Unlocking the Secrets of Catalysts: How Tiny Traces Revolutionize Chemical Reactions

Unveiling the Mysteries of Catalysts: How Minute Traces Revolutionize Chemical Reactions

A groundbreaking achievement at TU Wien has transformed our comprehension of catalyst promoters by providing direct insights into the role of lanthanum atoms in enhancing rhodium nanoparticle catalysts. This study illuminates the profound influence of these promoters on crucial facets of the catalyst, profoundly impacting the chemical reaction process. Illustrated below is an image depicting water molecules and the nanoparticle, courtesy of TU Wien.

For the first time ever, researchers at TU Wien have achieved a significant breakthrough by observing the functioning of promoters in catalytic reactions in real-time. Promoters hold a pivotal position in technology, yet their mechanisms have remained shrouded in mystery until now.

Catalysts are indispensable in numerous chemical applications, from purifying exhaust emissions to producing valuable chemicals and energy carriers. Frequently, minuscule quantities of additional substances, known as “promoters,” are introduced to catalysts to augment their efficacy. Despite their crucial role in technology, promoters have posed a formidable challenge to study.

Traditionally, determining the specific effects of different promoter quantities on a catalyst has involved a trial-and-error approach. However, researchers at TU Wien have achieved a breakthrough by directly observing the impact of lanthanum promoters on hydrogen oxidation. Leveraging advanced microscopy techniques, they have visualized the actions of individual lanthanum atoms.

Their investigation has unveiled that two specific regions of the catalyst serve as pacemakers, akin to conductors directing an orchestra. The promoter assumes a pivotal role in governing the actions of these pacemakers. The outcomes of this research have been published in the prestigious journal Nature Communications.

Live Observation of Reactions

Prof. Günther Rupprechter from the Institute of Materials Chemistry at TU Wien remarks, “Many chemical processes employ catalysts in the form of minuscule nanoparticles.” While assessing catalyst performance through product analysis is straightforward, gaining microscopic insights has hitherto been an elusive endeavor.

This situation has now been transformed. Over several years, Günther Rupprechter and his team have developed sophisticated methodologies that allow the direct observation of individual nanoparticles during chemical reactions. This breakthrough enables us to witness how activity fluctuates at distinct locations on these nanoparticles throughout the course of the reaction.

Rupprechter explains, “We employ rhodium nanotips that function as nanoparticles. They can act as catalysts, such as when hydrogen and oxygen combine to form water molecules, which is the specific reaction under scrutiny.”

Oscillation Between “Active” and “Inactive”

In recent years, the TU Wien team demonstrated that different regions of nanoparticle surfaces exhibit varying behaviors, oscillating between an active and an inactive state. Sometimes, the desired chemical reaction transpires at specific locales, while at other times, it remains dormant.

Dedicated microscopes have revealed that multiple such oscillations occur concurrently on each nanoparticle and exert mutual influence. Certain regions of the nanoparticle surface, often just a few atomic diameters wide, assume a more significant role than others, functioning as highly efficient “pacemakers” that orchestrate the chemical oscillations of other regions.

Promoters can now intervene in this pacemaker behavior, thanks to the methodologies pioneered at TU Wien. When rhodium serves as the catalyst, lanthanum can act as a promoter for catalytic reactions. Individual lanthanum atoms were meticulously positioned on the tiny surface of a rhodium nanoparticle. By comparing the particle’s behavior in the presence and absence of the promoter, this approach has meticulously revealed the specific effects of individual lanthanum atoms on the progression of the chemical reaction.

Lanthanum Alters the Equation

Maximilian Raab, Johannes Zeininger, and Carla Weigl conducted these experiments. Maximilian Raab emphasizes, “The disparity is significant. A lanthanum atom can bind to oxygen, altering the dynamics of the catalytic reaction.” Even a minuscule amount of lanthanum reshapes the interplay between various regions of the nanoparticle.

Johannes Zeininger elaborates, “Lanthanum can selectively deactivate certain pacemakers. Visualize an orchestra with two conductors – complex music would result. The promoter ensures there is only one pacemaker left, simplifying and harmonizing the situation.”

In addition to the experimental measurements, the team, with support from Alexander Genest and Yuri Suchorski, devised a mathematical model to simulate the interplay between the individual areas of the nanoparticle. This approach represents a more comprehensive method to describe chemical catalysis, moving beyond mere input and output to embrace a complex model that accounts for how different catalyst regions alternate between activity and inactivity, all under the guidance of promoters, influencing each other in a harmonious symphony.

Reference: “Lanthanum modulated reaction pacemakers on a single catalytic nanoparticle” by Maximilian Raab, Johannes Zeininger, Yuri Suchorski, Alexander Genest, Carla Weigl, and Günther Rupprechter, published on November 8, 2023, in Nature Communications. DOI: 10.1038/s41467-023-43026-3

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