‘Dumbbell’ atomic pairs tackle decades-old ethanol chemistry problem for everyday products

From perfumes and synthetic flavorings to plastics and resins, acetaldehyde is a chemical used to make countless everyday products. However, producing it efficiently has remained a challenge because the catalysts that convert ethanol into acetaldehyde gradually lose activity, generate unwanted byproducts, or break down over time. Now, researchers have developed a three-metal catalyst that tackles those long-standing problems in an unusual way. By pairing platinum and chromium atoms inside a silver matrix, they created tiny dumbbell structures known as heterometallic pair sites. These atomic pairs selectively remove only the hydrogen atoms needed to convert ethanol into acetaldehyde while suppressing the deactivation pathways seen in comparable platinum-silver and chromium-silver catalysts. “Our catalyst solves an important problem in chemistry because it completes a selective dehydrogenation: Instead of stripping away all of the hydrogen atoms, it removes just the ones necessary,” Anatoly Frenkel, one of the study authors and a chemist at Stony Brook University, said. Moreover, since the process starts with ethanol that can be produced from biomass such as crop residues, forestry waste, and food waste, it could also provide a more sustainable alternative to conventional petrochemical production. Breaking the limits of conventional catalysts Catalysts speed up chemical reactions without being consumed, but making one that is both fast and selective is difficult. In ethanol dehydrogenation, conventional catalysts often keep reacting after removing the required hydrogen atoms, triggering unwanted reactions. Over time, they can also become coated with carbon deposits, known as coking, or undergo structural changes that reduce their performance. To overcome these problems, the researchers turned to quantum mechanical calculations, which predicted that platinum and chromium atoms would naturally pair up when dispersed inside silver. “Prior quantum chemical calculations and surface science experiments by our collaborators showed that platinum-chromium pairs form preferentially in silver and exhibit electronic structures distinct from isolated platinum and chromium sites, enabling unique surface chemistry,” Jason Weaver, one of the study authors and a chemist at the University of Florida, said. The team then fabricated thin films of the alloys to test whether these predicted atomic pairs actually formed. Building the atomic picture The researchers combined several advanced techniques to examine the catalyst from the inside out. At Brookhaven National Laboratory’s National Synchrotron Light Source II, X-ray absorption fine structure (XAFS) measurements confirmed that platinum and chromium atoms had indeed paired together throughout the silver host. The catalyst’s surface was then analyzed at Sweden’s MAX IV synchrotron using surface-sensitive XAFS and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS), which allowed scientists to observe the catalyst while it was actively converting ethanol. These measurements showed that only catalysts containing platinum-chromium pairs efficiently produced acetaldehyde. Additional scanning transmission electron microscopy (STEM) mapped the distribution of platinum and chromium atoms inside the silver matrix, providing further evidence that the unusual atomic arrangement was responsible for the catalyst’s behavior. “Combining this with the local bonding information from surface-sensitive XAFS gives a really complete picture of the state of the catalyst and how this affects its performance,” Lindsay Merte, one of the study authors and an associate professor of physics at Malmö University, said. Tiny atomic pairs, major gains Catalytic tests showed that the trimetallic platinum-chromium-silver catalyst became active at around 200°C and steadily increased its activity up to 350°C, where it selectively converted ethanol into acetaldehyde and hydrogen, with mass spectrometry identifying these as the dominant gaseous products. In contrast, platinum-silver catalysts accumulated carbon deposits that blocked active sites, while chromium-silver catalysts became less effective because of oxidation. The platinum-chromium pairs greatly suppressed both of these deactivation pathways, allowing the catalyst to remain active for longer. The researchers also found that these heterometallic pair sites stayed stable even at relatively high active-metal loadings, addressing a common limitation of many atomically dispersed catalysts. Previous studies had suggested that carefully designed pairs of different metals could outperform isolated single atoms, but this work provides experimental evidence that such heterometallic pair sites can operate under realistic reaction conditions. A new strategy for catalyst design The study offers a new blueprint for catalyst design. Instead of searching for entirely new materials, scientists may be able to create longer-lasting, more selective catalysts simply by arranging familiar metals in new atomic partnerships—a strategy that could benefit not only ethanol dehydrogenation but many other industrial chemical reactions as well. However, the catalyst has so far been demonstrated only as a model thin-film system, so additional work will be needed before it can be adapted for industrial reactors. The researchers’ next goal is to translate the same atomic design into high-surface-area nanoparticles, which are better suited for large-scale chemical manufacturing. The study is published in the journal Angewandte Chemie. Recommended ArticlesGet the latest in engineering, tech, space & science - delivered daily to your inbox.Rupendra Brahambhatt is an experienced writer, researcher, journalist, and filmmaker. With a B.Sc (Hons.) in Science and PGJMC in Mass Communications, he has been actively working with some of the most innovative brands, news agencies, digital magazines, documentary filmmakers, and nonprofits from different parts of the globe. As an author, he works with a vision to bring forward the right information and encourage a constructive mindset among the masses.