TU Wien scientists uncover complexities of catalysts

Tiny metal particle catalysts play a crucial role in various technological applications, ranging from fuel cells to the production of synthetic fuels for energy storage. However, understanding the intricate details and interactions that govern catalyst behavior can be challenging. Even when preparing two catalysts with identical compositions, they can exhibit minute differences, leading to distinct chemical behaviors.

At TU Wien, scientists are actively investigating the factors behind such effects by employing multiple microscopy techniques to observe catalytic reactions occurring at different locations on catalysts. This approach enables them to gain a precise, microscopic understanding of catalytic processes.

Interestingly, this research has revealed that even seemingly “simple” catalytic systems are more complex than initially anticipated. The catalytic properties are not solely determined by the size of the metal particles or the chemical nature of the supporting material. Within a single metal particle, various scenarios can coexist on the micrometer scale. By combining experimental observations with numerical simulations, researchers have been able to explain and accurately predict the behavior of different catalysts.

Not all particles are the same

Professor Günther Rupprechter, from the Institute of Materials Chemistry at TU Wien, explains their research focus on studying the combustion of hydrogen and oxygen using rhodium particles as catalysts, which ultimately results in the production of pure water. In this process, several parameters play a crucial role. These include the size of the individual rhodium particles, the support material they bind to, as well as the temperature and reactant pressures during the reaction.

However, Professor Rupprechter emphasizes that the catalyst, comprised of supported rhodium particles, does not exhibit uniform behavior that can be adequately described by a few simple parameters, as previously attempted. It quickly became evident that the catalytic behavior varies significantly across different locations on the catalyst. For instance, a specific area on a rhodium particle may display catalytic activity, while another area just a few micrometers away may be catalytically inactive. Moreover, the situation can even reverse within a few minutes.

Nine catalysts at one sweep

Dr. Philipp Winkler, the lead author of the study published in ACS Catalysis, conducted experiments using a remarkable catalyst sample. This sample consisted of nine distinct catalysts, each comprising metal particles of varying sizes and different support materials. To enable comprehensive comparisons, a specialized apparatus allowed all the catalysts to be observed simultaneously in a single experiment.

Winkler highlights the capabilities of their microscopy techniques, which provide detailed information about the catalytic activity, chemical composition, and electronic properties of each individual spot on the catalyst sample. In contrast, traditional methods typically provide average values for the entire sample. However, as demonstrated in the study, such average measurements often fall short in capturing the complexities of catalyst behavior.

The use of advanced microscopy techniques allows for a more precise understanding of catalyst performance by examining each specific location within the catalyst sample. This approach unveils the heterogeneity and diverse characteristics present, providing valuable insights that traditional methods cannot offer.

Even more complex than anticipated

The meticulous chemical analysis conducted on the microscopic scale has revealed an even greater degree of local variation in catalyst composition than anticipated. Surprisingly, within individual metal particles, significant differences were observed. Professor Rupprechter explains that atoms from the support material can migrate onto or into the particles, or even form surface alloys. As a consequence, a clear boundary between the catalyst particle and the support material is often absent, giving way to a continuous transition. Importantly, this intermingling of materials has a profound impact on the chemical activity of the catalyst.

Building upon these findings, the team at TU Wien aims to utilize their newfound insights and successful methodologies to tackle even more complex catalytic processes. Their ongoing mission involves unraveling microscopic-scale processes, contributing to the advancement of improved catalysts, and exploring new catalyst materials.

By deepening our understanding of the intricate behavior occurring at the microscopic level, researchers at TU Wien strive to make significant strides in the development of highly efficient catalysts. These efforts have the potential to revolutionize various industries by enabling more sustainable and efficient chemical processes.

Source: Vienna University of Technology

Leave a Comment