Single-atom catalysts reach record-breaking density

Researchers have prepared single-atom catalysts with 10 times as many metallic centers as previous attempts (Nat. Nanotechnol. 2021, DOI: 10.1038/s41565-021-01022-y). In single-atom catalysts, individual metallic atoms are dispersed on a solid support, with each atom available to catalyze a reaction. At high catalyst loadings, however, it is hard to keep the atoms isolated and prevent metallic clusters from forming. Most single-atom catalysts average between 1% and 2% loading—a measure of catalyst concentration on the support. “Our approach enables single-atom catalysts with up to 23% metal content by weight,” says Javier Pérez-Ramírez of the Swiss Federal Institute of Technology (ETH), Zurich, who co-led the study with Jiong Lu of the National University of Singapore. “It works with most first-row transition metals, as well as with noble metals like ruthenium, iridium, and platinum, all of which have extensive applications in heterogeneous catalysis,” Pérez-Ramírez adds. The new catalysts were produced by introducing a two-step annealing process, which tunes the material’s properties via heat treatment. In the first step, a low-temperature treatment allows metals bound to ligands to anchor on the support surface in a controlled way and thus prevents metal clusters from forming. A subsequent, higher-temperature step removes the ligands, leaving just the metals. “This method is robust, versatile, and scalable,” Lu says. Studies of automated synthesis gave similar yields, which could help with scale-up, he adds.