CO abatement via Ir-based catalysts: effect of the support and preparation method on catalytic activity and stability

Here we report on the effect of the support and preparation method on the activity and stability of Ir-based catalysts under CO oxidation. Alunina-ceria-zirconia (ACZ: 60wt%Al2O3 - 40wt%CexZr1-xO2, x=0.25, 0.5, 0.75) mixed oxide supports with high oxygen storage capacity (OSC) were synthesized via two different methods, hydrothermal (ACZ-H) and co-precipitation (ACZ-P), and used as supports of Ir nanoparticles, so as, besides the Ce/Zr composition to also deal with the effect of the preparation method on catalytic performance. ACZ supports and counterpart Ir/ACZ catalysts were thoroughly characterized using various techniques, while catalytic measurements were conducted under excess O2 conditions (1.0% CO, 5.0% O2, balance He at 1 bar) in the temperature range of 100-400oC. Both pre-reduced and pre-oxidized catalysts were evaluated, while their sintering behavior after experiencing several sequential oxidative thermal aging steps was also studied. The results demonstrated superior textural characteristics (BET surface area and pore volume) of Ir/ACZ-H catalysts as well as stronger interaction of Ir nanoparticles and support particles than that of Ir/ACZ-P, resulting to better CO oxidation efficiency and stability. All catalysts demonstrated stable CO activity after thermal aging, reflecting beneficial influence of ACZ support on the sintering resistance characteristics of Ir nanoparticles.