Researchers have created intermetallic alloy nanoparticles of palladium and zinc, with zinc and palladium atoms arranged alternately. Intermetallic alloys have stronger corrosion resistance than alternative alloys while retaining the electrocatalytic properties of two metals, and can be used to develop new non precious metal electrocatalysts.

Palladium is a precious metal that has attracted much attention as an electrocatalyst for fuel cells, which requires a metal with high electrocatalytic activity. Due to the high cost of palladium, creating palladium zinc alloys should improve catalytic activity while reducing costs. In addition, corrosion resistance is important for potential electrocatalyst materials, as catalytic reactions using highly corrosive alkaline aqueous solutions can degrade metal electrocatalysts and reduce their efficiency over time.

A research team led by Professor Hiroshi Inoue, Associate Professor Eiji Higuchi, and Associate Professor Masanobu Chiku from the Graduate School of Engineering at Osaka City University has discovered a promising palladium zinc intermetallic alloy (i-PdZn). The intermetallic alloy has a precisely arranged atomic structure consisting of an equal amount of alternating palladium and zinc atoms. This results in high corrosion resistance of i-PdZn in alkaline aqueous solutions.

Metal alloys can be alternative alloys or intermetallic alloys. In the replaced palladium zinc alloy, zinc atoms randomly replace half of the palladium atoms, while in the new intermetallic alloy i-PdZn, palladium and zinc atoms are arranged in an alternating manner, so that each zinc atom is surrounded by palladium atoms, and vice versa.

When both i-PdZn and substituted palladium zinc alloys were immersed in an alkaline solution, researchers found that within a few minutes, most zinc atoms leached out of the substituted alloy. However, the regular arrangement of palladium and zinc atoms in i-PdZn effectively prevents the leaching of zinc atoms in the alloy. This forms a protective framework palladium shell outside the alloy, giving i-PdZn higher corrosion resistance.

In addition, when used as an electrocatalyst for ethanol oxidation, the peak activity of i-PdZn is about 5.1 times that of pure palladium. This is due to the electronic properties of the alloy core and the larger surface area generated by the skeleton palladium shell in alkaline aqueous solutions.

Professor Inoue summarized, "The unique properties of intermetallic alloys make them excellent catalysts, as previously known, but now we have demonstrated that the dissolution of zinc in our intermetallic palladium zinc alloys is greatly inhibited, making them more corrosion resistant than alternative alloys." We believe these results may provide clues for the development of non precious metal electrocatalysts, as corrosion resistance is an issue