Findings on the production of exsolution catalysts published.
Catalysts made of solid-state materials are used for the production of 90 percent of industrially important chemicals. One important type of such catalysts consists of metallic nanoparticles finely dispersed on an oxide support. There are several critical challenges in the production of catalysts: The metal particles must not be too large or too close together, and they must remain so even under (often extreme) conditions of use so that the often expensive metals are used as efficiently as possible.
Recently, interest in “exsolution” as an uncomplicated way of overcoming these challenges has grown considerably. Exsolution starts from a solid solution containing all the constituents (the metal is dissolved in the oxide carrier) and then exposes the solid solution to certain environmental conditions to force the system to release the metal as finely dispersed nanoparticles on the carrier surface. Until now, however, there has been a lack of fundamental knowledge as to why exactly the exsolution takes place, how it occurs and how quickly it happens.
The Article
Alexander Bonkowski, Dr. Matthew J. Wolf and Professor Roger A. De Souza from the Institute of Physical Chemistry at RWTH Aachen University, together with researchers from Technische Universität Darmstadt and the University of Bath, have now published the article “A Single Model for the Thermodynamics and Kinetics of Metal Exsolution from Perovskite Oxides” in the Journal of the American Chemical Society. They propose a new, fundamental answer to these questions for an important class of oxides, namely perovskites. Using chemical calculations carried out on the high-performance computers at RWTH, the scientists show that the metal ions can be reduced to metal atoms under the environmental conditions prevailing during catalyst production while still inside the carrier material – a possibility that had not been considered before.
This understanding of the exsolution process will facilitate the optimization of catalytic activity and accelerate the development of new exsolution systems.
