Research led by members of the California NanoSystems Institute (CNSI) at UCLA has determined the 3D atomic coordinates, chemical makeup and surface composition of heterogenous nanocatalysts — sized on the scale of billionths of a meter — used in chemical reactions driven by electricity, according to a
news release from UCLA’s chemistry and biochemistry department.
The technique could have a significant impact on the fundamental understanding of catalysts’ active sites and enable engineers to rationally design nanocatalysts in a way that optimizes their performance compared with current methods that are closer to 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, a professor of physics and astronomy at the UCLA College; Yu Huang, the Traugott and Dorothea Frederking Endowed Professor and the chair of the materials science and engineering department at the UCLA Samueli School of Engineering; and Philippe Sautet, a distinguished professor of chemical and biomolecular engineering and the vice chair for graduate education at UCLA Samueli.
Using advances they developed for a microscopy technique called atomic electron tomography, the team studied 11 nanoparticles consisting of either a platinum-nickel alloy alone or that alloy plus traces of molybdenum, another metal that can serve as a catalyst.
The researchers were able to measure a host of characteristics at atomic resolution, including the nanoparticles’ facets, their surface indentations and the relative orderliness of the catalysts’ structures and chemical components.
The data from atomic electron tomography were plugged into artificial intelligence models trained based on fundamental principles of physics and chemistry. With the algorithms, the investigators identified the active sites where catalysis takes place. Those findings were then validated with real-world measurements.
The scientists’ observations revealed that chemical activity at the surface platinum sites varies widely — by several orders of magnitude. The team conducted a comprehensive analysis of the relationship between the nanocatalysts’ structure and chemical activity at the level of individual atoms to formulate an equation providing quantitative insights into the nanocatalysts’ active sites.
Although this study focused on platinum-based alloy nanocatalysts in a specific electrochemical reaction, the general method can be applied with a wide range of nanocatalysts for various reactions to determine the local 3D positions of atoms, as well as the catalysts’ elemental makeup and surface composition.
