Improved hydrogen oxidation reaction under alkaline conditions by ruthenium-iridium alloyed nanoparticles

Carbon supported Ru-Ir (Ru-Ir/C) catalysts with their alloyed nanoparticles and those mainly having segregated Ru and Ir nanoparticles were prepared. The Ru-Ir alloyed nanoparticles improved the hydrogen oxidation reaction (HOR) activity under alkaline conditions in comparison with the segregated Ru and Ir nanoparticles as well as Ru/C and Ir/C. Furthermore, the HOR activity of Ru-Ir alloyed nanoparticles was ca. four times higher than that of Pt/C. The cause of the enhanced HOR activity of Ru-Ir alloyed nanoparticles was investigated in terms of the hydrogen-binding energy (HBE). It was found that the HOR activity increases with a decrease of the HBE, and Ru-Ir alloying lowers the HBE in comparison with the segregated Ru-Ir nanoparticles and Ir/C. Therefore, the lowered HBE by Ru-Ir alloying was considered to be responsible for the high HOR activity of Ru-Ir alloyed nanoparticles.