On May 11th, a group of international researchers, led by Bert Weckhuysen from Utrecht University and Sara Bals from the University of Antwerp, published a study in Science showcasing a novel method for enhancing the activity and selectivity of a promising CO2-clearing catalyst. The team utilized advanced visualization techniques to precisely illustrate the underlying mechanism of their modified pretreatment approach. First authors Matteo Monai, Kellie Jenkinson, and Angela Melcherts contributed significantly to the research.
The need for cleaning up or repurposing carbon dioxide is becoming increasingly vital, especially in sectors like energy and transportation that generate vast amounts of the greenhouse gas. Catalysts play a crucial role in facilitating efficient and effective cleanup processes. For instance, in CO2 hydrogenation, a commonly used chemical reaction to purify CO2, a nickel-supported titanium dioxide catalyst is employed.
In their research, the team found that the temperature at which the catalyst was prepared had a significant impact on its performance. They observed that the catalyst displayed better selectivity and activity during CO2 hydrogenation when it was prepared at a temperature of 600°C compared to 400°C. This is a desirable outcome since higher selectivity translates to fewer unwanted by-products, while improved activity leads to a more rapid progression of the catalytic reaction. The researchers anticipate that the same principle would apply to catalysts that incorporate metal oxides other than titanium dioxide.
Using advanced electron microscopy techniques, the team was able to visualize this principle with unprecedented accuracy, at the atomic level. They inserted a specialized nanoreactor into the microscope, which facilitated the catalytic process and enabled the researchers to observe precisely what was occurring with the catalyst.
Bert Weckhuysen, one of the lead researchers on the project, explained that during the CO2 hydrogenation process, they observed titanium atoms moving onto the nickel layers and then detaching from them. When the catalyst was subjected to high pretreatment temperatures, some titanium atoms remained attached to the nickel, whereas the layers of titanium completely vanished at lower temperatures.
The concept of strong metal support interaction (SMSI), which involves two chemical elements such as nickel and titanium interacting and forming a catalyst, is not new. However, this study is the first to demonstrate what occurs at the atomic level during this interaction. The movement of titanium layers was never previously witnessed, but the advanced electron microscopy techniques utilized in this study made it possible. Weckhuysen added that their technique allowed them to visualize the process with exceptional resolution, and even count the number of titanium atoms on the nickel.
The international research team that conducted the study had a broad range of expertise, which was critical in achieving the outcomes. Sara Bals explained that they used electron microscopy methods that are typically challenging to combine with nanoreactor experiments. Researchers with diverse backgrounds and access to advanced techniques contributed pieces of a larger puzzle, which ultimately resulted in a complete picture.
Source: Utrecht University