News articles

Two Conductors of a Chemical Reaction: Effect of promoter atoms

For the first time, researchers at TU Wien have successfully observed the operating principle of so-called promoters in a catalytic reaction in real-time. These promoters play an important role in technology, but so far there is only limited understanding of how they work.

RH Nanoparticles

Promoters are important in catalysis, but the atomistic details of their function and particularly their role in reaction instabilities such as kinetic phase transitions and oscillations are often unknown. Employing hydrogen oxidation as probe reaction, a Rh nanotip for mimicking a single Rh nanoparticle and field electron microscopy for in situ monitoring, a La-mediated local catalytic effect was demonstrated. The oscillatory mode of the reaction provides a tool for studying the interplay between different types of reaction pacemakers, i.e., specific local surface atomic configurations that initiate kinetic transitions. On the pure Rh nanoparticle, two pacemakers induce a complex oscillatory pattern, alike music from an orchestra with two conductors. The presence of La shifts the bistable reaction states, changes the oscillation pattern and deactivates one of two pacemaker types for the La-free surface. With only one conductor, the music gets slower and more ordered. The observed effects originate from the La-enhanced oxygen activation on the catalyst. The experimental observations were corroborated by micro-kinetic model simulations comprising a system of 25 coupled oscillators.

l.t.r.: Günther Rupprechter, Carla Weigl, Johannes Zeininger, Maximilian Raab, Alexander Genest (top), Yuri Suchorski (bottom).