17June 2023 ESRFnews

CATALYSIS

CHEMISTRY without catalysis, would be a sword without a handle, a light without brilliance, a bell without sound, said the German chemist Alwin Mittasch. He was not wrong. Today, catalysis empowers many of our most important industrial reactions, not least the Haber process for the production of ammonia, the iron catalyst of which Mittasch was instrumental in identifying in the early 20th century.

Iron may not be in particularly short supply, but many other catalysts are  platinum, for instance, which is employed in the Ostwald process for the production of nitric acid, or in vehicle exhaust for reducing harmful gases, or in fuel cells to promote the splitting and recombination of hydrogen. With a cost of over 32,000 per kilo, platinum is not a metal you want to use liberally, and it is no surprise that industry turns to

nanoparticle forms, which, with their very high surface- area-to-volume ratio, are believed to offer the best return on investment. However, according to Marie-Ingrid Richard, a physicist based at CEA Grenoble who has been a visiting scientist at the ESRF s ID01 beamline for over a decade, it is becoming increasingly well-known that the atomic surface-structure is very different at the nano-scale to the bulk. To know how to make nano particle catalysts work best, we need to know how atoms are actually adsorbed onto a single nanoparticle catalyst, she says.

This is easier said than done. Obviously, catalytic nanoparticles are very small, invisible to the naked eye; they are also unstable, liable to shift this way or that at the slightest disturbance. Past studies have only been able to determine average properties over billions of particles, or particles in unrealistic working conditions, or both.

Nanotechnology is widely used in industrial catalysis, but observing the behaviour of single catalytic nanoparticles has been highly challenging. The EBS is changing that.

The single life

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Marie-Ingrid Richard s team sets up an experiment at the ID01 beamline.