Gas-switch reduction enables alloying in supported catalysts

Supported catalysts are systems in which the active catalytic materials, such as metals, are dispersed on a solid support material, such as alumina, silica, etc. These catalysts are widely used in various chemical processes. Several methods are available for preparing supported catalysts. Among these, the simple impregnation method is particularly suited for industrial settings. In this method, metal precursors and oxide supports are mixed, dried, and crystallized via heat treatment under certain gases. Various high-performance supported catalysts have been prepared using impregnation.

However, this method has mostly been used to synthesize conventional monometallic catalysts, which perform well only for specific chemical reactions. Given the limited number of metal catalyst and oxide support materials and the growing demand for advanced catalytic reactions, there is a need to explore new methods that enhance the diversity and performance of supported catalysts. Metal alloying is a promising method for achieving this. Random alloying can dramatically change both the structure and catalytic behavior of metals by combining their divergent properties. Yet, alloying metals is challenging, especially for immiscible metals, requiring complex methods. For industrial processes, simpler and more scalable methods are desirable.

In a breakthrough, a Japanese research team led by Assistant Professor Yoshihide Nishida from the Advanced Ceramics Research Center at Nagoya Institute of Technology successfully demonstrated simple impregnation-based alloying of an immiscible ternary rhodium–palladium–platinum (Rh–Pd–Pt) system on non-reducible alumina (Al₂O₃) via an innovative gas-switch-triggered reduction method. “A key idea in our research is that oxide supports, like alumina, have exceptional heat resistance,” explains Nishida. “This means that metal precursors can be stably held on the support at high temperatures. A simple gas switch can then trigger the simultaneous reduction of all metals, instantly alloying them despite their immiscibility.”

The team included Takaaki Toriyama and Tomokazu Yamamoto from Kyushu University, and Katsutoshi Sato and Katsutoshi Nagaoka from Nagoya University, and Masaaki Haneda from Nagoya Institute of Technology. Their study was published in Catalysis Science & Technology on August 15, 2025.

The core principle of alloying immiscible metals, according to previous studies, involves simultaneous co-reduction of all metal cations. To streamline this process for supported catalysts, the researchers integrated it into the impregnation process via a gas-switch-triggered reduction method. In conventional impregnation, only hydrogen (H₂) is supplied during heat treatment to reduce the metal cations. However, this results in sequential reduction, limiting alloying. In contrast, the new method begins with an inert gas, like argon (Ar), during the initial temperature increase. Then, at a sufficiently high temperature, around 600°C, where Rh, Pd, and Pt can all be reduced, the gas is switched to H₂, triggering simultaneous reduction and alloying. Using this method, the researchers successfully prepared an alloyed RhPdPt/Al₂O₃ supported catalyst, with metal precursors in an equimolar ratio.

Through X-ray absorption spectroscopy (XAS), the researchers confirmed the alloying of the metals in the prepared catalyst. In contrast, in the samples prepared using conventional impregnation, the metals retained their individual characteristics, indicating insufficient alloying. To validate the generalizability of the method, the researchers also prepared additional catalysts: bimetallic PdPt/Al₂O₃, trimetallic RhPdPt/SiO₂, as well as RhPdPt/Al₂O₃ with varied metal compositions. The results confirmed general applicability, while also highlighting potential limitations under certain support and metal compositions, which the researchers explained can be overcome by optimizing process parameters.

Notably, they also observed that the metals alloyed using the gas-switch-triggered reduction method were prone to oxidation when exposed to air, which can restructure the particles. To prevent this, the researchers recommend merging it into the pretreatment process before catalyst evaluation, allowing in situ alloy formation without oxidation.

The prepared RhPdPt/Al₂O₃ supported catalyst demonstrated an impressive 18 times higher catalytic performance in nitrile hydrogenation compared to monometallic catalysts. Furthermore, the proposed method does not require any specialized equipment or procedure, making it highly suitable for industrial processes.

“This proposed gas-switch-triggered reduction method is simple, scalable and has the potential to significantly reduce energy consumption in chemical manufacturing,” says Nishida. “This will lead to more sustainable production of chemicals, pharmaceuticals, and fuels essential in our daily lives.”

We hope this method becomes commonplace in industry, accelerating the shift toward greener and more efficient chemical synthesis.

About Nagoya Institute of Technology, Japan

Nagoya Institute of Technology (NITech) is a respected engineering institute located in Nagoya, Japan. Established in 1949, the university aims to create a better society by providing global education and conducting cutting-edge research in various fields of science and technology. To this end, NITech provides a nurturing environment for students, teachers, and academicians to help them convert scientific skills into practical applications. Having recently established new departments and the “Creative Engineering Program,” a six-year integrated undergraduate and graduate course, NITech strives to continually grow as a university. With a mission to “conduct education and research with pride and sincerity, in order to contribute to society,” NITech actively undertakes a wide range of research from basic to applied science.

Website: https://www.nitech.ac.jp/eng/index.html

About Assistant Professor Yoshihide Nishida from Nagoya Institute of Technology, Japan

Dr. Yoshihide Nishida is currently an Assistant Professor at the Advanced Ceramics Research Center, Nagoya Institute of Technology. He received his master’s degree from Oita University in 2018 and Ph.D. degree from Nagoya University in 2021. His research interests include heterogeneous catalysts, nanomaterials, catalytic processes, and resource chemistry among others. His articles have received over 430 citations so far.