Science, Space and Technology News 2024
Scientists have shown that platinum atoms on cerium oxide can assemble into active nanocatalysts under reaction conditions and then disassemble when cooled down before reuse. Credit: Valerie Lentz/Brookhaven National Laboratory
“Part of the definition of a catalyst is that it helps disassemble and reassemble reacting molecules to form new products,” Frenkel noted. “But it was shocking to see a catalyst that also assembles and disassembles itself in the process.
“Carbon monoxide molecules have a very strong repulsive interaction when they are next to each other,” Frenkel explained. During the “reverse water gas shift” reaction, which converts carbon dioxide at high temperatures, the CO typically leaves the catalyst surface as a gas. But once the heat is turned off, the CO molecules bind strongly to the platinum atoms of the catalyst. This brings the CO molecules closer to each other as the system cools down and their numbers rise.
“It can’t tell us whether all platinum atoms have the same environment or whether we have different groups of atoms — some dispersed on the support and some within the nanoparticles. We needed additional tools to unravel the possibilities,” he said. “These techniques together tell us that, once the reaction stops and the temperature drops, the nanoparticles have started to fragment into single atoms,” Frenkel said. “Each measurement independently would not have given us enough data to understand what we are dealing with. We couldn’t have done this work without our collaborators at NSLS-II and CFN and without the capabilities at these DOE Office of Science user facilities.
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