Atomic-Scale Details of Catalyst Sites Revealed

The chemical and energy industries rely on catalysts to facilitate the reactions used to produce their products. Many important processes use heterogeneous catalysts – meaning that the catalysts are in a different state than their reactants, such as solid platinum reacting with gases in an electrical appliance. of the car.

Scientists have probed the surface of a well-defined single crystal, illuminating the processes caused by many chemical reactions. However, there is much to learn. For different catalysts, their 3D atomic structure, their chemical structure and the nature of their active sites, where the reaction takes place, have always been difficult.

Now, research led by members of the California NanoSystems Institute at UCLA has determined the 3D atomic coordinates, chemical makeup and surface composition of heterogeneous nanocatalysts – billions of meters in size – used in chemical reactions. electrically powered chemicals.

The group’s approach can significantly impact the fundamental understanding of the active sites of catalysts and help engineers design nanocatalysts in a way that improves their performance, while current methods are more trial and error.

The study, which appeared on the cover of the July issue of Nature Catalysis, was led by corresponding authors and CNSI members Jianwei “John” Miao, professor of physics and astronomy at UCLA College; Yu Huang, Traugott and Dorothea Frederking Professor and chair of the department of materials science and engineering at the UCLA Samuel School of Engineering; and Philippe Sautet, distinguished professor of chemical and biomolecular engineering and associate chair of graduate studies at UCLA Samuele.

Using an advance they developed for a microscopy technique called atomic electron tomography, the team studied 11 nanoparticles containing either a platinum-nickel alloy alone or that combination with traces of molybdenum, an iron one that might help. The researchers were able to measure many properties at atomic resolution, including the nanoparticles’ size, their surface indentation, and the relative arrangement of the catalyst’s structures and chemical components.

Data from atomic electron tomography were fed into artificial intelligence models trained on the principles of physics and chemistry. Through algorithms, the researchers identified the active sites where catalysis takes place. Those findings were then verified with real-world measurements.

Scientists’ observations have revealed that chemical activity in the platinum environment varies greatly – by several orders of magnitude. The team performed a comprehensive analysis of the relationship between nanocatalysts’ structure and chemical activity at the level of individual atoms to create an equation that provides more information on the active sites of nanocatalysts.

Although this study focused on platinum-based nanocatalysts for a specific electrochemical reaction, the general method can be used with many types of nanocatalysts for different reactions to determine the level of What are the 3D atoms, as well as the basic compositions of catalysts and surfaces. composition.

The first authors of the study are Yao Yang of Westlake University in China and Jihan Zhou of UCLA, Zipeng Zhao and Geng Sun. The other authors are Saman Moniri, Yongsoo Yang, Ziyang Wei, Yakun Yuan and Yang Liu, all of UCLA; Colin Ophus, Jim Ciston and Peter Ercius of Lawrence Berkeley National Laboratory’s Molecular Foundry; Cheng Zhu and Hendrik Heinz of the University of Colorado at Boulder; and Qiang Sun and Qingying Jia of Northeastern University.