Ir-Catalysed Nitrous oxide (N 2 O) Decomposition: Effect of Ir Particle Size and Metal–Support Interactions

Abstract

The effect of the morphology of Ir particles supported on γ-Al₂O₃, 8 mol%Y₂O₃-stabilized ZrO₂ (YSZ), 10 mol%Gd₂O₃-doped CeO₂ (GDC) and 80 wt%Al₂O₃–10 wt%CeO₂–10 wt%ZrO₂ (ACZ) on their stability on oxidative conditions, the associated metal–support interactions and activity for catalytic decomposition of N₂O has been studied. Supports with intermediate or high oxygen ion lability (GDC and ACZ) effectively stabilized Ir nanoparticles against sintering, in striking contrast to supports offering negligible or low oxygen ion lability (γ-Al₂O₃ and YSZ). Turnover frequency studies using size-controlled Ir particles showed strong structure sensitivity, de-N₂O catalysis being favoured on large catalyst particles. Although metallic Ir showed some de-N₂O activity, IrO₂ was more active, possibly present as a superficial overlayer on the iridium particles under reaction conditions. Support-induced turnover rate modifications, resulted from an effective double layer [O^δ−–δ⁺](Ir) on the surface of iridium nanoparticles, via O²⁻ backspillover from the support, were significant in the case of GDC and ACZ.

Graphical Abstract