Deposition followed by etching yields ruthenium nanoframes

Noble metals in the form of hollow nanosized particles with holey walls, so-called nanoframes, have proven useful in catalysis, plasmonics, and nanomedicine. But until now, only a few types have been prepared, including, for example, ones made from gold, platinum, and palladium. The exclusive club just admitted a new member—ruthenium (Nano Lett. 2016, DOI: 10.1021/acs.nanolett.6b00607). Michigan Technological University chemists Xiaohu Xia and Haihang Ye, together with researchers at the University of Texas, Dallas, and elsewhere used a ruthenium chloride solution to preferentially deposit ruthenium on the edges and corners of nanosized palladium octahedral seed crystals. Then they removed the palladium via chemical etching, leaving 2-nm-thick hollow ruthenium octahedrons with numerous openings in the nanoframe walls. Unlike most ruthenium nanocrystals, which form a hexagonal close-packed (hcp) structure, the Ru nanoframes adopt a face-centered cubic (fcc) structure. Two types of catalysis tests—reduction of p-nitrophenol and dehydrogenation of ammonia borane—show that the fcc nanoframes are roughly two to four times as active as hcp Ru crystals of comparable size.