Thermal Stability and CO Oxidation Property of Non-Equilibrium Pd–Ru Alloy Catalyst

Abstract

The thermal stability and CO oxidation activity of a non-equilibrium Pd-Ru alloy obtained by leaching Al-Pd-Ru alloy (3/2 approximant, P 40 phase: Al 72 Pd 16.4 Ru 11.6 (at%)) with 20 mass% NaOH aqueous solution were investigated. When the Pd-Ru alloy was annealed under a He or H 2 atmosphere, phase separation of the Pd-Ru alloy proceeded under H 2 at 500°C, whereas the non-equilibrium state was relatively stable under He at temperatures as high as 500°C. In addition, the Pd-Ru alloy sample annealed under He (at 300 or 500°C) showed substantially greater CO oxidation activity than those annealed under H 2 (at 300 or 500°C). The results suggested that there is a more suitable microstructure of Pd-Ru alloy in the nanocrystals for CO oxidation than the solid solution state or the phase-separated state.