Succeeding in synthesizing intermetallic compound of "metastable phase" — Paving the way for creating new functional materials via electrochemical reactions

Intermetallic compounds, in which two or more metallic elements are regularly arranged at fixed composition ratios, are used in a wide range of applications, including catalysts and electronic materials. In particular, intermetallic compounds in metastable phases, which are not thermodynamically stable, are attracting attention as potential new functional materials because they can exhibit unique electronic states and reaction characteristics. However, synthesizing metastable compounds is generally difficult because they readily transform into more stable states.

A research team led by Assistant Professor Soichi Kikkawa at the Graduate School of Science, Tokyo Metropolitan University, successfully synthesized CuIn₂, a metastable copper (Cu)-indium (In) intermetallic compound, in nanoparticle form using electrochemical reactions. The researchers focused on a complex metal oxide (Cu₂In₂O₅) that contains Cu and In uniformly distributed at the atomic level. Using Cu₂In₂O₅ as an electrocatalyst, they reduced the material through electrochemical reactions and analyzed samples before and after reduction using X-ray diffraction and electron microscopy. The results revealed the formation of not only the thermodynamically stable intermetallic compound Cu₂In, but also the metastable intermetallic compound CuIn₂. Furthermore, evaluation of the obtained particles for carbon dioxide (CO₂) reduction showed that hydrogen (H₂) evolution was significantly suppressed, while carbon monoxide (CO) and formate (HCOO⁻) were produced.

This achievement demonstrates a new route to producing intermetallic compounds with previously inaccessible compositions and structures through electrochemical reactions. In addition, the CuIn₂ obtained in this study may prove to be a promising new catalyst for converting carbon dioxide (CO₂) into useful resources.

(Article: Masanori Nakajo)