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, P₄₀ phase: Al₇₂Pd_16.4Ru_11.6 (at%)) with 20 mass% NaOH aqueous solution were investigated. When the Pd–Ru alloy was annealed under a He or H₂ atmosphere, phase separation of the Pd–Ru alloy proceeded under H₂ 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 H₂ (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.