Northeastern University has developed a new material that can be used as a high performance automotive exhaust catalyst

On February 3, 2016, Tohoku University announced that it has collaborated with the Japan Material Research Institute to develop a high-performance automotive exhaust catalyst (nanoporous NiCuMnO) that is completely free of precious metals (rare metals) and rare earth elements (rare earths). If this material is used for automotive exhaust gas catalysts, the material cost can be reduced to about one-hundredth of the original, which is conducive to substantial savings in rare metals and rare earths.

A transmission electron microscope image (left) of a nickel-manganese alloy rolled (left) and a nanoporous NiCuMnO made by selective etching of manganese (right)

Conversion rate of NO with respect to temperature (left) and reduction rate of CO oxidation with respect to temperature (right)

Nanoporous metal refers to a metal that has a nanoporous pore size as a sponge. By selectively etching the solid solution alloy with acid, free nanopores of 50 to 100 nm can be formed. Tohoku University elucidated the principle of catalytic activity of nanoporous metals in 2012 and has been hoping to create new automotive exhaust catalysts by studying high reaction yields and high durability.

A 400-degree durability test result of a dollar reaction within 10 days

Transmission Electron Microscope Images of Nanoporous NiCuMnO, Initial (Left) and Post Reaction (Right)

The nano-porous NiCuMnO metal composite compound developed this time was obtained by selective etching of manganese from a solid alloy of copper, nickel, and manganese. This material is highly active for CO oxidation and NO reduction reactions. Compared with the original nickel and copper catalysts, the activity of the catalyst at low temperatures is high. No harmful NO was seen in a 10-day, 400-degree durability test. The CO gas is released and converted to CO2. It has been confirmed that this material is also suitable for mass production. A large number of catalysts can be produced by mass-producing fine powders of copper, nickel, and manganese alloys and immersing these powders in acid.

In an environment-controlled ultrahigh-voltage electron microscope (a type of transmission electron microscope in which a gas is introduced around a reagent, which can be observed under a high-pressure environment), the microscopic structure of the material is automatically changed under the induction of a catalyst reaction. This is the first time in the world to observe NO-reactions under a transmission electron microscope. This fine structure is a combination of active metals (Cu and CuO) and a nanoporous NiMnO network. It can be found that as the protagonist of activity, the "perimeter" of the interface between active metal and oxide is more than 10 times that of the original nanoparticle catalyst. Times. In addition, it is durable at high temperatures due to its thermally stable nanoporous NiMnO network.

This is part of the "Strategic Innovation Research Promotion Business" of the Japan Science and Technology Agency (JST). The results of this study were published on the online version of Advanced Functional Materials, the German international scientific journal, on February 3 (German time). In the future, based on the catalyst design guidelines obtained this time, we will develop automotive exhaust catalysts with higher activity and higher durability, and strive to become practical in a few years. In addition, it will also be dedicated to applying it to methane conversion catalysts (from methane to useful energy resources). (Reporter: Kudo Daisuke)