniques that exist provide an average, but single atoms are not single sites … the coordination environments – the local structures – might be very different.’

In a collaborative effort, researchers from the groups of Pérez-Ramírez and Christophe Copéret at ETH Zürich, along with colleagues in France and Denmark, used solid-state platinum-195 NMR spectroscopy on single-atom catalysts. These catalysts featured platinum on nitrogen-functionalized carbon supports. Although NMR doesn’t offer high spatial resolution due to its use of long-wavelength microwave radiation, the chemical shift of the platinum-195 atoms, which depends on their binding to the support, could be analyzed theoretically. Copéret illustrates this by saying, ‘Imagine you’re at the opera and every singer is singing together: we have to listen to all the individual voices and tell what the distribution of the voices is.’

The study demonstrated that different methods of creating the same catalyst could lead to significantly different coordination environments, even if the catalysts appeared identical under a microscope. This could explain why it’s frequently enough difficult to produce consistently active single-atom catalysts. The researchers also investigated how different supports affect the coordination of the catalyst sites. Furthermore, they examined a single-atom platinum catalyst used for the hydrochlorination of acetylene and observed changes after several hours of use, during