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Elemental maps obtained by HAADF-STEM. It can be seen that Pd and Ru have the same distribution in the interior of the nanoparticles, and a solid solution mixed at the atomic level is obtained.
Results of NOx purification performance evaluation of PdRu-NPs catalyst and comparative catalyst. PdRu-NPs exhibited catalyst performance comparable to that of Rh. The NOx purification performance at low temperatures exceeded Rh.
The research team consisting of Japan’s Oita University, Kyushu University, Kyoto University, etc. announced on June 24, 2016 that it has been found that the solid-solution alloy nanoparticles of palladium (Pd) and ruthenium (Ru) mixed at the atomic level show a relationship with Rh (Rh). ) For the same degree of car exhaust purification performance. Rh is a precious metal, rare and expensive, and more than 80% of its global production is used for gasoline vehicle three-way catalysts. Therefore, users are demanding the development of new substances that can replace Rh.
The team aimed at Pd and Ru on both sides of Rh in the periodic table. These two elements are rich in resources and low in price compared with Rh. Therefore, as long as an alloy that mixes these two elements at an atomic level is produced, it is expected to form a new inexpensive material with similar properties to Rh.
In the previous studies, PdRu and NP were mixed using atomization and chemical reduction to synthesize PdRu solid solution alloy nanoparticles (PdRu-NPs) at an atomic level. This time, a supported catalyst using PdRu-NPs was developed to evaluate the performance of the catalyst in the representative use of the Rh catalyst, namely the automobile exhaust gas purification reaction.
As a result, it was found that nitrogen oxides (NOx) that are difficult to clean with a catalyst other than Rh at low temperatures can be effectively removed using PdRu-NPs, and the alloy shows very high catalyst performance, and its level is comparable to that of Rh even below 200C. The temperature can also exceed Rh in the temperature range. In addition, PdRu-NPs also exhibit very excellent catalyst performance for removing off-gas components other than nitrogen oxides (carbon monoxide, propylene).
The research team theoretically studied the electronic structure (state density) of the PdRu alloy based on the density functional theory. It was found that the electronic structure of the PdRu alloy has characteristics similar to those of Rh. In addition, this property was first discovered by mixing Pd and Ru at an atomic level. This result shows that PdRu-NPs act as "like metalloids" that have the same properties as Rh in electronic structure, thereby promoting the decomposition of NO.
PdRu solid solution nanoalloys can be used not only as automotive catalysts, but also as a gallium-like metal in a variety of uses and fields where Rh is currently used. In addition, the results of this study also show that by mixing the alloy with other elements at the atomic level, the properties and characteristics of the target element (DOS process) can also be achieved. In the future, it is hoped that by combining multiple elements to reproduce the characteristics of rare elements, it will be helpful to develop new substances that have more functions than existing elements.
The relevant research results were published in the "Scientific Reports" electronic journal under the Nature Publishing Group on June 24, 2016 (UK time). (Special Contributor: Kudosuke)
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